Reducing Risk
    in  Paint Stripping
Proceedings of an International Conference

          February 12-13, 1991
           Washington, D.C.
         Economics and Technology Division
           Office of Toxic Substances
        U.S. Environmental Protection Agency
             Washington, D.C.

        Proceedings of an

International Conference on
               in Paint Stripping
       February 12-13, 1991
       Omni Shoreham Hotel
         Washington, D.C.
    Economics and Technology Division
       Office of Toxic Substances
   U.S. Environmental Protection Agency
           Washington, D.C.

Prepared by JT&A, inc.,  and Abt Associates for the Office of Toxic Substances, U.S.
Environmental Protection Agency. Points of view expressed In this proceedings  do not
necessarily rejlect the view or policies of the U.S. Environmental Protection Agency or any
of the contributors to this publication.  Mention of trade names and commercial products
does not constitute endorsement of their use.
             Conference Planning Committee
             Jean E. (Libby) Parker, Susan Krueger, and Dan Axelrad
                        Economics and Technology Division
                            Office of Toxic Substances
                       U.S. Environmental Protection Agency
                            401 M Street, SW (TS-779)
                             Washington, D.C. 20460
                                (202) 382-3670

                        John Gruber and Vicki Hutson
                                Abt Associates
                        4800 Montgomery Lane, Suite 500
                           Bethesda, Maryland 20814
                                (301) 913-0500

                      David Trouba and Judith Sutterfield
                                  JT&A. Inc.
                       1000 Connecticut Ave., NW, Suite 802
                             Washington, D.C. 20036
                                (202) 833-3380
                       Project Manager: Lura Taggart Svestka
                             Editor: Gretchen Flock
                  Typesetting and production: Jaye Douglas Isham
                             Cover art Patricia Perry
                     Cover and text printed on recycled paper.

            Copies of this proceedings may be ordered from:

                                 JT&A, inc.
                         1000 Connecticut Ave., Suite 802
                            Washington, D.C. 20036
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            _                       -

Introduction   	vii
Mark Greenwood

Foreword	ix


Introductions and Opening Remarks	3
Mary Ellen Weber, Linda Fisher, and Charles Auer

U.S. Federal Government Activities—Panel	9
Mary Ellen Weber, Paul Campanella, Sandra Eberle, Fayez Hanna, and Robert Rosensteel

OECD Activities Overview—Panel
   The Canadian Approach to Regulating Paint Strippers  	13
   George Long

   Regulation of Methylene Chloride in the United Kingdom	15
   Bill Holmes

   OECD Risk Reduction Activities: A Process for Cooperative Work on
   Specific Chemicals  	17
   Victor Morgenroth

Labor's View on Reducing Risk in Paint Stripping	19
John B. Moron

Product Stewardship—Panel
   Product Stewardship and Chemaware at Dow  	21
   William C. Hayes

   Controlling Paint Stripping Emissions	23
   W. Platklewlcz


Current Paint Stripping Practices

Pollution Prevention Case Study: Methylene Chloride Substitution in an
Automotive Plant  	27
Jack Davis and William Relchert

An Overview of Paint Stripping Practices in the Metalforming  Industries	32
John F. Grainger

Substitute Solvent & Non-solvent Alternatives

NMP Formulations for Stripping in the OEM Market Sector	39
Carl J. Sullivan


Aromatic Solvent Strippers for Automotive Paint Booth Maintenance  	44
Harry Seifert

Alternative Methods for Uncured Paint Removal In Automotive
Manufacturing	47
R. Jeff Meade and Frank C. Burinsky

Cryogenic Paint Stripping	60
Ashok N, Mathur

Use of Plastic Media Stripping in Original Equipment Manufacturers'
Applications 	53
Joseph E. Konopka

Ultra High-pressure Water for Paint Removal in the Original Equipment
Manufacturing Sector	59
Al Hlrsch

Exposure Control & Pollution Prevention

Practical VOC Reduction	65
Thaddeus J. Fortln

The Sponge Jet System—Environmental Ramifications	68
Bill Lynn

Recycling Methylene Chloride: Optimizing the Waste Stream   	70
Peter R. Morton

Questions & Discussion	75

Current Paint Stripping Practices

Paint Stripping Alternatives for Aircraft	79
William D. Stevens

Media Blast Dry Paint Stripping: The Only Environmentally Safe Process  	82
Robert Peru// and Charles Owens

Substitute Solvent & Non-solvent Alternatives

Envirostrip Starch Blast Media—A Safe, Economical Alternative to
Methylene Chloride Strippers	93
Ruben Lenz and John Oestrelch

Crystalline Ice Blasting	•	95
Sam Vlsalsouk

ARMEX/ACCUSTRIP Bicarbonate Blasting  	TOO
Gene McDonald

The Good, the Bad, and the Ugly—But, for a Few Dollars More	105
Robert M. Carnes

Perspectives on Surface Preparation with COa Blasting   .......................  117
Scott Stratford
Water as a Tool: Alternative Methods of Reducing the Environmental and
Human Health Risks In Paint Stripping  .................................
Frank E. Scharwat
CO2 Pellet Blasting for Paint Stripping and Coatings Removal ....................  124
Wayne N, Schmltz
Pulsed Light Flashlamp System for Paint Removal in Maintenance Stripping  ............  126
Anthony P. Trlppe
The Polygon Paint Removal System  ..................................  1 29
David Van Alstyne
Automated Laser Paint Stripping  ....................................  132
Paul Lovoi
Exposure Control 6i Pollution Prevention
Waste Minimization for Army Depot Paint Stripping Operations ...................  137
Ronald P. Jackson, Jr.
The Blodegradatlon of Paint Waste  ..................................  143
Gall Bowers-Irons, Robert Pryor, Craig Miller, and Trung Chau
Vapor Recovery and Recycling of Methylene Chloride from Paint
Stripping Applications  ..........................................  146
Paul £. Scnelhlng
Questions 81 Discussion .....................................  151
Current Paint Stripping Practices
Current Practices and Processes for Paint Stripping in Professional
Furniture Refinishlng  	155
Tim B. Inman
Do-it-yourself Paint Stripping Practices: The Household Market  	159
Mark A. Monlque
Comparative Performance of Substitute Paint Stripper Formulations	163
Janet C. Hlckman
Substitute Solvent 8l Non-solvent Alternatives
DBE-based Stripper Formulations	173
Harold L Jackson
Surface Tension Modification of NMP-based Paint Strippers	177
William C. Walsh

Woodfinisher's Pride: An Alternative to Current Chemical Paint Strippers  	185
Steve Johnson

Bix Stripper: An Alternative to Methylene Chloride	191
Gerald L. Blxenman

Substitute Chemical Formulations for Professional Furniture Refinishlng	192
David L. White

An Alternative to Methylene Chloride for Removal of Lead-based Paint  	195
Stephen C. Arndt

Exposure Control & Pollution Prevention

Case Study: Control of Methylene Chloride Exposures During Commercial
Furniture Stripping   	199
Cheryl L. Falrfield and Amy A. Beasley

An Investigation of the Reduction of Methylene Chloride Volatility in Paint Strippers	201
Eric L. Mainz

Questions and Discussion  	213
Closing Session
Panel Reports: Summary of Findings  	217
Christine Whittaker, James Gideon, and Sandra Eberle

The Next Steps: Planning for the Future   	222
Katy Wolf

Closing Summary	227
Mary Ellen Weber
Appendix A:  Attendees List	229

Appendix B:  Supplemental Information  	241

       The International Conference on Reducing Risk in Paint Stripping represents
       the first in a series of planned meetings and exchanges sponsored by the
       Office of Toxic Substances at the U.S. Environmental Protection Agency (EPA).
It is my belief that the exchange of information among individuals from Industry and
government, both domestic and international, represents one of the most efficient and
effective methods of achieving our goals of reducing human health risks and
environmental pollution.

   I am grateful for the enthusiastic response of participants at this conference. Many
of you who took part in the discussions remarked that you were pleased with the new
cooperative initiatives taken by EPA to promote information sharing and learn about
industry developments in risk reduction. It is my hope that information gained at the
conference will translate into new developments in industrial technologies. In addition,
I hope this exchange of ideas will lead to the realization of opportunities to use existing
risk reduction technologies while still meeting the technical needs for coatings removal.

   The Office of Toxic Substances would like to thank all those who participated from
both the private and public sectors. In particular, we thank the international
participants who attended the conference from Australia, Canada, France, Germany,
Japan, the Netherlands, Switzerland, and the United Kingdom. I would like to extend
our special thanks to those agencies that helped to coordinate  the program and chair
the individual technical sessions: the U.S. Consumer Product Safety Commission, the
National Institute for Occupational Safety and Health, and the  Occupational Safely
and Health Administration.

   Finally, for those of you who came away from the paint stripping conference with
new contacts in government and industry or new processes for application to
industrial paint stripping needs, we would like to hear from you. Specifically, we would
appreciate any information that documents changes in your industry, business
practices, or thinking about pollution prevention that were instituted as a result of
attending this conference. Have you changed a process or added any new equipment
for coatings removal or paint stripping waste management, taken any additional
measures to reduce solvent exposures in the workplace, or tried any new substitute
chemicals or paint removal processes to evaluate their effectiveness? Let us know how

                                      vii                    ——

your efforts in pollution prevention and risk reduction have been furthered as a result
of this conference. We are eager to continue the communication process and expand
on the transfer of information. Please contact the Office of Toxic Substances to share
details of your progress in pollution prevention and risk reduction.

   Thank you again for your cooperation in this new endeavor. We will hope to hear
from you and look forward to hosting additional technical information sharing
conferences in the future.
                                 Mark Greenwood
                                 Office of Toxic Substances
                                 U.S. Environmental Protection Agency
                                 Washington, D.C.

       The International Conference on Reducing Risk in Paint Stripping was held on
       February 12-13, 1991, in Washington, D.C. Sponsored by the U.S.
       Environmental Protection Agency, cooperation and support from the National
Institute for Occupational Safety and Health, the U.S. Occupational Safety and Health
Administration, the U.S. Consumer Product Safety Commission, and the Halogenated
Solvents Industry Alliance helped prbduce a productive and successful conference.

   This conference focused on managing the use of chemical paint strippers and was
intended to identify and promote ways to reduce risks associated with these paint
strippers. Serving as a forum for discussion of exposure controls, paint stripper
substitutes, and alternative technologies, topics included substitutes for methylene
chloride paint strippers; product stewardship programs of methylene chloride
producers; opportunities for pollution prevention in paint stripping; and government
activities in the United States and other countries. Conference participants included
an international group of chemical producers, paint stripper formulators and users,
producers of mechanical and other alternative paint stripping technologies, public
interest groups, and government officials.

   These proceedings contain transcribed talks and copies of the papers presented
during the conference. The conference format included both plenary and breakout
sessions to address concerns in original equipment manufacturing, maintenance
usage, and consumer and household usage. This format is reflected in the
organization of these proceedings. Presentations provided to us in written form are
included in these proceedings. Typed summaries of the verbal remarks made at the
conclusion of the breakout sessions  also have been included to provide a more
complete picture of the information and views exchanged. An opportunity was provided
for the inclusion of information not presented during the conference; these additional
papers can be found in Appendix B: Supplemental Information.


Introductions  and Opening  Remarks
Mary Ellen Weber
Office of Toxic Substances
Linda Fisher
Office of Pesticides and Toxic Substances
Charles Auer
Existing Chemical Assessment Division, Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C.
m Mary Ellen Weber
As  the  recently  appointed director of the
Economics and Technology Division in the Office
of Toxic Substances, I'm delighted to welcome all
of you to our first international  conference on
reducing risk in paint stripping.
    At the Environmental Protection Agency (EPA),
the  Office of Toxic  Substances is responsible for
carrying out the Toxic Substances Control Act.
Specifically, we manage the use of chemicals in
such a way that society can reap their benefits
without facing unreasonable risks.
    We at EPA, along with our sister national and
international agencies, are increasingly concerned
about the risks to human beings who are exposed
to methylene chloride and other  chemical sub-
stances associated with paint stripping. Therefore,
we  are excited to learn about new developments
that make it possible to both reduce risks and
prevent pollution. Now in its third decade, EPA is
concentrating increasingly on pollution prevention
and risk reduction as complements to our tradi-
tional policy of end-of-the-pipeline treatment.
    The purposes of this conference, therefore, are
to share information, promote the transfer of tech-
nology, and present and compare costs and tech-
nical  feasibilities  of alternative methods and
approaches to paint stripping. It is not the purpose
of this conference to discuss specific risk numbers.
    Before Joining EPA, I spent a number of years
at the Occupational Safety and Health Administra-
tion (OSHA), where  I conducted economic and
technological feasibility analyses. At OSHA, I had
the pleasure of working closely with my counter-
parts at the Consumer Products Safety Commis-
sion and the National Institute for Occupational
Safety and Health. I want to thank OSHA, CPSP,
and NIOSH for their participation in this con-
ference. We're grateful for their support and their
help in coordinating other federal agencies and
identifying participants and speakers.
   In a few minutes, I will have the privilege of
introducing my boss's boss, but before that. I'll run
briefly over the agenda.
   We will begin the conference by looking at an
overview of the risk considerations associated with
paint  stripping. After  that, we will  hear  how
various U.S. government agencies are attempting
to reduce risks associated with paint stripping.
   Today, pollution problems are international in
scope. For that reason, we have a panel who will
discuss the Organization for Economic Coopera-
tion and Development's (OECD's) activities regard-
ing paint  stripping and pollution  prevention
approaches and techniques. Labor will then speak
to us about concerns for workers' exposure. Final-
ly, we will hear from a panel,  appropriately con-
ducted by industry, on product stewardship.
Product stewardship is a new idea at EPA; it
involves taking responsibility for  the entire life
cycle of a chemical. No longer are we just interested
in cleaning things up. We want to follow the chemi-
cal from its birth to its disposal—to be responsible
for the chemical throughout its life cycle of produc-
tion, distribution, and use.
   This afternoon and tomorrow morning, we will
be splitting into three groups:  original equipment
manufacturing, maintenance,  and household and
commercial. The panel discussions will focus on

reviewing current paint stripping practices, alter-
nate chemicals and  other  technological sub-
stitutes, and various risk reduction and pollution
prevention techniques for each of these sectors.
Tomorrow afternoon when we meet In full session,
we will summarize what we have learned In these
panels. We will concentrate on what we can take
home with us  and apply, such as techniques,
methodologies,  and risk reduction opportunities
we have learned here.
    We plan to  produce proceedings of this con-
ference and want to include as much Information
as possible. We encourage all of you who have
information of a  technical nature—product
specification, cost Information, feasibility informa-
tion of alternative methodologies, techniques, and
products—to give it to  our  contractor, Abt As-
sociates. In that way, we can promote our goal of
sharing information and disseminating it as much
as possible.
    Now, I have the pleasure of telling you a little
bit  about Linda Fisher. Linda  is the assistant
administrator for the Office of Pesticides and Toxic
Substances (OPTS) at EPA. Before that, she was
the assistant administrator for the Office of Policy
Planning and Evaluation. Linda Joined EPA as the
chief of staff and special assistant to former Ad-
ministrator Lee Thomas. Before coming to EPA,
she was an associate staff member for the House
Appropriations Committee and a legislative assis-
tant in the offices of Congressman Ralph Regula
and Congressman Clarence Brown. A native  of
Columbus, Ohio, Linda is a graduate of Miami
University; she  received an  MBA from George
Washington University and  earned  a juris doc-
torate degree from Ohio State University's College
of Law In 1982. She is a member of both the Ohio
and D.C. bars. It's an honor and a pleasure to work
for  a woman of high integrity and  intellectual
acumen—and, best of all, she has a terrific sense
of humor.

• Linda Fisher
Again, I'd like to welcome all of you to our con-
ference and to extend a special warm welcome to
our international visitors. We really appreciate you
    Our conference here today does reflect a major
change in and  approach to  managing chemical
risks in the United  States. The Toxic Substance
Control Act (TSCA). the statute under which we
regulate chemicals,  Is one of the  most powerful
that EPA administers. Our office Is responsible for
managing and assessing the  risks of over 60,000
industrial chemicals.  How  we identify hazards
from these chemicals, how we assess risks, and
how we manage them pose increasingly complex
problems. More and more we find ourselves asking
questions such as: What are the safer substitutes
for these chemicals? How can we encourage people
to use them? Are  there better ways to reduce
exposure than we have Identified in the past?
    As we all know,  the typical "command and
control" approach that we have so often used at
EPA is slow and tedious—frustrating for the con-
sumer, the government regulator, and Industry.
New concepts in risk reduction are needed—and
this conference will illustrate some that are of
growing importance to EPA.
    The first of these concepts Is pollution preven-
tion. It is not end-of-pipe control, designed to
minimize harm from pollution  after it has been
created. Instead, more and more at EPA, we are
asking the question, how can we prevent the pol-
lution, or the risk from pollution, from occurring
in the first place?
    We also are  beginning to examine chemical
hazards from a broader base  than before: we are
examining risks to consumers, to workers, and to
the environment and  trying to focus broadly,
rather than shifting the risks from one medium to
another or from one population to another.
    We are also Increasingly aware of the Impor-
tance that Information sharing can play In reduc-
ing risks. Government agencies sharing  their
information with each other and with Industry and
both of us sharing our information with the public
oftentimes can create very successful risk reduc-
tion opportunities.
    Lastly, more and more we see the importance
of International cooperation—rarely Is an environ-
mental problem limited to one country. Technical
work on risk assessment and risk reduction tech-
nologies can be shared between Industrialized na-
tions.  This  will help develop cooperative and
consistent actions that will reduce duplication of
efforts and perhaps achieve better risk reduction
for citizens of all countries.
    So how did we choose paint stripping, and why
methylene chloride? First of all, we thought this
chemical and particular usage lend themselves to
some  of our new and creative approaches. Our
concern with methylene chloride  began in the
mid-1980s when it was found to be carcinogenic
to animals. EPA and other U.S. regulatory agen-
cies,  as well  as regulatory  bodies in other
countries, began assessing the risks to human
health of methylene chloride In several uses. Since
the process of paint stripping resulted in high
exposures to  this chemical, EPA  and other
regulatory agencies studied risk management ac-

                                                                      Reducing Risk In Paint Stripping
tlvltles, looking at available substitutes and ex-
posure controls. We focused on three categories:
the original  equipment manufacturer,  main-
tenance, and consumer usage.
   Today, after several years of examination by
government regulators, government users, and
Industry, significant questions about what we can
and should do to  reduce paint stripping risks
remain. We know there are many substitute sol-
vents  in use or under consideration for use, but
there are lots of questions about their effectiveness
and If they create health hazards.
   We know alternative  technologies are being
developed, but we don't always know how effective
they are.  In many applications where methylene
chloride is still used, exposure-reduction methods
have either not been discovered or have not been
carried out. There are still so many unknowns—
that Is the primary reason for staging this con-
ference. We are trying to promote the search for.
and research Into, safe and effective  ways to
reduce risk from methylene chloride paint ^strip-
pers.  This conference Is our first attempt  to use
this medium  to encourage cooperation between
industry  and  government to reduce risks and
prevent pollution in the first place. If It is true that
information is power, then this exchange of infor-
mation among national and  international sup-
pliers, users,  and government  representatives,
may solve the problem of reducing unnecessary
exposure to and risk from paint strippers.
   We hope those attending this conference will
take home new ideas and new friendships that can
be used in the future to Identify ways to reduce
and manage risks and to prevent pollution in paint
stripping applications. I wish you good luck In this
conference, and I hope it is beneficial to all.

• Mary Ellen Weber
Thank you very much, Linda. I am happy to Intro-
duce Charles Auer—Charlie is currently the direc-
tor of the Existing Chemical Assessment Division
In OTS. Before that, he was deputy director of the
Health and Environmental  Review Division at
OTS.  A chemist and a lexicologist, Charlie has
extensive experience in hazard and risk assess-
ments on experimental and existing chemicals.
    Charlie is the OTS lead in International ac-
tivities for EPA and a major liaison with the OECD.
He has been actively Involved in cooperative test-
ing and assessment of high production volume
chemicals and Is instrumental In developing inter-
national approaches to hazard and risk assess-
ment. And now Charlie will talk to us about risk
factors associated with paint stripping.
• Charles Auer
I, too, would like to welcome everyone here. And,
repeating what the two preceding speakers have
said, I hope this conference will stimulate an ex-
change of views and increase understanding on
the question of substitutes for methylene chloride
paint strippers.
   My subject is the  risk considerations in
evaluating paint  stripping alternatives to
methylene chloride.  The conference's focus is on
managing the use of chemical paint strippers by
exposure controls, pollution prevention techni-
ques, chemical substitutes,  and alternative tech-
   Discussion of risk is not a major focus of this
conference, but I think we need to understand the
kinds of information that will be most helpful in
our search to develop alternative paint strippers
so that we can advance to new products that  will
have fewer risks than methylene chloride.
   When we evaluate methylene chloride and its
alternatives, we must consider health and environ-
mental hazards as well as the exposure potential
of the various materials. We need to know the full
range of risks from chemical  toxicity to safety
aspects. For instance, major concerns in the safety
aspects of many of the substitutes are the ques-
tions of flammability, potential for exposure to the
materials (which can be influenced by the volatility
of the substitute material), and how effective they
are in removing paint. There are also several non-
chemical substitutes,  alternative  methods to
methylene chloride  paint strippers. We need to
consider  the kinds of risks these may present.
   I'd like to review the hazards of methylene
chloride (or dichloromethane). EPA has classified
dlchloromethane as a B2 or "probable" cause of
cancer in humans. The Agency says there is suffi-
cient evidence of carcinogenicity In two  animal
species even though there is inadequate human
evidence. Therefore, the debate continues on the
risks, especially as  related to  differences In the
pharmacoklnetics of dlchloromethane, which ap-
pear to exist between the animals that were used
in the cancer bioassays and the evidence that has
emerged  when human  tissues are used. Exactly
how this will be resolved Is still unknown.
    In addition, dichloromethane can cause other
medical  problems.  Including  liver  toxicity  and
heart, kidney,  and central nervous system
damage.  It Is a volatile material, partially because
consumers and workers encounter high levels of
exposure when using it as a paint stripper.
    I'll now talk about some of the chemical sub-
stitutes for dlchloromethane. Among those com-

pounds EPA identifies as potential high market
share  substitutes for dichloromethane are N-
methyl pyrrolidone,  furfuryl alcohol,  and the
dimethyl ester of a number of dibasic acids—
adipic, glutaric, succinic.
    A major risk consideration, as I mentioned, is
the question of flammability. One of the strongest
factors favoring methylene chloride is that it is
nonflammable. Many of the major market share
substitutes have high or moderate levels of flam-
mability. We believe  this is an  important risk
consideration when evaluating the acceptability of
substitutes—given the likelihood  that  if highly
flammable substances are used in homes and at
the workplace, there's a good chance accidents will
occur. The way the substance is formulated can
reduce its flammability. Reducing the concentra-
tions of the more flammable components may be
a way to  create  nonflammable  formulations.
Another  point is  this: if information on  flam-
mability exists for several of the substitutes, EPA
does not have it.
    Volatility is also another important considera-
tion; it can lead to large differences in the exposure
potential of dichloromethane and the various sub-
stitute materials.  As you  can see,  the relative
volatility expands the range from substantially
lower  than dichloromethane for Af-methyl  pyr-
rolidone to equal to that of dichloromethane in the
case of acetone.  Although we don't have vapor
pressure values for the dibasic esters, given their
molecular weights, we expect them to be substan-
tially less volatile than methylene chloride. But
that information has  not  been developed. The
other aspect of exposure is efficiency. The sub-
stitutes that are less  efficient will require longer
stripping periods and will use more solvent, result-
ing  in higher levels  of  exposure. Therefore, a
material may carry a lower toxic rating than
dichloromethane; if the result from exposure and
use is substantially greater than dichloromethane,
you may or may not be improving the situation.
    Of the major  market share substitutes, only
dichloromethane  is known to be a carcinogen.
Information on the carcinogenicity of virtually all
of the  substitutes is limited. Methylene chloride,
as I've noted, is known  to cause other medical
problems. There are permissible exposure limits
(PELs) and short-term exposure limits (STELs)
available for methylene chloride and some of the
paint stripping substitutes. Several of the sub-
stitute materials, AT-methyl pyrrollidone and the
dibasic esters, do not have PELs at this time—an
example of the limited data available on those
materials. Dichloromethane currently has a PEL
of 500 parts per million, but a proposed revision
in this PEL to 25 parts per million would make it
lower than all the substitutes, except furfuryl al-
cohol, whose PEL is 10 parts per million. There-
fore, toluene, acetone, and methanol could be used
at higher exposure concentrations and not violate
occupational and compliance standards.
    The Office of Toxic Substances has done a
preliminary evaluation of the hazards and poten-
tial risks of the major market share substitutes. In
this evaluation, we combined the data available on
the substitutes and structure activity relation-
ships, basically looking for information on related
materials that may suggest the potential for ad-
verse effects associated with one or more of the
    Potential concerns of one kind or another were
identified for all the substitutes,  including
developmental effects, teratogenicity, neuro-
toxicity, and acute and chronic toxicity. Only fur-
furyl alcohol was identified as  presenting any
possible concern for carcinogenicity.
    Thus we're left with this question: On one side
is dichloromethane, identified by EPA as a prob-
able carcinogen and known to have a variety of
non-cancerous effects. On the other side are the
substitutes—one of which EPA identifies  as a
potential carcinogen. However, there are a number
of non-cancerous effects associated with them.
What that presents is the difficulty in doing the
analysis, in terms of trade-offs between cancerous
and non-cancerous adverse health effects, and
that's a difficult analysis at best.
    It is clear that more information is needed on
the toxicity and exposure potential of the  sub-
stitute materials before we can do a decent assess-
ment of the relative risks. EPA is beginning testing
efforts under TSCA, section 4, on a few of the
substitute materials—JV-methyl pyrrolidone has a
test rule  that we're putting in  place now and
acetone will undergo neurotoxicity testing in the
future.  I should note that industry is voluntarily
conducting tests  on a number of the substitute
materials. An example is Du Font's work on the
dibasic  esters:  it will be conducting bioassays,
attempting to assess the  toxicity of those  sub-
stitute materials.
    Further complicating the analyses of the sub-
stitute materials is that most of them are used as
formulations containing two or more components.
Because of this,  the analyst must consider the
potential hazards and risks of a series of mixtures.
Including possible Interactions among the com*
ponents in the mixtures. These interactions might
increase the dermal penetration of some of the
components, or toxic interactions  might occur
among the materials in the mixtures.

                                                                       Reducing Risk In Paint Stripping
    Because the concentrations of the substitutes
will vary depending on the stripping application.
there is no single, favorable mixture for a given set
of components; however, a series of varying con-
centrations  of the components might yield the
desired stripping properties.   This  makes the
analysis of the potential risks even more compli-
    In the case of N-methyl pyrrolldone (NMP), you
typically encounter materials that contain 15 to 40
percent  NMP.  and, In addition,  find  other
materials. Dichloromethane, itself, is also often
used as a formulation that can have varying
amounts of dlchloromethane and contain, in ad-
dition, toluene, methanol, and acetone.
    A general consideration in  evaluating all of
these substitute  materials is that, in general, the
commercial products of the substitutes don't ap-
pear to perform as well as dichloromethane In
several of the paint stripping applications. Longer
stripping times are required; others are flammable
and will often only remove a limited range  of the
paints and coating materials. This further compli-
cates the task of judging the risks of the sub-
    We have just begun to study the relative risk
potential of the non-chemical technologies, such
as blasting and  abrasives. Several of these non-
chemical alternatives will be discussed in the con-
ference . I encourage attendees when judging those
alternative technologies as well as the chemically-
based  alternatives to consider the relative risks
presented by the different-use scenarios and at-
tempt to compare those risks to dichloromethane
as well as to the  substitutes.
    In  conclusion, when considering  the risks of
the substitutes—once again not the primary focus
of this meeting—we need to consider the full range
of health, safety,  and exposure issues. None of the
high market share  potential substitutes clearly
offers lower risk  potential than dichloromethane,
although several do appear promising. With the
development of  additional understanding  about
the toxicology of these  materials, we may be In a
position to offer more affirmative statements about
the relative safety of some of the substitutes. There
are substantial data gaps in the toxicity and ex-
posure potential of various substitutes; this is a
source of considerable uncertainty.
    Once again,  we need better understanding.
EPA Intends to play a role in Identifying informa-
tion that should  be developed. I would look to our
colleagues in the audience to be mindful  of the
kinds of Information that can be most helpful in
proving that a  given  substitute offers  clearly
demonstrable reductions In risk when compared
to methylene chloride.
    The best prospects at this time appear to be
Af-methyl pyrrolldone and  the dibasic ester for-
mulations as substitutes for methylene chloride.
These  materials are likely to exhibit low flam-
mability and volatility and neither are known or
suspected carcinogens, though  they have been
identified as presenting various non-cancer health
concerns. Substantially more information must be
developed before we can evaluate. In any kind of a
quantitative way. the relative risks presented by
these substitute materials.

Question (Inaudible):
Response: What you are talking about is. In many
ways, the dilemma I face every day in my Job In
offering the kinds of guidance you need. I believe
that EPA should do all that it can  to provide the
information  and understanding that is needed so
that manufacturers can make the right choices
when formulating their products. One thing that
can help us to do that is to have a better under-
standing of those components that are likely to be
included In  paint stripping formulations. If we
understand  those kinds of things early  In the
development cycle, we can work  with industry to
obtain the testing that is needed to understand the
toxiclty and  resultant risks of those materials.
    Unfortunately, It's a fact that toxiclty of most
industrial chemicals is not particularly well char-
acterized, and as soon as you move away from the
relatively small subset of well-studied industrial
chemicals, you often are left with little more than
acute  toxicity information  and perhaps a small
amount of mutagenlclty data, but really nothing in
the way of  any subchronic or  chronic  toxiclty
    To the extent that EPA understands develop-
ing markets, it  can take steps  to see  that the
needed information Is  developed, either through
voluntary initiatives by the chemical industry or
through regulations that would require  testing.
One of the things we're attempting to do, under
Linda Fisher's guidance, is develop a list of those
chemicals that most need data development.

Question (inaudible):
Response: I don't  have any disagreement with
that. In many ways, for certain of these materials,
one could only support the needed testing through
sale of the product; you're not going to spend a
fortune to test something unless you have some
idea of its market acceptability. That's the kind of
thing we deal with all the time at EPA.

    EPA can set up both a push and a pull for test    to develop the information they judge is needed to
data; EPA can, if you will, attempt to pull the data    allow them to make decisions in their best busi-
out of the industry through rules. However, I think    ness interest, to use the safest materials possible
the formulators and users can  also push or en-    that achieve the desired outcome.
courage the producing companies, the suppliers,

U.S.  Federal  Government Activities—Panel
Paul Campanella, Chair
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C.

Sandra Eberle
U.S. Consumer Product Safety Commission
Washington, D.C.

Fayez Hanna
Office of Risk Reduction, Health Standards Division
U.S. Occupational Safety and Health Administration
Washington, D.C.

Robert Rosensteel
Office of Air Quality and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
m Mary Ellen Weber
Dr. Paul Campanella Joined the EPA in 1985 after
spending more than 15 years in  research and
international environmental  work in Latin
America and the United States. Paul was the
senior water analyst in the Office of Management
Systems and Program Evaluation when he first
Joined EPA. He became chief of the Commercial
Chemicals Branch in 1987. Dr.  Campanella will
now introduce the members of his panel.

• Paul Campanella
On this panel, Sandra Eberle represents the Con-
sumer Product Safety Commission, Fayez Hanna
represents OSHA. and Robert Rosensteel is from
the Office of Air.
   Our purpose this morning is to give you back-
ground on how EPA got involved in the solvent
project and some of the things we have done as a
committee to deal with chlorinated solvents. I'm
going to expand the scope of my discussion beyond
methylene chloride because I believe it is impor-
tant to give you a context for what we're doing and
why we're here.
   EPA got involved  in the regulation of
chlorinated solvents in 1985 when the National
Toxicology Program reported a positive result from
a cancer bioassay on methylene chloride. About
the same time, EPA listed methylene chloride as a
hazardous air pollutant under section 112 of the
Clean Air Act. We made a finding, in addition to
that, under section 4(f) of TSCA, that occupational
and ambient air exposures to methylene chloride
may present a significant risk of serious  and
widespread harm to humans.
   hi October 1985, EPA. based on section 4(f),
issued an advance notice of proposed rulemaking
on methylene chloride. At that  point,  federal
regulatory investigation of methylene chloride was
begun by EPA in conjunction with the Consumer
Product Safety Commission, OSHA, and FDA. This
came together as an integrated project because we
were interested in looking at what the other federal
authorities were doing so that we would not dupli-
cate each other's efforts.
    Our focus  was to determine whether
methylene chloride presented a significant risk to
human health or to the environment, to determine
if regulatory actions were necessary, and what
agencies would be best able to take those actions.

The Initial scope of the Chlorinated Solvents Coor-
dination  Committee was to study possible sub-
stitutes for methylene chloride, and in 1985 those
included  trichloroethylene, perchloroethylene,
1,1,1-trichloroethane, carbon tetrachloride, and
CFC 113.
    In  the beginning,  we focused  on the use
categories presenting the greatest risk potential:
dry cleaning, solvent cleaning (focusing primarily
on electronics and metal cleaning), aerosol uses,
and paint stripping. We took an integrated ap-
proach to determine which statutory authorities
were best qualified for controlling risks. Obviously
there was a lot of interest at the Consumer Product
Safety Commission under the Federal Hazardous
Substances Act; at OSHA because of the Occupa-
tional  Safety and Health Act; at FDA because of
the Federal  Food, Drug, and Cosmetic Act; and
EPA's  authority came under both the Clean Air
and the Toxic Substances Control acts.
    When the study began, there were permissible
exposure limits (OSHA PELs) on dichloromethane
of 500 parts per million for an  eight-hour, time-
weighted average. There was also a PEL on
trichloroethylene  of 100 parts per million and on
perchloroethylene of 100 parts per million. The two
solvents  carbon tetrachoride and CFC 113 were
withdrawn almost immediately from analysis be-
cause, at that point, CFC 113 was already under
consideration for regulation by the Office of Air and
Radiation as an ozone depleter; I think that rule
became  final in  August  1988. 1,1.1-trichloro-
ethane remained part of the analysis initially but
has since been removed because it is being regu-
lated as an ozone depleter under the terms of the
Montreal Protocol and Title Six of the Clean Air Act.
Both of those chemicals will be  phased out of
commerce by the year 2002.
    The work group conducted numerous evalua-
tions—mainly hazard, exposure, and risk evalua-
tions—of the very few  standards; we developed
exposure scenarios, analyzed those scenarios, did
some economic analysis, and came up with risk
management strategies for each  use category. The
work group did not attempt to reconcile differences
in the statutory directions; instead, we chose from
among the various options those we thought would
best reduce risks, and when we  reached that sort
of a determination, we decided what agency would
be the  most appropriate  to take  action.
    That brings us to the present. I will now turn
the discussion over to my colleagues on the panel
and ask them to briefly describe and bring us up
to date on the actions  taken in their respective
organizations regarding methylene chloride.
    In June of 1989, FDA put into effect a regula-
tion under the Federal Food, Drug, and Cosmetic
Act that prohibits methylene chloride—called "a
significant cancer risk to consumers"— as an In-
gredient in cosmetics. FDA noted that "any cos-
metic product that contains methylene chloride as
an ingredient is deemed adulterated and subject
to regulatory action." That was the only action FDA
has taken on chlorinated solvents.

• Sandra Eberle
I will just briefly try to put CPSC's role in context
for you. As Paul outlined, we have benefited from
interagency attempts to coordinate actions to as-
certain that the best approaches are  taken for
these chemicals and their potential uses and to
make sure the federal government was being effec-
tive and responsible in the use of resources. CPSC
has benefited from EPA's knowledge; I think that
the exchange between both agencies and certainly
with OSHA and FDA has been very worthwhile.
and an example we will follow in many future
    CPSC's interest in paint strippers has been
from the consumer product's side and, for
methylene chloride and the other chlorinated sol-
vents, date from before the commission's earliest
days. These  chemicals are regulated  under a
statute that pre-dates  the agency,  called the
Federal Hazardous  Substances Act, which puts
the burden on the manufacturer to properly label
any hazardous product introduced for use in and
around  households.  We  were  aware that
methylene chloride  in a paint stripping  product
presented a hazard because it always had caution-
ary labeling, mainly  for other  ingredients like
methanol, which is highly toxic and requires a
skull and crossbones. Therefore, CPSC's interest
in products that contain methylene chlorine was
long-standing, whether  they were aerosols, car-
buretor cleaners, or paint strippers (which certain-
ly have the heaviest methylene chloride use and
    In working together  as a federal community,
we  were able to identify various exposure areas
and determine what CPSC was doing to regulate
aerosols or paint  strippers containing these
chemicals. (Carbon tetrachloride had been banned
for  consumer use for a considerable number of
years;  the others had other labeling issues as-
sociated with them.) CPSC issued a statement of
policy that made it clear these data were sufficient
to trigger new labeling for products that contained
significant amounts of methylene  chloride—
amounts that could present a serious risk of per-
sonal injury or illness.

                                                                      Reducing Risk In Paint Stripping
   Our first step was to institute basic statutory
requirements on the labeling for these products.
Information had to be added about the  new
dangers associated with the use of paint strippers
containing methylene chloride. This requirement
for labeling all hazards, chronic or acute, has
always been a part of the Federal Hazardous Sub-
stances Act; however, information about chronic
hazards is not as advanced as data on certain
acute hazards, such as acute toxicity.
   By next year, CPSC will have completed an
evaluation of methylene chloride in paint strippers
and other consumer products. We  have already
compiled a list of product manufacturers under
our jurisdiction who use methylene chloride In
consumer products. CPSC will also conduct a
consumer survey to get updated Information on
how people use these products and how aware
they are of the labeling. The new instructions for
use have  been publicized through a variety of
electronic  and print  media as well as speeches to
community action groups.
   This survey will help us to update risk assess-
ments on methylene chloride, after which commis-
sioners will decide whether any additional actions
are needed. These actions could range from some
type of product standard that limits exposure all
the way to a  ban on the use of the chemical.
Obviously, the kind of information we are exchang-
ing at this conference about substitutes for the
consumer market and  additional  options  that
might be taken, such as product stewardship, Is
Important to these considerations.

• Fayez Hanna
OSHA will be developing a standard for controlling
worker exposure to  methylene chloride that will
apply to every industrial segment, not just paint
strippers.  We plant  to conduct risk assessments
on toxic and carcinogenic effects and then evaluate
the technological feasibility of achieving a certain
level.  Our draft proposal has been approved for
publication In  the Federal Register by  the the
Office of Management and Budget,  pending con-
sultation with the Advisory Committee for Con-
struction,  Safety, and Health.
   Technological feasibility  is the nucleus  of
OSHA's standards. I'm In favor of using engineer-
ing controls in some situations where we don't
have  sufficient Information  on toxicity or car-
clnogenlclty. Most people think engineering con-
trols and technological feasibility are limited to a
fan. exhaust system, or blower; in actuality, there
are several components that present many ap-
proaches to solving engineering problems. Another
element OSHA considers is the cost of those con-
trols. We have developed a standard that covers
the various aspects of controlling exposure and
reducing risks without causing undue economic
hardship on industry.
• Robert Rosensteel
I will provide an overview of Title 3 of the recently
enacted Clean Air Amendments  that  won't  be
directed at methylene chloride,  specifically,  as
much as our overall Title 3 activities. Keep In mind
how Title 3 might affect sources you're interested
in, especially paint stripping and other processes
that may be emitting any one of the 189 hazardous
air pollutants on the Title 3 list. Methylene chloride
is one of the pollutants in the list of 189.
    A process is being developed that will allow the
public to petition to add or delete pollutants from
that list. EPA must make a determination within
18 months after It receives a petition. We are also
required to publish a list of the major source
categories emitting one or more of these 189 haz-
ardous air pollutants. A major source Is defined as
"one that emits 10 tons per year or greater of an
individual pollutant on the list or 25 tons per year
or greater of multiple  pollutants If the  source Is
emitting more than one and that source is also
defined as a contiguous area under common con-
trol." We are required to review and revise this list
at least once every eight years. In addition,  we
must publish an emissions standards schedule for
each of the source categories on this list. We plan
to publish a draft list in May 1991  and allow a
short, 30-day period for comments from the public
about listed source categories. This list will be
made final on November 15, 1991.
    We can't tell you when a maximum achievable
control technology (MACT) regulation  emission
standard will be established because we haven't
developed Schedule I. In doing so, we will consider
adverse effects on public health and the environ-
ment, the quantity and location of  the category
emissions, and the efficiency gained by grouping
categories according to pollutants, processes, or
technologies. Having done that, we are required by
the amendments to promulgate regulations over a
period of 10 years.
    The initial requirement we're working on is to
promulgate emissions for 41 source  categories or
subcategories within two years of enactment
(November 1992). By the four-year mark, we must
develop emissions standards for 25 percent of the
listed categories; by the seven-year mark, 50 per-
cent of the categories; and In  10 years, emissions

standards for 100 percent of the categories on the
published list as of November 1991.
    MACT requires development of emissions
standards that would achieve the maximum emis-
sion reduction deemed achievable by EPA for new
and existing sources In the category. The new twist
to this authority Is the minimum control level, or
as we have been calling It within the program, the
"floor" for new sources. A  new source must be
controlled at a level at least as stringent as the
best-controlled similar source that is the "best of
the best." There also is a minimum  control floor
for  existing sources, which  requires  that they be
controlled at a level at least as stringent as the
average of the best 12 percent in the  source
    EPA's administrator then has  discretion to
consider emission standards that are more strin-
gent than these  floors, and,  In doing so, may
distinguish among classes, types, and sizes of
sources within a category to determine how strin-
gent those rules should be. There are general
MACT emissions standards  that are  currently
being developed.
    One  rule  will affect the  synthetic organic
chemical manufacturing Industry's relatively high
volume petrochemical processes. If you  are
manufacturing what I call a "sock me" chemical
and using an organic pollutant on the list of 189,
then you are affected by this rule. There tends to
be confusion about this: the rule pertains to the
manufacture of a chemical, not the use of a chemi-
cal. The production of methylene chloride will be
affected by this rule; however, the use of methylene
chloride in paint stripping would not. We're also
working on a comprehensive revision to asbestos
rules  and standards for chromium electroplating
and commercial sterilizers.
    In addition,  we are assessing petroleum
refineries and manufacturers of iron and steel and
wood  furniture. Pulp and paper mills are being
studied by numerous offices within EPA, which are
cooperating to produce new regulations.
    The MACT compliance schedule  normally re-
quires that, once a rule has been promulgated EPA
has up to three years to bring the sources  Into
compliance. There is a provision for one-year ex-
tensions either by EPA or the state. If it has an
approved permanent program. Another provision
is early reduction; if a company achieves 90 per-
cent early source reduction, then It gets a six-year
extension from the MACT promulgation date. It
can also get an extension of five years to comply
with the MACT regulation If it has Installed best
available control technology before the  rule goes
Into effect.
   After having applied these MACT rules. EPA
must consider residual risks. After we promulgate
the standards, then we determine If there Is an
ample margin of safety to protect public health or
prevent adverse environmental effects. For pol-
lutants classified as "known," "probable," or "pos-
sible"  human carcinogens, if the maximum
exposed individual has more than a one-in-a-mll-
lion  risk, then we are required to  set a more
stringent emissions standard for that  source
category within eight years of the development of
the MACT regulation, and for the two-year stand-
ards, within nine years.
   One other provision concerns modification.
Companies are modified if they Increase emissions
of hazardous air pollutants or have started using
a hazardous air pollutant and are emitting it. In
this case, if a company has  reduced a more toxic
pollutant  on the list of 189, you can offset the
increase in emissions of the less toxic one.

Question: What does NESHAP stand for, and why
are surface coatings at the bottom of the list?
Bob  Rosensteel:  NESHAP stands for National
Emissions Standards for  Hazardous Air Pol-
lutants. The list Is in no particular order; those are
all active projects.

Question: I believe consumer education is the key
to success for the whole solvent replacement pro-
gram. With regard to the consumer paint stripping
applications and the new warning on the label
associated with the use of methylene chloride, I'd
like to know If EPA has taken a survey to determine
whether the consumer reads the warning on the
label. If customers do read the label, how much do
they understand about methylene chloride, and if
they don't, what is EPA doing in conjunction with
OSHA to educate the consumer?
Sandra Eberle: The consumer-use applications of
methylene chloride and the consumer education
programs to encourage safer use of any products
that contain it are the responsibility of the CPSC.
CPSC, in cooperation with the Industry, has been
actively advising the public  of steps to take, both
encouraging people to read the label and using
other means to get out additional information.
   In addition, we have a survey at OMB that will
ask  consumers if they read the label  and then
measure their understanding of it. To some degree,
we should be able to elicit whether or not they
understand the hazard  and are taking the  risk
anyway or are  not informed and therefore  not
acting to reduce the risk.

OECD Activities  Overview—Panel
Mary Ellen Weber, Moderator*
Office of Toxic Substances
U.S. Environmental Protection Agency
The Canadian Approach to Regulating Paint Strippers
George Long
Department of National Health and Welfare
Ottawa, Canada
n Canada, paint strippers are assessed both
as consumer products and Industrial
Consumer Products

Chemicals contained in them are mainly governed
under Schedule I of the Hazardous Products Act,
which Is administered by Consumer and Cor-
porate Affairs Canada (CCAC), with the Depart-
ment of National Health and Welfare providing
advice in matters of human health.
   Under the Hazardous Products Act, dangerous
chemical products may be controlled in several
   • An outright ban,
   • Regulations imposing safety requirements,
   • Requirements for special packaging, such
     as child-resistant closures, and
   • Precautionary labeling and adequate
     directions for use.

   Regulations pertaining to paint removers are
found in the Consumer Chemicals and Containers
Regulations of the Act, which govern their adver-
tising,  sale, and importation.  To be  regulated
under the Act, a paint remover must  contain
specific concentrations of named chemicals.
   Depending upon the product formulation, the
Regulations specify precautionary labeling, which
Includes a hazard symbol, a hazard statement.
and first aid statements. Precautionary labeling is
required for paint removers containing specified
amounts of such regulated chemicals as methanol
or toluene. However, methylene chloride is not
regulated under Schedule I of the  Hazardous
Products Act.
   In 1985, Consumer and Corporate Affairs
Canada released an information bulletin—"Health
Hazard Posed by Paint Strippers and Spray
Paints"—in response to public concern over:
   • Reports that methylene chloride proved
     carcinogenic to laboratory animals, and

   • The increased risk of methylene chloride
     exposure for people with circulatory
     problems or heart conditions.

In the information bulletin, CCAC advised con-
sumers to use paint strippers in a well-ventilated
   In 1988. concern over paint strippers contain-
ing methylene chloride prompted CCAC and the
Department of National Health and Welfare to
initiate a review of this issue.
   With the Department of National Health and
Welfare providing advice on the potential human
health effects of acute and chronic exposure to
methylene chloride, CCAC examined the issue in
terms of costs and benefits. CCAC also considered
the question of alternatives to methylene chloride-
containing  paint strippers, including sanding,
heat-stripping, and professional stripping, along
with attendant problems such as volatilization of
   Concurrently. CCAC initiated a major review
of its regulatory system for consumer chemicals
 •Bo Wahlstrdm, Chair, National Chemicals Inspectorate, Sweden, was unable to attend due to the Persian Gulf situation.

and decided to move from an ad hoc system to one
that is criteria-based. As a result, no decision on
the regulation of methylene chloride will be made
until the new system is in place.
   Presently,  consumers  are  advised to use
methylene chloride-containing paint strippers in a
well-ventilated area, defined as "one in which the
odour of the chemical cannot be detected."
Industrial Products

The Hazardous  Products Act has provisions for
industrial products under Schedule II. In Canada,
paint strippers used in occupational settings are
subject to the Controlled Products Regulations. In
addition, the Workplace Hazardous Materials In-
formation System (WHMIS) was established under
a combination of federal and  provincial laws. The
legislative bases to enable its implementation are
the Hazardous Products Act, the Canada Labour
Code, the  Hazardous  Materials Information
Review Act,  and provincial occupational health
and safety acts.
    WHMIS  provides Canadian  workers  with
uniform  safety information about chemical
products in the workplace. The system's three key
elements are:
      1. Labels, with symbols, on hazardous
       material containers.
     2. Material safety data sheets, and
     3. Worker education programs.

    Products are  classified by  a  criteria-driven
system. If a product meets the criteria as a con-
trolled product, all hazardous ingredients must be
disclosed unless an exemption is granted through
a provision for product trade secrets. Methylene
chloride is on the Ingredient Disclosure List, which
means that it must be identified on the material
safety data sheet of a controlled product if It Is
present in a  concentration of 0.1 percent or
    Under the WHMIS criteria, both the acute and
chronic effects of a chemical must be declared.
Methylene chloride, classified as an acutely toxic
substance, also meets the crltiera as a potential
carcinogen because it is classified by the Interna-
tional Agency for Research on Cancer as a Group
2B carcinogen.

Canadian Centre for Occupational Health and Safety.
    1990. CHEMINFO. Record Number 76E: Methylene
Commission de la sant£ et de la se'curttd du travail du
    Quebec.  1990. Information Toxlcologlcal Index:
    Methylene Chloride.
Consumer and Corporate Affairs Canada.  1985. Infor-
    mation. Health Hazard Posed by Paint Strippers and
    Spray Paints. CCA-1484 (06-83). Ottawa.
Health and Welfare  Canada.  1987. Environmental
    Health Directorate. Health  Protection  Branch, Ot-
International Agency  for Research on Cancer. 1987.
    IARC Monographs on  the Evaluation of Car-
    cinogenic Risks to Humans. Overall Evaluations of
    Carcinogenicity: An Updating of IARC Monographs,
    Volumes 1 to 42. Supplement 7. Lyon, France.
O'Reilly. J. 1989. Complying With WHMIS: The U.S.
    Manufacturer's Guide to Canada's Chemical Label-
    ing Regulations. Roytech Publications. Inc.. Burlln-
    game, CA.
Workers' Compensation Board of British Columbia.
    1988. WHMIS Core Material. A Resource Manual for
    the  Application and Implementation of WHMIS.
    Richmond. BC.

OECD Activities  Overview—Panel  (continued)
Regulation ofMethylene Chloride in  the
United Kingdom
Bill Holmes
Health and Safety Executive
Technology Division
Bootle, Merseyslde, United Kingdom
Regulation of Hazardous
Substances in the United

The United Kingdom Health and Safety Commis-
sion (HSC) and Health and Safety Executive (HSE)
are bodies created by the Health and Safety at
Work Act of 1974. The HSC is responsible for the
administration of the act. In particular, its duties
include taking appropriate steps to secure the
health, safety, and welfare of persons at work and
to protect the public against risks to health and
safety arising out of work activities. The commis-
sion also commissions  and sponsors research,
promotes training, and  provides an information
and advisory service. The HSC is made up of eight
representatives of trade unions, employers, and
local authorities, and a ninth member appointed
by the Secretary of State for Employment to rep-
resent wider consumer and public Interests. A
full-time chairman is appointed by the Secretary
of State.
    The HSE is responsible for day-to-day enforce-
ment of health and safety legislation and contains
divisions dealing with policy. Inspection, scientific,
medical, and technical activities. The legislation
dealing with exposure to toxic chemicals In the
United Kingdom is the Control of Substances Haz-
ardous to Health Regulations 1988 (COSHH). This
law is a comprehensive  set of regulations requir-
ing, among other things, that employers assess the
risks to health arising from work with hazardous
substances and apply  appropriate control
measures. A hierarchy of controls includes
elimination, substitution, enclosure, local exhaust
ventilation, systems of work, maintenance, and
general ventilation monitoring.
   In setting standards  for hazardous sub-
stances, the Health and Safety Commission makes
substantial use of the  Advisory  Committee  on
Toxic Substances (ACTS). This committee com-
prises persons nominated by industry and trade
unions, together with independent experts. ACTS
is  advised on occupational exposure limits  for
particular substances by the Working Group for
the Assessment of Toxic Chemicals (WATCH), a
tripartite group of experts. Data on the toxicity,
production, uses, exposure, control, and sampling
of Individual substances are  collected and
analyzed  by HSE staff for WATCH to review.
WATCH then makes appropriate recommenda-
tions to ACTS. Wide consultation Is carried out on
the proposals before the limits are subsequently
incorporated into the legislation.
   Two types of occupational exposure limit (OEL)
can be established under the COSHH regulations:
occupational exposure standard (OES) and maxi-
mum exposure limit (MEL).
   An OES is proposed if: (1) a "no effect level" for
repeated exposure can be identified; (2) exposure
to concentrations greater than the OES for the
time it might take to identify and remedy the cause
of the excessive exposure is unlikely to produce
short- or long-term serious effects; and (3) the OES
can reasonably be complied with.
   A MEL Is proposed If: (1) a substance Is not
able to satisfy the OES criteria and Is liable to pose

a serious risk to humans (acute toxlcity and/or
potential to cause serious  long-term health ef-
fects); or (2) socloeconomlc  factors Indicate that,
although the substance meets the criteria for an
OES, a  numerically higher  value Is necessary If
certain uses are to be reasonably practicable.
    Where a substance has an OES, compliance Is
achieved if exposure by inhalation Is controlled to
the specified level, or, where the OES Is exceeded,
the employer identifies the reasons and takes ap-
propriate remedial action as soon as is reasonably
    If a MEL has been established fora substance,
exposure must be reduced to a level as low as
reasonably practicable  and must not exceed the
Policy Regarding Methylene

Methylene chloride is currently assigned a MEL of
100 ppm (8-hour time weighted average). The
United Kingdom considers that exposure at this
level Is unlikely to produce harmful effects on man.
The substance Is assigned a MEL In view  of the
rapid increase in central nervous system effects
with greater concentrations and the potentially
serious consequences where exposure might ex-
ceed a few hundred ppm pending implementation
of Improved control measures.
    In the European Community (EC), a Directive
has recently classified methylene chloride as a
category 3 carcinogen (i.e.,  possible irreversible
effects)  with consequent additional labeling re-
quirements. The United Kingdom did not support
the proposal but will,  of course. Implement the
    ACTS/WATCH reviewed all available data and
concluded that, although the risk of carcinogenic
effects could not be entirely discounted, the car-
cinogenic effects observed In animal studies ap-
pear to be of doubtful relevance to humans. In
particular, major studies  carried out  by the
European Chemical Industry Ecology and Toxicol-
ogy Centre (ECETOC) highlighted the different
metabolism of methylene  chloride  In  animal
species. It  was on this basis that the United
Kingdom opposed the EC proposal for classifica-
tion as a Category 3 carcinogen.
   Methylene chloride Is a very effective paint
stripper that HSE believes to be controllable and
relatively safe for  the environment. Replacement
with substances about which there is Insufficient
Information and which may Introduce other risks
is questionable. The HSE view is that hazards and
risks should be closely evaluated and a decision
based on relative risk assessments.
   The main  industrial  problem Involving
methylene chloride In the United Kingdom is fur-
niture stripping, which Is usually carried out in
small premises with few  employees. High ex-
posures have been found in this sector and have
proved  difficult to control. HSE believes  that
properly designed, installed, and maintained con-
trol equipment, suitable work systems, and good
housekeeping are  key factors in solving the prob-
lem. A Specialist Inspector Report on paint strip-
ping to provide details on  exposure levels and
practical control measures  is being prepared by
the Occupational Hygiene Unit  of HSE's Technol-
ogy Division. This publication will be available to
the public without charge.
   The United Kingdom's view on methylene
chloride evolved from a broad base of science and
experience and is  endorsed  by independent com-
mittees, toxlcological experts, and academics. Our
system is "open"  and receives  great cooperation
from all sectors of Industry. We believe that the
HSE position should receive serious consideration
from other countries facing the trade-offs Involved
In making sensitive decisions regarding the
regulation of chemicals and the environment.

OECD Activities Overview—Panel  (continued)
OECD Risk Reduction Activities:
A Process for Cooperative Work on Specific  Chemicals
Victor Morgenroth
Organization for Economic Cooperation and Development
Parts, France
    In March 1990. the Organization for Economic
    Cooperation and Development (OECD) held
    an ad hoc meeting of experts in Stockholm to
explore a new approach to managing chemicals.
This meeting discussed the so-called "sunset" in-
itiative, whereby the use of chemicals with risks
considered incompatible with sustainable
development would be phased out either totally or
for certain uses as safer acceptable alternatives
become available, and recommended that it be
included within the wider concept of risk reduc-
   To incorporate the sunset initiative, measured
responses to deal with unacceptable risks must be
developed through application of various instru-
ments appropriate to both the nature and extent
of the risk. These responses  would encompass
both regulatory and nonregulatory measures as
well as economic instruments and could include:

    • Cleaner products and technologies.

    • Emission inventories.

    • Labeling.

    • Citizen and consumer guides.

    • Training materials,

    • Product Stewardship commitments,

    • Recommended disposal or recycling

    • Use limitations, and

    • Phaseout or banning of chemicals for
     certain, specific uses.
Risk Reduction of Specific

At their 14th joint meeting, the Chemicals Group
and Management Committee of the OECD Special
Programme on the Control of Chemicals agreed
that new risk reduction activities should be started
with a pilot project on the risk reduction of specific
chemicals. A lead country approach within the
framework of the cooperative work on existing
chemicals was chosen as the most appropriate way
to initiate this work.
   The lead countries that agreed to be respon-
sible for specific chemicals were:

   • The Commission of the European
     Communities (for cadmium, Sweden as

   • The United States (for lead, Denmark as

   • The Nordic countries (for mercury),

   • The Netherlands (for brominated flame
     retardants), and

   • Sweden (for methylene chloride,
     Switzerland as co-sponsor).

 Preparation of Analyses of Risk
 Reduction Possibilities

 Each lead country has prepared a draft analysis of
 the possibilities for risk reduction that includes:

    • A rationale for initiating the study.

    • A brief summary of current hazard and/or
     risk assessments. (It is well documented
     that certain of the selected chemicals.
     mercury, lead, cadmium, and methylene
     chloride are potentially harmful to health
     and/or the environment. These
     compounds as well as brominated flame
     retardants have been or are being
     reviewed by the United Nations
     International Programme on Chemical
     Safety,  which has prepared
     comprehensive, peer-reviewed hazard

    • An analysis of the various uses, sources.
     pathways, and environmental fate of the
     chemical(s), including commercial and
     environment life cycles and mass flow

    • Possibilities for. or estimates of, exposure
     from  each of the significant uses.

    • Identification of the extent or degree to
     which certain uses are essential.

    • The availability of substitutes (chemicals
     and/or technologies) in the foreseeable

    * Suggestions for regulatory, nonregulatory.
     and economic instruments to achieve
     meaningful risk reductions.

    • Possible strategies for risk reduction at
     both  the national and, as appropriate, the
     international level.

    Other member countries assisted the lead and
co-sponsor countries by submitting information
on the  selected chemicals that included

    • Summaries of new data on the hazards or
     risks of the chemical:

    • Information on use categories, production
     volumes, and

    • Environmental and/or commercial life
     cycles;  possible substitutes and/or
     control technologies, and existing or
     planned regulations  or risk-reduction

    In  November 1990.  the lead countries sub-
mitted  the first drafts of executive summaries and
analyses to the other member countries. The Joint
Meeting determined that these documents were of
value and  that, once finalized, should be con-
sidered for derestrlction  to make them widely
available. It also agreed that draft  reports should
be broadened,  peer-reviewed,  and  finalized
through a value-added commenting process, open
to all member countries and all sections involved,
that would lead to consensus building, improve
the consistency, and ensure high quality results.
Member countries using or considering different
approaches to risk reduction  of the five subject
chemicals or groups of chemicals than those al-
ready discussed or covered in the  reports  will
describe their experiences.

Consultation Process

Early comments have emphasized  the  need for
including an  analysis of the economic effects of
certain suggested risk reduction measures; more
extensive consideration of the need  for  and
availability of substitutions—particularly where a
phasing out is suggested (including commentary
on the adequacy of substitute assignments; and a
crlsper presentation of certain aspects of risk as-
sessment that lead to specific suggestions for risk
   Once the comments of member countries have
been  incorporated, the documents will be con-
sidered for derestriction as discussion documents
so that all sectors including labor, industry, and
various nongovernmental organizations can have
an opportunity to comment on the substance and
the recommendations  included In  the reports.
Subsequent to that consensus-building process,
they will be considered for publication as  OECD
documents. This process should be completed by
the end of 1991  or sometime  in early 1992. The
final  reports would  also  serve as  a  basis for
decisions on the future direction of risk-reduction
 The New OECD Council Act on
 Existing Chemicals

 As work began on-risk reductions of specific
 chemicals,  the Joint Meeting  endorsed a more
 general policy statement. This was Incorporated In
 an OECD Council Act on the Co-operative Inves-
 tigation and Risk Reduction of Existing Chemicals.
 which  was considered by environment ministers
 and adopted by the Council In January 1991. The
 ministers discussed risk reduction as a general
 policy issue and the opportunity to make a com-
 mitment to risk reduction on a cooperative basis.
    It should be emphasized that the pilot project
 on risk reduction was not advanced enough for
 ministerial decisions on specific chemicals.

Labor's  View on  Reducing  Risk in
Paint Stripping
John B. Moran
Occupational Safety & Health
Laborers' Health and Safety Fund of North America
Washington, D.C.
       This conference is unique in three impor-
       tant and significant aspects. First, most of
       the use areas involve one common recep-
tor: workers. Second, the conference's topics are
all on well-recognized, basic industrial hygiene
approaches to  reducing exposures to workers.
Third, and most importantly, with the sole excep-
tion of this presentation, labor is not represented.
Frequently, labor's role as a stakeholder has not
been recognized in meetings such as this con-
ference. Perhaps this occurs because some busi-
nesses think that labor either cannot or should not
participate. Another aspect of this conference
should be recognized: the sponsor Is the U.S.
Environmental Protection Agency (EPA), while the
responsibility for worker protection rests with the
Occupational Safety and Health Administration.
   It is heartening to see EPA becoming—through
the Toxic Substances Control and Resource Con-
servation and Recovery acts and other legislative
mandates—more actively involved in areas Impor-
tant to worker protection. During the past months.
EPA has embraced labor as a stakeholder in these
matters by creating the special task force to focus
on worker protection issues at Superfund sites,
inviting active labor participation In the HUD/EPA
lead-based paint task force, and appointing one
labor representative to the 27-member, negotiated
rulemaking panel for lead-acid battery recycling
   We are encouraged and commend EPA for
expanding Its horizons on these Important Issues
to Include those most directly  Impacted:  the
workers. We can, have, and will seek to continue
to be Informed contributors.
   Labor is an Important constituency that Is
directly impacted In every step of the Toxic Sub-
stances Control Act cradle-to-grave route. Since
workers are—all too often—the first and worst
exposed, our contributions can be Important to
overall national efforts to reduce or  eliminate
human risk associated with exposure to hazard-
ous materials or substances.

Product  Stewardship—Panel
Paul Cammer, Chair
Halogenated Solvents Industry Alliance
Product Stewardship and Chemaware at Dow
William C. Hayes
Chemicals & Metals Department
Dow Chemical Company
Midland, Michigan
       Today I will briefly describe Dow's product
       stewardship program, and then provide
       some specific examples of Dow's product
stewardship efforts In the area of paint stripping.
   At Dow, we believe that product stewardship
Is  an Investment In the future.   In fact,
stewardship and concern for the environment are
part of the company's core values. Our product
stewardship philosophy Includes obtaining and
assessing health and environmental information;
evaluating customer use; and taking appropriate
steps to protect employees, the public health, and
the environment. In short, we have made a com-
mitment to do what's right.
   The program has five purposes:

   • Protect employees, the public health, and
     the environment;

   • Protect our products from the

   • Help reduce liability;

   • Help prevent adverse publicity; and
   • Increase customer involvement and

   Dow's product stewardship program Is not
new; it began more than 60 years ago. Examples
of Dow's product stewardship activities follow:

   • 1930—First monitored plant effluent.

   • 1933—Established toxicology laboratory.

   • 1946—Opened first rotary kiln for wastes.

   • 1950—Conducted first industrial hygiene
     survey for customers.
   • 1958—Developed first material safety data
   • 1969—Formed corporate ecology council.

   • 1972—Formally defined product

   • 1977—Held first product stewardship
   • 1987—Launched Chemaware program.

   The responsibility for product stewardship is
not confined to any one  person or group. The
responsibility for product stewardship Is shared by
many company functions, including Research and
Development, Manufacturing, Distribution, and
Marketing. The Research and Development func-
tion obtains data, develops acceptable  applica-
tions, and provides Information. Manufacturing
informs employees, assures a healthy work en-
vironment, and adheres to pollution control and
industrial hygiene standards and guidelines. Dis-
tribution selects carriers, warehouses,  and ter-
minals to perform according to Dow's guidelines.
And  Marketing furnishes customers and dis-
tributors with appropriate information, informing
them about known use limitations.
   The product steward for a specific product or
chemical  is typically In  Technical  Service and
Development (TS&D). The functions of the product
steward Include assessing appropriate uses of the
product or chemical, assisting sales personnel,
evaluating customer use and disposal practices,
preparing training  tools, recommending needed
health and environmental studies, and interacting
with governmental agencies.

    In response to a need for greater, more visible
product  stewardship,  we  have developed
Chemaware .* Chemaware is the Chemicals and
Metals Department's enhanced product and en-
vironmental stewardship program designed to as-
sist users of our products with handling, storage,
recycling, disposal, and safety procedures. The
Chemaware stewardship program:

    • Increases awareness of proper

    • Documents product stewardship efforts;

    • Minimizes product liability;

    • Reduces need for additional regulation;

    • Places the company in a leadership role
      for product stewardship.

    Elements of our Chemaware program that are
available to our distributors and customers in-
clude services designed specifically for chlorinated

    • Training aids and videos;

    • A product stewardship manual;

    • Technical literature; and

    • Distributor training and  environmental
Additional services that are available at the discre-
tion of TS&D Include:

    • Field support;

    • Laboratory and analytical support;

    • Vapor monitoring;

    • Environmental and regulatory services;

    • Solvent conservation and emissions

    There are materials and services available for
methylene chloride  and, more  specifically, for
paint stripping.  Our basic materials include the
solvent stewardship manual, a Chemaware kit for
methylene chloride, and a videotape  on how to
handle  methylene chloride  safely.  The video is
available for viewing through Dow Field Sales and
    Our efforts in paint stripping are obviously
more  focused. For example, at the  Halogenated
Solvents Industry Alliance, we  created a polnt-of-
purchase brochure on the safe way to strip paint
from wood.  More than 100.000 copies of this
brochure have been sent to distributors and for-
mulators for further distribution to the customers.
In addition, over 65,000 copies  have  been dis-
tributed by the Consumer Information Center In
Pueblo, Colorado.
    In  1990. we also  developed a  short feature
article on the safe use of methylene chloride. The
article  was distributed to over 7,000  suburban
newspapers with a projected circulation  of 23
million readers. Throughout 1989, a radio public
service announcement was aired on  265 radio
stations reaching an estimated 15 million listeners
in 46 states. A similar project Is planned for this
year. We also  are working  with the producer of
public  television's This Old House" to include a
segment on paint stripping In 1991. Our goal is to
have safe handling Information included on any
program that  involves the  use of methylene
chloride paint  strippers. For the Industrial paint
stripping segment, we plan to  develop a safe han-
dling video In 1991.
    Finally, we have placed articles on the safe use
of methylene chloride paint  strippers In Industry-
specific journals. Articles published since 1988
    • 1988. Methylene chloride: balancing
     health with safe handling. American Paint
     & Coatings Journal.

    • 1988. Safe handling urged with methylene
     chloride. American Painting Contractor.

    • 1989. Safe use of methylene chloride.
     Occupational Hazards.

    • 1989. Methylene chloride for furniture
     stripping: effective and safe if handled
     with care. American Painting Contractor.

    • 1991. Methylene chloride paint strippers.
     Old-House Journal.
We will continue to seek opportunities to educate
the public and the worker.

    In closing.  Dow has a three-part commitment
to product stewardship:

    • To ensure the safe manufacture.
     distribution, and use  of Dow products;

    • To do what we know is right; and

    • To provide this information and service to
     help our customers do the same.

Product Stewardship—Panel  (continued)
Controlling Paint Stripping Emissions
W. Piatkiewicz
ICI Chemicals and Polymers
Runcorn, Cheshire, United Kingdom
    Ideally, a paint stripper should be effective in
    formulations  with all paint types, have an
    acceptable toxicological profile, and be an
environmentally safe product. However, no matter
how well they fulfill these goals, all paint strippers
produce emissions in the workplace.
    Four approaches should be taken to reduce
these emissions:
    • Change the formulations

    • Install more-suitable equipment

    • Use better working practices and
    • Provide adequate ventilation.


The following  table shows the effect of different
formulations on emissions.

Table 1.—Effect of formulation on emissions.

Formulation "A"
Formulation "B"
Formulation "C"
Formulation "D"
Formulation "E"
70 sees.
5 min. 50 sees.
5 min.
4 min. 40 sees.
4 min. 30 sees.
3 min. 20 sees.


 A good solution for controlling emissions is to
 capture the vapors at the source. When stripping
 paint, this can be done by using a lid or a perimeter
 slot around the rim of one side of the tank (or
 storage vessel), and a corresponding air input slot
on the opposite side of the tank, preferably along
the major axis. Figure 1 depicts a paint stripper
bath with a manual rolling shutter lid; Figure 2
gives an idea of the proportions of a paint stripper
tank that is equipped with both a lid and rim
   These recommendations are derived from the
metal cleaning industry's use of chlorinated sol-
vents and have been shown to effectively achieve
compliance to occupational exposure limits. It is
only sensible to extend  these practices to paint
Working Practices

Employees can reduce emissions by using better
handling practices.
    The rate of removal of material from a stripping
bath should be a maximum of 10 feet per minute
with a vertical lift. During 2,000 annual working
hours, drag-out, idling (idling plant set for opera-
tion), and standing (plant not operating, lid off
tank) losses of emissions each usually total 30
percent; clean- out losses encompass the remain-
ing 10 percent. However, because drag-out losses
depend on the amount of work done, they can
range from 30 to 65 percent of operating losses.
    Controlling drag-out losses will substantially
reduce emissions into the workplace and, by using
the basic design parameters shown in construct-
ing a stripping bath, together with a lid, will reduce
further losses to the atmosphere.
    The further reduction of emissions and there-
fore user exposure  can be achieved by modified
formulations. As shown, these formulations differ

                                        MANUAL  ROLLER SHUTTER  LID

Figure 1.—Roller shutter for paint stripping bath.
                                                           RIM  VENTILATION
Figure 2.—Proportions of paint stripper bath.
substantially In their ability to self-skin and con-
tain the evaporation of the paint stripper.

Where emissions are controlled solely by space
ventilation  without  using canopies or other
methods, the following should be considered:

   • The air change rate should be 40 to 60
     percent per hour, and
   • The enclosure volume should be reduced
     as much as possible. This can be achieved
     by enclosing the process in a PVC-type of
     curtain in a dedicated room or separate

   The flow of air through the building should be
turbulent. The fans extracting polluted air should
be placed  opposite  vents  emitting fresh air.
Figure 3 diagrams bad, fair, and good air distribu-
tion with air fans.

                                                                    Reducing Risk In Paint Stripping
                 Bad                       Fair
Figure 3.—Good, fair, and bad distribution with wall fans.
The simple techniques outlined in this presenta-
tion show much can be done to reduce emissions
of methylene chloride and, hence, worker and user

Current Paint Stripping Practices
            Chair: Christine Whittaker
           Office of Risk Reduction Technology
             Health Standards Division
        U.S. Occupational Safety and Health Administration

Pollution Prevention Case Study:
Methylene Chloride  Substitution in  an
Automotive Plant
Jack Davis
William Reichert
Sanitation Truck & Bus Group
Flint Bus Assembly Plant
General Motors Corporation
Flint, Michigan
      The purpose of my presentation this after-
      noon Is to describe (1) the activities that
      Involved the use of methylene chloride
strippers at the Flint Truck Assembly Plant In the
early 1980s, and (2) the substitute products (and
operational changes) that we have Implemented
since then to replace methylene chloride. I will
explain not only the benefits of the switch from
methylene chloride, but also some of the com-
promises that we have had to make.
   Our plant Is part of the General Motors (GM)
Van Slyke Road Complex. The complex consists of
three separate plants: the Truck & Bus, Flint Metal
Fabrication Plant (which produces sheetmetal
stampings, frame parts, and.miscellaneous metal
components); the GM Power Train Division, Flint
V-8 Engine Plant (which assembles V-8 engines
and includes machining associated with this ac-
tivity); and finally, the  Truck & Bus Assembly
   At Truck & Bus we presently produce Blazer
and Suburban vehicles on two separate lines, and
Crew Cab vehicles. Since it opened in 1947. the
plant has operated two lines for most of its exist-
 Assembly Plant Operations

 The assembly plant operations consist of three
 distinct processes: welding, painting, and assemb-
   •  Welding consists largely of spot and mig
      welding of sheetmetal panels.
    Painting includes:

      • Washing the metal parts;

      • Treating the bare metal parts
       (phosphate and chromic rinses);

      • Applying a prime coat of paint (Elpo
       Dip Process); and

      • Applying topcoat paint to vehicle
       surfaces (base coat, clear coat).

    Assembly includes:

      • Installing the interior trim seats,
       electrical wiring,  and so forth, in the
       painted vehicle bodies;

      • Assembling the frame components,
       including the frame rails, springs,
       axles, transmission, engine, and so
       forth; and

      • "Putting It all together"—assembling
       the body to the completed chassis,
       then adding the remaining
Maintenance Operations

In addition to production, methylene chloride has
also been used In maintenance. The following
information is primarily from our response to a
1987 U.S. Environmental Protection Agency (EPA)
questionnaire created to gather information from
both industrial and commercial users of meth-
ylene chloride-based strippers.

    The advantages of using methylene chloride
were many and varied:

    • Low flammability, making It Ideal for use
      in highly hazardous locations such as the
      paint mix room and spray booths.

    • Fast "cold stripping," able to lift uncured
      paint almost Immediately and cured (oven
      baked) in a matter of minutes.

    • Excellent  stripping qualities—definitely
      the best cold stripper, it could be used on
      virtually any paint or surface, and required
      very minimal scraping.

    • Water  solubility, making it very easy to
      rinse off both the stripped material and the
      stripper itself.

    • Few skin or eye hazards when compared
      with caustic materials  such  as  sodium

    • Easy application—just lay it on and scape
      it up.

    • Relatively low odor and fumes, with less
      chance of asphyxiation compared  with
      other chlorinated strippers.
      These attributes made methylene chloride
      the  wonder  product  for paint  shop
      maintenance during the 1980s.

    This material was the primary cleaning/strip-
ping agent for three main areas at Flint Assembly:

    • Internal maintenance of the paint spray

    • Interior stripping of the paint supply lines
      located between the mix rooms  and the
      paint spray booths: and

    • Concrete floor stripping prior to
      Installation of protective coatings.

    Every day during during actual  production,
paint over-spray was stripped from the interior of
spray booths and equipment. In this operation the
stripper was applied to the walls, floors, and cell-
ings, allowed to set, and then rinsed off with water.
At this point, the paint is uncured and sticks to
virtually every surface it touches.
    During this period the plant was running two
shifts per day. leaving very little time for cleaning
up. Therefore, a product was needed that could be:

    • Easily applied (methylene chloride could
      be sprayed on the surfaces);

    • Relied upon to lift the paint quickly; and
    • Quickly rinsed off Into the booth water
     below (because it was mlscible in water,
     methylene chloride was Ideal for this).

    Dally cleanups were required when high-
solids enamel paints were substituted for lacquers
to meet air quality standards at Truck & Bus Flint.
Enamels, while better environmentally, left sur-
faces sticky. Methylene chloride was introduced at
the time (early 1980s) we switched to high-solids
enamels, and  presented a quick  and complete
solution to the new problems associated with this
Search for Alternatives

The EPA regulation controlling total toxic organlcs
(TTOs)—solvents—In the wastewater  stream
spurred us to replace methylene chloride. As part
of the pretreatment requirements for industrial
wastewater prior to its discharge into the City of
Flint's municipal wastewater treatment plant, a
very low total TTO limitation was placed on our
wastewater stream. One of the solvents on the TTO
list was methylene  chloride. We had to find a
substitute for methylene chloride that retained
many of its advantages.
    Fortunately, paint overspray In the booth is
uncured. making it easier to find a solution. Un-
fortunately, we still have not found a comparable
cold stripper for baked or cured paint.
    The TTO problems, combined with Impending
legislation on restricting methylene chloride use,
motivated chemical manufacturers to develop al-
ternatives. At Truck & Bus, we tried a number of
these substitutes, none of which worked as well as
methylene chloride in terms of stripping time. We
eventually settled on CLM 818. While CLM 818
does the Job, It does have a few drawbacks.

    • The material is slower than methylene
     chloride. Note that no mention of time is
     included in the ad.

    • This product must be washed off with
     water. The evaporation rate is slower, and
     in fact, the materials will leave gel
     residues if not rinsed off completely. The
     rinsing process affected our paint purge
     solvent collection systems, and forced us
     to install special drains In collection pans
     to allow cleaning during the third shift.
     Regular tie-in to the purge collection
     system is available during actual
     production during the first or second  shift.

                                                                      Reducing Risk In Paint Stripping
    • Both methylene chloride and the
     alternative product are not compatible
     with topcoat paints; however, the
     alternative cannot be used during actual
     production hours. Methylene chloride did
     not present as much of a problem because
     of its higher evaporation rate.

   Actually. CLM 818 was not the first product
we used, and is one of two we are presently using.
(An earlier version of CLM 818—called CLM 320—
required constant agitation to prevent settling in
its tote tank.) CLM 818 is presently used In the
Blazer-Suburban paint booths, while a Chemftl
product, PPG ChemifU  Polystrip #3450 (recently
replaced with #3480), Is used on the Crew-Cab
paint system booths. The difference between the
Chemfll and CLM 818 is that the Chemfil product
does not require the water rinse—the product itself
is used for rinsing, and any residues evaporate.
The disadvantage of this product was its odor.
Because of employee complaints, a new #3480 has
replaced #3450 (without the odor). If this product
is successful, we may test it on the Blazer-Subur-
ban system, eliminating contamination and water
rinsing required in our solvent collection systems.

Comparing the Alternatives

What is the principle behind these substitutes for
methylene chloride—what do they contain?  Al-
though supplier confidentiality  prevents  exact
descriptions, the primary ingredients for CLM are:

   •  Phenyl carbinol

   •  Aromatic hydrocarbon (naphtha)

   •  N-methyl pyrrolidone

   •  Trlmethylbenzene

   The  Chemfil product is primarily diacetone
   Most methylene chloride substitutes  contain
solvents such as  naphthas and alcohols. Also,
glycol ether was a major constituent of some of the
trial products. The products we presently use have
lower amounts, if any, of these constituents.
   The materials presently used also have other
severe restrictions  to formulation besides TTOs.
Cleaning materials containing products such as
toluene and  methyl ethyl ketone could con-
taminate the booth water, making it a F-code
hazardous waste under Resource Conservation
and Recovery Act (RCRA) guidelines. This could
make  all of the plant's Industrial wastewater an
F-code waste.
   With all of the chlorinated solvents eliminated
by TTO restrictions and most other good solvents
eliminated by RCRA, it really does require innova-
tion to come up with an effective stripper.
   In summary, for the first of our three prior uses
of methylene chloride, we have found substitute
products. We have sacrificed:

   • Speed—the  substitutes take longer  to
      perform the same operation;

   • Possible water contamination—some of
      the substitutes require greater rinsing;

   • Odor—resulting in  complaints  from
      employees; and

   • Stripping  ability—the substitutes cannot
      strip baked or cured paint.

   The second major stripping operation needing
a substitute for methylene chloride was the inte-
rior of the piping used to transfer topcoat paint
from the paint mix room to the spray booths. Paint
is stored in large  vats in a special explosion-proof
room; from there  it is transferred to spray booths.
With  10 to 20  miles of  piping, spraying ap-
proximately two to  four  gallons of paint per
minute, recirculation to the mix rooms is required
to prevent paint from settling out in the lines.
   To maintain the quality of the finished trucks,
a routine  procedure was developed to remove
paint, rust, and dirt from the interiors of the paint
recirculation system.  The same procedure was
used to  clean the system when removing an ob-
solete color.
   The standard procedure, developed over many
years, involved a nine-step cleaning process that
Included a methylene chloride stripping operation.
Other steps involved the use of various paint sol-
vents, as well as a caustic stripper, to ensure clean
lines. The cleaning materials were added to the
paint vat or tank, then circulated through  the
piping back to the tank, where contaminants were
collected. Filters, installed on both the supply and
return lines, ensure that these contaminants are
trapped and collected when returned to the tank.
Cleaning materials were collected and sent for
   Again, TTOs  in the wastewater precipitated a
change. Use of a caustic stripper following the
methylene chloride step caused a chloride residue
in the caustic solution. This chloride contamina-
tion In the waste stream presented a major treat-
ment problem when the caustic sodium hydroxide,
a water-based material, was sent to the waste-
water treatment plant for processing. To eliminate

the contamination, we added another step—an
alcohol rinse between the methylene chloride and
the caustic  steps. Alcohol was a non-TTO sub-
stance, so alcohol residues in the caustic stage did
not present a problem.
    While this helped, it really wasn't enough. The
whole operation became too cumbersome; residual
caustic  material  would be present in the next
solvent  rinse, which would contaminate the sol-
vent  to such  an  extent  that It  couldn't  be
reclaimed, resulting In a high disposal surcharge.
    After Investigating alternatives, we decided to
use a product from Gage Company: S-585 One-
Step Line Cleaner. This product:

    • Contains no methylene chloride or caustic

    • Requires fewer steps, saving time as well
      as cost;

    • Contains only solvents already used in
      topcoat paints (Xylene, etc.);
    • Allows use of either total recycling or the
      Chem-fuel alternative for disposal; and

    • Uses a grit or an abrasive substance to do
      the actual stripping, and a solvent to
      transport the abrasive material.

    The  abrasive stripper is currently used  for
paint line cleaning. The change was made last
year; so far the new method seems to be equal in
cleanliness to the nine-step process. However, we
continue to consider other alternatives. For  in-
stance,  we are preparing to evaluate the effective-
ness of a "pipeline pig" system that is used by other
GM facilities.
Stripping Floors

The final operation in which methylene chloride
was used would probably be considered a more
conventional use—stripping paint off  concrete
    Throughout our  plant, particularly In our
paint shops, we have concrete flooring coated with
urethane to ensure lasting wear. Keeping the paint
shop floors very clean helps promote good paint
quality, and is a major goal for the sanitation
department. Similar floor conditions are necessary
In other areas such as Audit, a highly visible final
inspection area.
    A regular routine was established for stripping
and reapplylng the urethane coating. A virtually
"new" floor was created each time, and the entire
process completed in a weekend.
    Methylene chloride-based products provided
the only quick and efficient method of removing a
urethane floor sealer from a large concrete floor
area. The material could be poured on and pushed
around with scrapers or squeegees. After setting.
the lifted urethane could be squeegeed  and
broomed to a central location to be shoveled up.
Only a minimum amount of scraping was neces-
sary—the removal process would take only a
couple of shifts on  Saturday, and the  new
urethane could be applied on Sunday. Without
methylene chloride, resurfacing an entire paint
shop floor with urethane in a weekend was impos-
    Employee  exposure was  a concern in  this
operation. Personnel performing these operations
were supplied with protective equipment, Includ-
ing respirators, gloves, aprons, boots, and hats. In
spite of this high level of protection, we decided to
find a substitute.
    We experimented with various products to find
something suitable. Two factors were involved:

    • The material being stripped was fully cured,
      and therefore the  stripping  requirements
      were more demanding than In our other two

    • This  was not a  regular  maintenance
      operation and we had more time for testing
      and evaluation—we Just put off stripping
      the floors.

    After many trials, we  never found a chemical
product to match the performance of methylene
chloride. The products tested either:

    • Didn't strip the floor material;

    • Stripped the floor materials to some
      extent but required lengthy periods of

    • Had handling problems, such as emitting
      terrible odors, were difficult to apply
      properly, required constant agitation,
      settled in the drums, were highly
      flammable—and still did only a borderline
      Job of stripping.

    What was our final answer for stripping floors?
We are using two distinct solutions today:

    • A switch In the product used to protect
      the floors from a urethane to a wax type of
      sealer; and

                                                                      Reducing Risk In Paint Stripping
    • A switch to mechanical floor stripping
     using scarifiers and application of a
     permanent epoxy coating.

    The wax type of sealer contains the following
Ingredients: water (80 percent), Dowlcll, leveling
agent, Carbitol, ethylene glycol, nonlonic surfac-
tant, polyethylene emulsion, and acrylic emulsion
    These materials have the  following ad-

    • Much easier than urethane to strip—we
     can use a wax remover containing such
     chemicals as: d-Limonene, light caustic
     acid, phosphates, or substitutes described
     for the first operation—glycol ethers,
     alcohols, naphthas, or a combination

    • Quick and easy to apply.

    • Dry very quickly compared with urethane,
     allowing the floor surface to be back in
     service much faster.

    • Lower odor levels and less flammable
     compared with  the high solvent that
     contains urethane. This results in greater
     safety, fewer employee complaints, and
     less protective equipment required.

    However, the material does have some disad-

    • It Is not as durable and has to be replaced
     more often. Ease of removal makes it
     easier to wear off or be stripped off by
     regular use. Therefore, it has to be
     reapplied considerably more often.

    • More product is needed to obtain
     adequate protection, resulting In higher
     purchase and labor costs.
    • It does not provide the new look that the
     urethane provided. The surface does not
     have a high gloss.

   Although more expensive, the epoxy coating
provides a "permanent" surface. It consists of the
following steps:

   •  Mechanically removing the  floor coating
      using a powerful  tennant scarifier, which
      also roughs up the concrete to allow super

   •  Applying 1 /4" to 3/8"-thick coating of super
      epoxy, leaving a surface which is virtually
      impenetrable,  super smooth,  and super
      glossy; one that can be maintained with

   Epoxy offers a more permanent  solution—the
resulting surface is extremely durable, has a very
glossy, clear appearance, and is very smooth and
easy to clean. Epoxy, however, has several disad-

    • Requires much more preparation and

    • A heavy duty scarifier must be used;

    • Creates a considerable amount of dust;
     and, most importantly.

    • Is very, very expensive, normally running
     from $5 to $10 per square foot, depending
     on the product.

   We are currently using both of those methods
in our plant. The  Line #2 Paint Shop Floor Area
has been largely resurfaced with the epoxy
   This is our story. We  hope it helps you under-
stand assembly plant requirements  for methylene
chloride in stripping operations. We have spent
much time searching for and testing  potential
substitutes, and continue to search for more effec-
tive, less expensive solutions.

An  Overview  of Paint  Stripping  Practices
in the  Metalforming  Industries
John F. Grainger
Turco Products, Inc.
A Division ofAtochem North America
Westminster, California
        Virtually  any industry that fabricates
        metal parts will have recurring need to
        salvage  or  rework  rejected parts.  Al-
 though most  Industries have embarked  on
 programs to enhance quality and minimize bad
 production, rejects still occur. Since many if  not
 most metal parts are coated with some type of
 organic coating, either functional or decorative,
 this reworking often involves removal, or stripping,
 of that coating. The  decision to rework or scrap
 depends on the value added to the part In prior
 manufacturing steps plus the cost of reworking as
 opposed to the cost of disposal. Usually these
 economic considerations favor reworking.
    Industrial paint stripper users span the gamut
 of manufacturers, from the automotive to  the
 electronics Industry. Included  are such diverse
 products as typewriters, computers, oil rig equip-
 ment, earth  moving equipment, aircraft ground
 equipment, military ordnance (Including ammuni-
 tion and bombs), large and small household  ap-
 pliances, office furniture, highway signs and
 signals, and even caskets.
    Although each of these industries needs to
 strip rejected or reworked parts, they differ widely
 in the methods chosen to accomplish this. Several
 factors are used to evaluate and select  these
 methods. First and foremost, of course. Is cost. The
 added cost of stripping and refinishing rejects
 must be recoverable  or at least be less than  the
cost of scrapping the part. Beyond that, the strip-
per must be safe  on the substrate and for using
and operating personnel, and it must be relatively
economical to dispose of at the end of its useful
   When such a product is identified, an In-house
specification Is often  written based on  that
product. This tends to lock in place the product
and the procedure. The overall effect of this Is to
delay if not discourage Introduction of new and
especially innovative products. Few department
heads or supervisors seek out the dubious honor
of being the first to prove that a new process will
work. Unless the operation is disrupted or outside
pressure, such as a new regulation, is brought to
bear, most seem content to let well enough alone.
   The basic technology of paint stripping Is
based almost entirely on empirical observation.
The actual mechanisms of stripping are not well
understood or firmly grounded in theory. Predic-
tion is erratic at best, and most often, when a new
part or paint Is to be stripped, the most practical
approach is to  select a few strippers that  have
worked on similar parts or paint schedules in the
past  and evaluate their performance on the new
part or  new paint to be stripped.
   In discussions of paint strippers or paint strip-
per technology. It is useful to categorize the many
available strippers into  groups and discuss each
group as a whole. Strippers may be characterized
by the type of paint they are meant to strip—epoxy
strippers, lacquer strippers, etcetera—or by the
method of application—thickened, spray-on strip-
pers, hot tank immersion strippers, and so forth—
or by their principal components. The last category
is probably the most informative and  will be the
method of classification here. Generally, distinc-
tions are clear cut, but occasionally an ambiguous
case  arises and classification Is  then based on
secondary characteristics.

                                                                      Reducing Risk in Paint Stripping
   For this discussion, paint strippers will be
divided into three broad categories:

   • Aqueous (water-based) strippers. Water is
      the major liquid solvent present, although
      organic solvents may institute up to about
      20 percent of the composition.

   • Solvent-based strippers. Organic solvents
      are the major liquid components, although
      water may be up to about 35 percent of the

   • Mixed  or  semi-aqueous  strippers.
      Appreciable amounts of both water and at
      least one liquid organic solvent are both
      present in amounts ranging from 4O  to 6O
Aqueous Strippers
Water-based or aqueous strippers Include both
caustic and acid products. The caustic strippers
are the most widely used in this category.
   Caustic strippers generally contain from 10 to
20 percent sodium hydroxide (or less frequently.
potassium hydroxide). These are among the very
oldest Industrial paint strippers for metal parts.
They generally include  substantial amounts of
caustic stable surface active agents (or surfactant).
chelating agents, and up to 20 percent organic
solvents. These additives are necessary to strip
some of the more resistant paints. Caustic strip-
pers In general are almost  always used in an
immersion  process In which Individual parts or
baskets of parts are Immersed In the solution until
stripping is completed.  These  products  are
operated hot. at temperatures ranging from 180*F
to 240*P. The aqueous products usually work by
a chemical attack on the paint film, degrading it to
a sludge-like consistency that is  then rinsed from
the parts.
   The principal advantages of this class of strip-
per are the relatively low chemical and disposal
costs. Disadvantages are that they are effective on
a limited number of coatings, are safe only on
magnesium and ferrous metal parts, incur high
energy costs in operation, and are hazardous to
the operator.
   These products were formerly a mainstay in
the automotive and heavy equipment industries,
but that use has declined as more  resistant coat-
ings have been introduced. Current users include
manufacturers of such  home appliances as  hot
water heaters, gas heaters, and air conditioning
units. Paint hook stripping is also a popular use
for these products.
    Other aqueous strippers Include hot solutions
of sulfurlc or chromic acid, but their use Is general-
ly restricted to coatings impossible to remove by
other means within time constraints.
Solvent Paint Strippers

Currently the most important paint stripping for-
mulations have a solvent base. These strippers are
the most widely used in the Industry. This would
include both products thickened for spray applica-
tion and those thinned for  immersion, hi  both
sub-types may be found acid or alkaline materials.
chlorinated and nonchlorinated products. For this
discussion, solvent paint strippers will be divided
into chlorinated and nonchlorinated products.
    Among chlorinated solvent-based paint strip-
pers, the premier  solvent Is usually methylene
chloride, although In a few immersion-type
products, orthodichlorobenzene, trlchloroethane.
and perchloroethylene also are used. Use of these
other chlorinated solvents may allow the stripper
to be used hot. at temperatures as high as  140* to
160*F. Methylene  chloride-based products, be-
cause of their 104*F boiling point, cannot be used
above about 90*F without incurring substantial
evaporation losses. Together with the chlorinated
solvent base, these products generally contain 10
to 30 percent co-solvents, usually alcohols.
ketones. esters, and/or aromatic solvents such as
toluene; 5 to  15 percent water plus so-called ac-
tivators such as ammonia, various amines, formic
acid, phenol, cresol. etcetera.  Finally, they may
contain minor amounts of surfactant, thickeners.
corrosion inhibitors, and  evaporation retardants.
If the product is used in an Immersion process, it
may have 10  to 15 percent water or oil to form a
floating layer as a seal to retard evaporation. These
products—generally  potent mixtures—are suc-
cessful on the more difficult stripping jobs.
    The viscous, spray-on products are used for
large parts  or assemblies  that cannot  be Im-
mersed,  for detail stripping where only  certain
areas need to be stripped, and for stripping small
quantities of parts whose numbers do not justify
the Installation expense of an Immersion stripping
    These strippers, whether thick or thin, are
versatile, effective, and  reasonably  economical.
They are so popular that they might be found  in
any industrial setting. They would certainly be the
product of choice for most applications  If there

were not so many health and environmental con-
cerns about their use.
    These concerns  currently center around
methylene chloride Itself. Methylene chloride has
been among the most widely studied of the com-
mercial  organic solvents. There Is a broad
database covering the health effects on humans
exposed  to various levels for extended periods of
time,  up to an entire working lifetime. The sig-
nificance of  this data, combined  with  animal
studies of various species exposed In various ways,
Is the subject of some debate. Wherever the truth
lies, however, the problems associated with its use
are well  known and technologies exist to control
these problems.
    Naturally there Is a considerable impetus to
avoid these problems  altogether by using a strip-
per based on solvents  other  than  methylene
chloride  or other halogenated  hydrocarbons.  It
should always be kept In mind, however, that
alternate solvents or technologies may appear to
be  advantageous by comparison  only because
much less is known about the alternative ap-
proach. The old adage still applies that "absence
of evidence Is not evidence of absence."
    The  other broad  category  of solvent-based
products is  nonchlorlnated solvents. These In-
clude such diverse materials as N-methyl pyrrol-
lldone, various glycols or glycol ethers, dimethyl
sulfoxide. and others. These solvents are difficult
to classify Into a coherent group, but they usually
seem to be fairly polar, water soluble, and capable
of entering into hydrogen bonding. These products
generally Include a high concentration (30 to 40
percent)  of an alkyl or alkanolamine and an oily
layer  as  a seal to retard evaporation. They are,
almost without exception. Immersion products.
    Because  they tend to be much slower acting
than  methylene chloride-based products, these
strippers are  operated hot, from 140° to 250°F. At
these elevated temperatures, they are quite effec-
tive and approach or even  surpass the perfor-
mance of methylene chloride-based strippers.
They seem to more selective  In their action, how-
ever, and do not usually strip as broad a spectrum
of paints as a methylene chloride-based product
    Products  of this type are currently used to
strip rejected parts in a host of industries includ-
ing office equipment and furniture, aircraft and
automotive wheels, turbine engine manufacture or
remanufacture, casket manufacturing, oil drilling
rig equipment, wellhead equipment, and air con-
ditioner and air compressor  manufacturing. This
list would be as varied as  that for chlorinated
    These products suffer  from several  disad-
vantages. First, the initial cost is usually substan-
tially higher—sometimes three times as high as an
effective methylene chloride product. This initial
high cost, however, is usually balanced somewhat
by longer tank life and lower disposal costs. High
operating temperatures cause high operating
costs because of high energy costs. Stripping may
be somewhat slow and selective.
    The chief advantage of these products Is the
absence of chlorinated solvents. Generally these
products are formulated to also eliminate other
Ingredients that cause disposal problems, such as
chrome and phenols or cresols.
Mixed or Semi-aqueous

This last category Is the newest of the three clas-
sifications. There are  not  many representative
products in this group, but they are attracting
considerable Interest. Mixed or semi-aqueous
strippers  contain nonchlorinated solvents and
water in roughly equal portions. Based on current
information, they seem to be relatively innocuous
to both the user and the environment. They strip
even the most  resistant  aircraft and aerospace
paints and are available for both Immersion and
spray-on applications. Since these are relatively
new products, they are not In wide use.
    Products In this category are currently used to
strip rejected parts for manufacturers of heavy
equipment, oil rig drilling equipment, aircraft and
aerospace equipment, computers, railroad rolling
stock equipment, and many other types.
    Mixed products offer several significant  ad-
vantages. First,  this category Includes the only
nonchlorlnated thickened strippers that are effec-
tive on the most resistant paints, such as epoxy
primers. Thickening allows use on large parts or
assemblies that cannot be immersed in a strip
tank. Second, mixed products are relatively easy
to dispose of since they generally are free of the
chrome, phenol, and other components that create
disposal problems.  Any waste  rinsewater
generated during their use is also relatively easy
to handle.
    Disadvantages  of mixed or semi-aqueous
strippers include their relatively high cost com-
pared  to chlorinated strippers. This high Initial
cost may be completely or partially  balanced by
lower overall operating costs, however. A second
disadvantage is  longer stripping time,  although
this may be a more apparent than real drawback,
as usually only  15  to 45 minutes more time is

                                                                       Reducing Risk In Paint Stripping
required, which is often insignificant In the entire     tinue to be  the most widely used type of paint
strip and repaint schedule.                         stripper, in spite of the increasing problems as-
                                                 sociated with their use. Gradually, as regulations
                                                 become more and more restrictive, more and more
                                                 companies are changing to the nonchlorinated
                                                 solvent-based or semi-aqueous variety of stripper.
Summing all of this up. it would appear  that     u is expected that this change will continue at a
chlorinated solvent paint strippers and. In  par-     gradual pace unless new regulations or restric-
ticular. those based on methylene chloride,  con-     tions accelerate this process.

  Substitute Solvent
 Non-solvent Alternatives
        Chair: Christine Whittaker
       Office of Risk Reduction Technology
         Health Standards Division
    U.S. Occupational Safety and Health Administration

NMP Formulations for Stripping  in the
OEM  Market Sector
Carl J. Sullivan
ARCO Chemical Company
Newtown Square, Pennsylvania

AT-methyl pyrrolidone (NMP) is a recognized alter-
native to methylene chloride-based solvent sys-
tems as well  as  other organic-based solvent
systems because of Its known effectiveness (Pal-
mer, 1978; Nelson, 1988; Hearst, 1987; Francisco,
1988; Werschulz, 1986) and very low volatility. The
low volatility drastically reduces the flammability
hazard (NMP's flash  point is  199°F). The low
volatility also reduces evaporative losses that con-
tribute to worker exposure and environmental pol-
lution. A major drawback  to NMP usage in this
industry is Its high cost. Although very effective on
most paints, the cost of NMP makes it prohibitive
to use as the sole solvent In a stripper formulation.
    The purpose of our recent research program
on paint stripping compositions has been to ex-
amine NMP solvent blends and attempt to define
synerglstic combinations that will have several key
characteristics: effectiveness, low cost, low
toxicity, low volatility, high flash point, environ-
mental acceptance, and potential recyclability. No
one blend is expected to fulfill all requirements,
but synerglstic solvent combinations would be
applicable by simple adjustments to very specific
market niches.
Experimental Procedures

Solutions were spot tested on the paint panels for
stripping effectiveness. For cured alkyd and epoxy
coatings (see Appendix A for formulations), only
film lifting from the substrate was considered ef-
fective removal. The time between application of
the solvent blend to the panel and the time neces-
sary for complete lifting of the film was defined as
the "lift-time." The average  of three spots was
reported. All experiments  were done  at room
   Solvent blends were also tested on uncured
automotive paints: a black enamel, white enamel,
and a solvent-borne clear coat over a waterborne
base coat. Effectiveness of the solvent blend was
measured by applying several drops to the air-
dried paint (for 2 days), covering the spot, and,
after 10 minutes, gently wiping the film surface. A
relative performance scale of 0 to 5 was used with
0 = no effect; 1 = 0 to 30 percent paint removal; 2
= 30 to 50 percent paint removal;  3 = 50 to  70
percent removal; 4 = 70 to 90 percent removal, and
5 = >90 percent removal.
   All solvents were obtained from Aldrlch Chemi-
cal Company or Fisher Scientific with the excep-
tion of the following Items: N-methyl pyrrolidone,
Gamma-butyrolactone, ARCOSOLV*PM Acetate
propylene glycol monomethyl ether acetate, and
ARCOSOIA^DPM Acetate  dipropylene glycol
monomethyl ether acetate, which are products of
ARCO Chemical Company. Aromatic 150 and
Isopar*M are products of Exxon Chemical Com-
pany. XTOL*P tall oil fatty acid is a product of
Georgia Pacific Corporation.

 ARCO has focused Its attention on NMP because
 of general Industry knowledge that NMP works
 very well by Itself. In addition, NMP-aromatic sol-
 vent blends demonstrate stripping effectiveness
 roughly equivalent to NMP alone (Palmer, 1978).
 However, before screening numerous solvent
 blends, we compared NMP to several other sol-
 vents and a methylene chloride-based blend. The
 results are listed in Table 1.
    This test was performed in part to assess the
 efficacy of this experimental technique for screen-
 Ing relative performance of solvent-based strippers
 as well as making comparisons of NMP to other
 solvents. The test was simple, fast, and considered

Table 1.—Performance of paint stripping solvents.
Methylene chloride + toluene
+ methanol (85/10/5)
A/-methyl pyrrolidone
Furfuryl alcohol
DBE (dibasic esters)1
Propylene carbonate

No Lift
No Lift
No Lift
No Lift
No Lift
No Lin
No Lift
No Lift

'Product of DuPont Corporation

to be very reliable for making simple comparisons
of one solvent system to another.
    As indicated In  Table  1, the  methylene
chloride-containing solvent blend stripped the
alkyd  coating the  fastest; however, after  60
minutes, the lifted film dried out and re-adhered
to the aluminum substrate. Clearly, speed is an
advantage but the evaporation rate can be a prob-
lem because  of readhesion. NMP is  the second
fastest at lifting the film and no readhesion occurs
because of the slow evaporating characteristic of
NMP. Acetophenone is somewhat slower but still
effective at lifting the film. The remaining solvents,
some  of which are claimed to be effective paint
strippers In combination with  other  active sol-
vents, fail to cause lifting. Although some of these
solvents soften the film and enable removal with
scraping, mechanical work Is necessary to get the
film off the surface.
    While pure NMP is a very effective solvent for
stripping, it is not an economically favorable op-
tion. Blending NMP with other organic solvents
can lower cost but, typically, performance is lost
(as  indicated in Table 2). Propylene  glycol
monomethyl ether acetate-NMP blends are not as
effective as NMP. and performance decreases when
glycol  ether acetate content Is increased.

Table 2.—Effect of diluent on stripping performance
of NMP-based solvent systems.
No Lift
No Lift
 'ARCOSOLV PMAcetate (propytene gyteol monomethyl ether acetate)

    Stripping effectiveness of an NMP  solvent
blend is expected to be dependent upon the type
of cosolvent. A broad series of cosolvents have been
screened to determine relative effectiveness of dif-
ferent cosolvent classes as diluents for NMP-based
stripper compositions. The results, which have
been discussed elsewhere (Sullivan, unpubl.), in-
dicate  two general controlling trends, as  sum-
marized in Figure 1.  First, NMP performance is
inhibited by polar solvents, whereas nonpolar sol-
vents provide synerglstic benefits. Secondly, for a
group  of diluents with  approximately the  same
polarity, the performance increases with Increas-
ing volatility.  However,  the  implication of this
second trend is that flammablllty concerns conflict
with performance.
                                Cosolvent polarity

                                   • Performance Increases as cosolvent
                                     polarity decreases.
                                   • Glycol ethers and glycol ether
                                     acetates show good performance in
                                     combination with NMP.
                                   • Aromatic solvents show synergy.

                                Cosolvent volatility

                                   • Performance increases as cosolvent
                                     volatility increases.
                            Figure 1.—General trends on diluent effects of NMP
                            eolvent blende.
                             Ternary Blends
                             Perhaps the most Interesting aspect of this screen-
                             ing study is the crude relationship between cosol-
                             vent  polarity and effectiveness.  Very nonpolar,
                             low-cost solvents such as mineral spirits are not
                             miscible with NMP. but the trend suggests that
                             NMP blends with mineral spirits might perform
                             very well. To test this hypothesis, two different
                             ternary solvent blends were formulated and com-
                             pared to binary blends. The results are provided
                             In Table 3.
                                The ternary blends of Table 4 show increased
                             performance relative  to the binary blends. How-
                             ever, the NMP content is significantly lower in both
                             of the ternary solvent blends; therefore, the cost of
                             the formulated products will be lower.
                                A possible explanation for this unusual be-
                             havior may be the subtle differences  in surface
                             wetting and phase partitioning at the coating-sol-
                             vent blend interface. NMP is not miscible with
                             mineral spirits; therefore, NMP may have a strong
                             thermodynamic driving  force to  phase separate
                             from the mineral spirits blend and diffuse Into the
                             moderately polar paint film (Fig.  2). Surface wet-

                                                                         Reducing Risk In Paint Stripping
Table 3.—Relative performance of ternary NMP blends.
                           _ LIFT TIME (MINUTES)
A. 40% NMP
   60% ARCOSOLV PMAcetate
B. 33% NMP
   33% Mineral spirits
   33% ARCOSOLV PMAcetate
C. 40% NMP
   60% Aromatic 150'
D. 31% NMP
   47% Mineral spirits
   22% Aromatic 1 SO1

'Aromatic 150 is a product of Exxon Chemical Company
Table 4.— Non-methylene chloride strippers.
Mineral spirits
Isopar M
Aromatic 150
Flash Point (°F)
Relative Performance2
Black enamel
White enamel

B C D'




'U.S. patent 4,120,810
'Covered spot (10-minute soak), 0-5 relative scale, see text

ting  will clearly play a  significant role in  such
phase partitioning, and surfactants can obviously
influence this partitioning.
   Because NMP is immiscible  with aliphatic
hydrocarbons, a third solvent is necessary to get
both the synerglstlc and  cost-reducing benefits of
the aliphatic hydrocarbon. Interestingly, the pos-
sible range of such combinations  is limitless be-
cause of the large variety of solvents that can be
chosen as the  mlsclbilizlng agent. Also, a large
variety of low-cost aliphatic solvents are available
to the formulator.
               Examples of other formulation options  are
           listed in Tables 4 and 5. The relative performance
           data  for these blends  on the  three air-dried
           automotive paints are provided.

            Table 5.—Non-methylene chloride stippers—no
            aromatic content.
Mineral spirits
Isopar M
Rash Point (°F, SETA)
Relative Performance*
Black enamel
White enamel






                         'Covered spot (10-minute soak), 0-5 relative scale, see text

                           The examples of Table 4 depict NMP-aliphatic-
                        aromatlc blends with  varying composition and
                        flash points. Versatility is a key advantage of these
                        ternary blends. Not only are the blends cost effec-
                        tive, but the flash point is  readily adjusted by the
                        appropriate choice of cosolvents.  Higher flash
                        cosolvents, such as isopar M and aromatic 150,
                        yield higher flash blends.
                           In Table 5, a range of solvent blends is provided
                        that do  not contain  aromatic solvents for those
                        markets where the user prefers to avoid aromatic
                        solvents. The blends lift the paint films effectively
                        and, as in Table 4, the flash points vary depending
                        upon the flash points  of the cosolvents that are
                        chosen. Versatility is again  a clear advantage of
                        these  ternary blend systems. The glycol ether
                        acetates make good  compatibillzers as does the
                        XTOL*P—a product derived  from tall oil fatty
                           For all of the blends of Tables 4 and 5, relative
                        performance has been based upon the ability to
                                                                            Solvent  Blend
                                                            Paint  Film
Rgure 2.—Sch«matlc of solvent blend, paint film, substrate Interface.

easily wipe the air-dried film from an aluminum
substrate after only 10 minutes soak time. For
more difficult films and thicker layers of films,
such as the solvent-borne clear coat over the
waterborne base coat, longer contact times will
ensure  complete removal  of the partially dried
    Clearly, the blends described here should pro-
vide a great deal of versatility to the formulator in
the industry. Thickeners are often required, and
ethyl hydroxyethyl cellulose (available  from
Aqualon*) is very effective for some of the ternary
blends.  Activators, such as  formic acid, are
claimed to  add  stripping power to methylene
chloride-based formulations. However, such ac-
tivators should be examined for utility in these
novel blends.

NMP is a  proven performer for paint stripping
applications. The work reported here summarizes
new concepts in blending NMP with other organic
solvents to provide effectiveness and  economic
viability. The NMP ternary solvent blends have
unique attributes, primarily because of the broad
formulation options available to the end user. Low
volatility, cost-effective formulations that yield
high flash-point products are obtainable.

Francisco, R.L.  1988.  Paint Stripping Composition
    Having Reduced Toxlcity. U.S. Patent #4,732.695.
Hearst, P.J. 1987. Stripping Agent for Chemically Resis-
    tant Coatings. Statutory Invention Reg. H300.
Nelson, H.J.  1988.  Paint Stripping Composition and
    Method of Making and Using the Same. U.S. Patent
Palmer. D.A. 1978. Paint Remover with Improved Safety
    Characteristics. U.S. Patent #4,120.810.
Sullivan, C.J. Solvent Based Paint Strippers: Alterna-
    tives to Methylene Chloride. 1990 Annu. Meet. Fed.
    Soc. Coatings Technol. (Copies available from ARCO
    Chemical Co. upon request).
Werschulz, P. 1986. Reduction of total  toxic organlcs in
    metal finishing wastewater, alternative paint strip-
    pers. Pages 328-56 In Toxic Hazard. Wastes, Proc.
    Mld-Atl. Ind. Waste Conf.

                                                            Reducing Risk In Paint SMppIng
                              APPENDIX A

           Formulations for Cured Alkyd and Epoxy Coatings
White Alkyd Air Drying Enamel
                   White Epoxy Polyamlde Enamel
Mineral Spirits
Thlxatrol GST
TIPure R-900
Part A

Araldlte 471-X-75
SR-82 Slllcone Resin
TIPure R960
Mineral Spirits
6% Cobalt Drier
6% Zlro Catalyst
5% Calcium Drier
Antl-Sklnnlng Agent

Araldlte 471-X-75
Arcosolv PM

                                              900 Lbs
                                            84.89 Gal

                                             Hardener HY-815


                                              100 Lbs
                                             12.35 Gal
931.0 Lbs
100.0 Gal
1000 Lbs
 973 Gal

 Aromatic Solvent Strippers  for
 Automotive  Paint Booth  Maintenance
 Harry Seifert
 Haas Corporation
 Philadelphia, Pennsylvania

 Several automotive assembly plants are now using
 paint strippers based on aromatic solvents for
 paint booth cleaning. These products offer a cost-
 effective replacement for methylene chloride paint
 strippers, while maintaining an acceptable level of
 performance. The use of these products does not
 require  the extensive equipment or  procedural
 changes necessary for other  methylene chloride
 Alternative  Paint Strippers

 The aromatic solvent strippers described here are
 used exclusively on uncured paint and are most
 frequently used to clean oversprayed paint from
 paint booth walls, windows, and equipment. These
 thlxotroplc materials are applied by low-pressure
 spray or flow onto the coated surfaces and allowed
 to contact the surface for 5 to 10 minutes. After
 sufficient time has passed, the surface Is rinsed
 with high-pressure water to remove  the stripper
 and paint residue.
   A typical formulation of an aromatic solvent-
 based stripper contains 50 to 80 percent aromatic
 solvent, 5 to 30 percent of a cosolvent, and varying
 amounts of emulslfler, thickener, and odor mask.
 If desired. The aromatic solvent used as a base Is
 a petroleum naphtha with a flash point between
 105 to 155°F. These solvents are somewhat active
 alone, but performance is greatly enhanced by the
 use an active cosolvent. The choice and amount of
 cosolvent have  the most pronounced effect on
   Applicable solvents Include N-methyl pyrroll-
done, furfuryl alcohol, the whole range of glycol
ethers, and esters. In many cases It Is helpful to
utilize a combination of solvents to widen the
application range of the stripper.
   The use of emulslfler In these formulations Is
intended to Improve rinsing with water. Anionlc
surfactants are generally preferred, as they are
less likely to Interfere with paint detacklflcatlon or
cause problems with existing waste  treatment
processes.  However, small amounts of nonlonic
surfactants are also used to reduce streaking of
the surfaces after rinsing.
   The use of a thickener is most Important with
materials used on paint booth walls. The proper
viscosity and flow characteristics are  critical In
minimizing the amount of stripper necessary to
clean a given area. The material must be easily
pumpable, yet cling to vertical  surfaces long
enough for the stripper to be effective. If the proper
viscosity Is not achieved, multiple  applications
may be required, increasing volatile organic emis-
sions and costs. A variety of thickeners can be
used. Including cellulosics in systems with high
cosolvent content.
   The primary hazards associated with these
strippers are due to the flash point and the poten-
tial exposure to solvent vapors. Since  these sol-
vents can  contain varying amounts of xylene,
toluene, ethyl benzene,  and  naphthalene, ex-
posure to vapors should be minimized with protec-
tive breathing  devices. While these  materials
continue to contain hazardous Ingredients, they
do offer a significant advantage over methylene

In almost all cases, methylene chloride strippers
remove paint more quickly than these products in
laboratory tests, but the difference in performance
is insignificant considering plant practices. Since

                                                                       Reducing Risk In Paint Stripping
it requires a substantial amount of time to coat a
paint booth, strippers generally remain In contact
with the painted areas for at least 5 minutes. This
allows for the use of a somewhat slower stripper
than methylene chloride.  (See Figures 1. 2 and 3
for a comparison of time  required to remove dif-
ferent types of paints.)
              20 r
      Me Cl    Formula A  Formula B   Aromatic

Figure 1.—High-solids enamel.
20 r
      Me Cl    Formula A   Formula B

Figure 2.—Polyurethane clear coat.
    The effectiveness of aromatic solvent strippers
on typical automotive finishes depends largely on
                   Me Cl    Formula A  Formula B   Aromatic

              Figure 3.—Two-part clear coat

              the type and content of the cosolvent. High-solids
              enamels can be effectively removed with materials
              containing relatively low (10 percent) concentra-
              tions of cosolvent, while polyurethane clear coats
              require a significantly higher concentration  (25
              percent) of cosolvent. The new two-part clear coats
              are especially difficult to remove and may require
              multiple applications or the  use of even  higher
              cosolvent concentrations. (See Table 1 for  typical

              Table 1.—Typical formulations.

Aromatic solvent
Waste  Management

In a typical assembly plant operation, both strip-
per and paint residue are washed Into the detack-
ification system. When properly managed, this
additional wastewater, paint, and stripper should
not cause any problems with the normal function-
Ing of the system.
    Since the majority of the stripper  is volatile,
paint is the most significant component entering
the treatment system. In plants where an aqueous
detacklfication system is not In use,  the wash-

water from stripping can be collected and treated
separately  with  acid/polymer or alum/polymer
combinations  to remove emulsified solvent and
paint solids.

The material cost of aromatic solvent strippers is
generally 10 to 50 percent higher than  their
methylene chloride counterparts on a pound-for-
pound basis. However,  training of maintenance
crews  In the proper application of thin stripper
films and the formulation of products to provide
good clinging properties can minimize the use of
these products. In many cases, the overall cost of
stripping is comparable  to using methylene
chloride. One  of the major advantages to this
system as opposed to  other alternatives  is
simplicity. These materials are used In very much
the same manner as the previously used strippers
and require very little investment In equipment.
space, and manpower.
   Other  practices and products are constantly
being developed to decrease the amount of stripper
used to reduce costs, volatile organlcs, and worker
exposure.  One of these practices is the use of a
water soluble coating that is applied to the booth
after cleaning. This coating makes the paint easier
to remove, allowing for less frequent stripping.
Continued work In this direction should eventually
lead  to strippers that do not use hazardous  or
volatile solvents to clean paint booths.

Alternative  Methods for  Uncured  Paint
Removal  In  Automotive  Manufacturing
R. Jeff Meade
Frank C. Burinsky
Nalco Chemical Company
Napervllle, Illinois

Historically, methylene chloride served as the
primary chemical agent for paint spray booth
cleaning in automotive assembly plants.
Methylene chloride was the active ingredient in
thickened solvent paint-stripper formulations that
were applied to  oversprayed paint deposits  on
spray booth surfaces at the end of the production
shift. After allowing adequate time for reaction,
softened paint deposits and paint stripper were
washed with water into the spray booth water
   Methylene chloride exhibited a number of uni-
que qualities that made it especially useful  for
paint spray booth cleaning. These were (1) a high
degree of efficacy in softening and/or dissolving
paint deposits, including cured paints; (2) safety
with regard to fire risk, due to methylene chloride's
high flash point; and (3) low contribution to volatile
organic compound (VOC) emissions, as a result of
methylene  chloride's classification as  non-
photochemically reactive.
   Unfortunately, methylene chloride also pos-
sessed a number of less desirable characteristics
that eventually resulted in its virtual elimination
from use in automotive  assembly spray booth
cleaning. These Include (1) suspected deleterious
health effects for chronically exposed workers; (2)
classification as a priority pollutant with regard to
wastewater discharge requirements for total toxic
organics (TTO) under the Clean Water Act; and (3)
operational drawbacks caused by its  rapid
evaporation rate and its tendency to leave  In-
soluble pigment film on spray booth surfaces fol-
lowing water rinsing.
   By the mid-1980s, automotive manufacturers
had largely replaced methylene chloride-based
products with alternative solvent blends, primarily
over concern for the health of chronically exposed
   Concurrently, a major  change in paint for-
mulation technology aided  automotive manufac-
turers in shifting from methylene  chloride to
alternative, nonhalogenated solvents. Low-solids
lacquer paints were largely replaced by high-solids
enamels and base-coat/clear-coat technology to
meet more stringent volatile organic compound
emission standards. Methylene chloride had been
particularly useful to the booth cleaning operation
because of its unique ability to remove air-cured
lacquer paint.  While higher-solids paints pose
their own cleaning challenges, they require heat to
cure. A variety of nonhalogenated solvents were
soon Identified that exhibited varying degrees of
effectiveness in dissolving the uncured deposits of
paint using the new paint technologies.

Replacement Formulations for
Methylene  Chloride

Numerous formulations have been developed for
nonhalogenated  solvent-based paint strippers.
Typically, these consist of a hydrocarbon solvent
and a more polar cosolvent. Thickening agents,
surfactants, and other additives are often Incor-
porated into the formulas.
    hi general, alternative solvent formulations
compare to methylene chloride as follows:

    • Stripping activity: New formulations
      provide comparable effectiveness. Losses in

      time were compensated by changes in work
      schedules and methods.

    • Fire safety: A number of nonhalogenated
      solvents with high flash points (greater than
      100°F or 140°F) have been employed. While
      fire  risk versus methylene chloride is
      somewhat greater, the routine high safety
      standards of the spray booth have
      minimized this drawback.

    • Volatile organic compound  emissions:
      Unlike  methylene chloride formulations,
      essentially all of the solvent portion of the
      new formulations contributes to VOC

    • Health effects: While chronic exposure to
      any  organic  solvent  is  considered
      potentially harmful,  the replacement of
      methylene chloride is  generally believed to
      be a positive step.

    • Total  toxic organics contribution:
      Replacement of  methylene chloride
      generally Improved  plants'  ability to meet
      waste water discharge requirements.

    • Application considerations: Replacement
      formulations generally  contain  slower-
      evaporating solvents. However, Insoluble
      pigment film remaining after water rinsing
      continues to be a problem.

    While the conversion from methylene chloride
to other technologies for booth cleaning has been
largely completed In the automotive assembly In-
dustry, a number of concerns remain. The advent
of the Clean Air Act amendments makes the reduc-
tion of volatile organic compound emissions from
the booth cleaning operations an Increasingly im-
portant issue. Balancing  the reduction of VOC
emissions within the constraints of cost perfor-
mance goals, limited time schedules, and respect
for worker safety will be the challenge of the 1990s.
    In developing a booth maintenance program to
reduce VOC emissions, a number of different op-
tions were investigated. A major constraint was
that the program had to provide comparable per-
formance in the same time frame  as  existing
    New paint stripping tests were developed to
quantify  paint stripper usage. These tests were
then conducted on different degrees of paint over-
spray to  generate conditions that would better
correlate with an automotive plant. The overspray
standards selected  were light overspray  (which
would be typical of paint overspray on most booth
walls and windows), moderate overspray (repre-
sentative of the robot cabinets and surfaces direct-
ly behind painting stations), and thick and heavy
oversprays (found on grates and the center track
of the booth).
    Initial paint stripping tests were conducted to
quantify the effectiveness of different types of
strippers currently being used in the industry. One
parameter specifically explored was the Impact of
paint stripper viscosity on usage rate. Since many
plants are using line purge solvent blends or non-
viscous paint strippers to  clean the booths,  a
comparison was made between a viscous stripper
and a nonvlscous stripper.
    A Nalco  paint stripper  was selected as the
viscous stripper. This  product  is a thlxotropic
material having a viscosity of approximately 20 cps
at high shear (spraying conditions) and ap-
proximately 600 cps at low shear (vertical sagging
conditions). These ranges are compatible with ease
of pumping and optimum paint stripping activity
on vertical surfaces.
    For the nonviscous stripper, a simple blend
using the same solvents as those In the  viscous
product was selected. With the same solvent pack-
age In both products, the effect of viscosity could
be studied.
    Results of these tests showed that substantial-
ly more of the nonvlscous stripper was required to
remove the  paint overspray than was the case
using the viscous stripper. The usage rate was
typically 10 to 20 times higher with the nonviscous
stripper on each degree of overspray. Thus, those
plants  using a nonvlscous stripper could achieve
a major reduction In  VOC emissions usage by
switching to a viscous paint stripper.
Nalco VOC Minimization

Further research Indicated that the application of
a water-rinsable booth masking with a viscous
paint stripper would also provide a substantial
reduction In VOC emissions. With the  masking
providing a protective barrier coating between the
paint and the booth substrate, no paint stripper
was required on light overspray areas. The over-
spray and masking could be easily rinsed off with
Just water. On moderate overspray, stripper usage
was reduced by more than 50 percent.
    With this degree of overspray, a small volume
of stripper was necessary to perforate the paint
film to allow the water to reach and dissolve the
water-soluble protective masking underneath. As

                                                                      Reducing Risk In Paint Stripping
would be expected, a lesser reduction in stripper
usage was observed on heavy and thick over-
   A VOC Minimization Program was then
developed, based on this Information, to help
automotive plants meet their restrictive VOC emis-
sion limits. By eliminating the use of stripper on
light overspray areas and reducing the amount
used on moderate overspray areas by more than
half, an automotive plant could significantly
reduce its VOC contribution from its booth main-
   Another major benefit with the VOC Minimiza-
tion Program is improved booth cleanliness. Typi-
cally, with any type of paint stripper, a noticeable
residue accumulates on the booth surfaces after
one or two weeks. This residue Is  from the inor-
ganic pigments in the paint, which cannot be
dissolved  by  the paint  stripper and which are
precipitated out onto  the booth  surface. This
phenomena can be shown through examination of
a steel  substrate after repeated applications of
paint and paint stripper with a scanning electron
microscope (SEM).
   When a masking is employed, the booth sub-
strate remains clean, with no build-up of pigment.
Various maskings can be used to protect all sur-
faces, Including windows and hoses. After 10 ap-
plications of paint and paint stripper, the steel
remained as clean as at the beginning of the test.
No inorganic  residue was detected by the SEM
   The maintenance process Involves applying
the masking to a clean booth before production
and allowing 15 to 60 minutes for it to dry. After
the production shift ends,  the maintenance
department applies a controlled amount of paint
stripper to the heavier overspray areas. After a 15
to 30 minute contact time, the stripper, dissolved
paint, and masking are rinsed off with water. The
final step is the reapplicatlon of the masking.


The potential benefits of this VOC  minimization
program include (1) VOC  emission reduction, (2)
Improved booth cleanliness /reduced dirt-in-paint
potential, (3) reduced contribution to waste water
discharge TTO limits. (4) reduced solvent exposure
for workers, and (5) total program cost reduction.
   In comparison to obsolete methylene chloride
products or alternative solvent formulations alone,
this new approach offers  significant advances in
overall performance and worker  safety. Further
research should continue  to  provide improve-
ments in both categories.

 Cryogenic  Paint Stripping
 Ashok N. Mathur
 Applied Research and Development
 Air Products and Chemicals, Inc.
 Allentown, Pennsylvania
        Cryogenic paint  stripping is a new.
        patented  method of removing built-up
        paints or coatings from hooks and fix-
 tures normally found on the paint production line.
 The hook (or fixture) is put in a cabinet where It is
 frozen and embrittled with liquid nitrogen. It is
 then impacted with high-speed nonabrasive plas-
 tic pellets that fracture the coating and debond It
 from the substrate. The process, which takes ad-
 vantage of extreme cold Instead of heat or chemi-
 cals to remove  coatings,  is quick, simple,  and
 produces no hazardous waste.
Traditional Paint Stripping

Traditional methods of paint stripping such as
solvents, hot caustic,  pyrolysis, direct burnoff,
incineration, and molten salt use heat or chemi-
cals. These processes  have  one or more disad-
vantages. Methods that use heat can

    • Weaken, anneal,  and eventually destroy
     steel components,

    • Weaken welds,

    • Detrimentally affect magnets, and

    • Cause fires, explosions, and air pollution.

High temperature also precludes use of aluminum
and other low melting point materials.
   Likewise, methods that  use chemicals can
   • Severe hazardous waste disposal

   • Reactions that cause explosions, and

   • Hazardous fumes.
These methods are also Incompatible with some
metals. Lastly, workers must wear cumbersome
personal protection equipment.
Cryogenic Paint Stripping

Cryogenic paint stripping uses liquid nitrogen as
the refrigerant to produce  the low temperatures
required for the process. Nitrogen Is Inert, color-
less, odorless, and noncorroslve; It will not burn
or support combustion.
    Air Is a mixture of 78 percent nitrogen and 21
percent oxygen. Liquid nitrogen Is obtained by
compressing and cooling air until it condenses to
a liquid that Is then distilled into Its components.
Liquid  nitrogen  has a boiling temperature of
-320°F at atmospheric pressure.  During the
cryogenic paint stripping process, liquid nitrogen
vaporizes to nitrogen gas that Is returned to the
    The coated fixtures are cooled with liquid
nitrogen In a specially designed cryogenic cabinet.
As cooling progresses, the coating becomes brittle
and contracts (shrinks) around the fixture. Be-
cause the coating shrinkage is greater than that of
the fixture, tensile stresses develop, producing a
brittle, highly stressed surface.
    While in this state, the fixture Is struck by high
velocity, nonabrasive polycarbonate pellets that
crack the coating and debond It from the sub-
strate. The result Is clean fixtures that do not need
additional washing.

The Equipment

All parts to be stripped are placed onto a loading
tree and then mechanically lifted onto a spindle at
the top of the cabinet. This spindle rotates the

                                                                       Reducing Risk In Paint Stripping
loading tree in front of the throwing  wheels
throughout the cycle.
    Hooks are cooled by liquid nitrogen until the
coating becomes embrittled and then are struck
by high velocity media from the throwing wheels.
The mixture of media and paint chips is collected
at the cabinet bottom and conveyed to a two-deck
separator that classifies it Into oversized and un-
dersized chips and media (the pellets). The paint
chips are collected as compact solid waste and can
be  disposed of  economically.  The media is
reclaimed and conveyed back to the throwing
wheels, and the nitrogen exhaust gas is cleaned of
paint dust before being ducted  to  the outside
    The cabinet and components have been care-
fully designed and constructed for low tempera-
tures. A panel contains controls to operate  and
optimize  the process. Interlocks have been  in-
tegrated to ensure operator safety.
    The equipment is illustrated in Figure 1.

Performance Capabilities

Alkyd, acrylic, polyester, vinyl, and lacquer coating
have  been successfully removed from various
parts. Because epoxy and urethane coatings are
harder to remove, satisfactory results are not al-
ways obtained. Coating thickness should be be-
tween .010 of an inch  and .500 of an inch for best
results; coatings of less than .010 of an inch are
more difficult to remove.
    Loads are limited to 400 pounds of parts per
cycle. Cycle times vary between 5 and 15 minutes,
with an average cycle of 10 minutes. Best results
are obtained when the parts are loaded so as to
expose them to the media blast. However, because
the media inside the cabinet rebounds several
times,  even recesses and shaded  surfaces  are
cleaned well. Round hooks are stripped effectively
even though they are touching adjacent hooks on
both sides.
Process Safety

Basically safe, cryogenic paint stripping does not

    • Fume, smoke, or pollute.

    • Produce hazardous wastes and
      subsequent disposal problems, and

    • Explode or cause fires.

    Two safety issues connected with cryogenic
paint stripping are

    • Preventing oxygen deficiency by ducting
      the exhaust gas outside the building, and

    • Protecting workers against the extremely
      cold process temperatures by requiring

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                                                                            13. KOIt INJECTION I WE
                                                                            U. lEIDfUlE IOTTH CUTE
                                                                            15. KOII S1EEP IEUMTOI
Rgure 1.—The CRYO-STRIP* cryogenic coating removal system.

     the wearing of gloves during unloading.
     Cold parts warm quickly and can usually
     be handled with bare hands within five
Economics of the Process

The economics of cryogenic paint stripping
depends on the individual customer's operation
and requirements. This process is particularly
economic when

    • Production requirements are high,

    • High costs are incurred from disposal of
      hazardous wastes, and

    • Heat and chemicals will damage the hooks
      or fixtures.

    Additional savings can be realized from these
other aspects of the process:
   • Fixtures do not need to be cleaned or
     washed after cryogenic stripping.

   • Fixtures are usually not damaged by the
     stripping process.

   • Fire or explosion hazards are eliminated
     from the process.

   • Worker safety insurance costs are

Cryogenic paint stripping offers a viable alterna-
tive to more traditional methods. Although perfor-
mance guidelines are supplied, only testing can
determine the process's success for a given coating
on a particular part. Air Products and Chemicals
maintains a laboratory and a production scale
CRYO-STRIP® machine to test customer parts for

Use of Plastic  Media  Stripping in  Original
Equipment  Manufacturers' Applications
Joseph E. Konopka
U.S. Technology Corporation
Dante/son, Connecticut
          While there has been much publicity
          about the use of granulated plastic
          media for aircraft maintenance strip-
ping, not much has been published about the use
of  this  process  in  original  equipment
manufacturers' (OEM) applications. Yet, there has
been substantial growth In industrial applications
since 1978, the year that granulated plastic media
was Introduced. This presentation will describe
and assess the use of plastic media stripping for
reflnlshing new or warranteed OEM parts and
Plastic Media Blasting

Equipment parts or finished products may be
rejected by quality control standards because of
errors in painting. Such flaws may be only cos-
metic, while others present potential failure in
corrosion protection systems or in meeting color
specifications. It is common practice to attempt
spot repairs or to ship large quantities of such
rejects to obscure chemical strip shops. Fixtures
used to transport parts on paint lines are also sent
out to chemical stripping or bake-off facilities to
remove thick paint buildup.
    Plastic media blasting offers the generators of
paint rejects or coated fixtures an acceptable al-
ternative to methylene chloride and other toxic
strippers. Many production paint operators or
their contract strippers have begun using plastic
abrasives in relatively inexpensive direct pressure
blast systems to complement their exlstingproces-
ses. Also, a growing number of dedicated "dry
stripping" facilities have begun operating around
the United States and Canada to provide plastic
media stripping services to  Industry and
automobile refurbishers. Many such operations
are trained and certified to perform plastic media
   A wide variety of OEM components and
products are being stripped with plastic media
today. These range from brass water faucets to
zinc die cast automobile mirror housings, to thin
gauge steel cabinets for room heaters, to glass
headlight lenses on automobiles. Generally, any
component or product with significant manufac-
turing costs can be economically stripped by plas-
tic media blasting.
   Plastic media can effectively strip tough coat-
ing  systems applied by E-coat or powder coat
methods, as well as very tough chemical agent
resistant coatings (CARC) from military vehicles.
There are very few coating systems so tough that
plastic media cannot effectively remove them.
Advantages of Plastic
Media Blasting

There are  many advantages to using plastic
abrasives in industrial stripping activities. These

    • The plastic media is highly reusable and
     easily reclaimed.

    • There Is reduced danger to workers and

    • This Is a dry process with reduced waste
     volume and disposal costs.

    • The plastic is neutral in pH level, inert,
     and noncorrosive.

    • The media will not embed In most

    • Anodlzed, galvanized, phosphated, or clad
      coatings can be retained undamaged.

    • Composite stripping Is faster and safer
      than any alternative method.

    • There is no metal embrlttlement danger.

    • There is no pitting to many metals,
      including die cast zinc, cast magnesium,
      aluminum, or brass.

    • The process Is faster than chemicals in
      many applications.

    • There are no capillary entrapment

    • Plastic stripping often eliminates the need
      for disassembly of component parts.

    • There are lower equipment maintenance
      costs than for hard grit blasting.

    • The process preserves tolerances on
      delicate parts.

    • There Is no flash rusting on stripped
      parts, reducing the urgency to recoat.
The Plastic Media Blasting

While there are many types of plastic resins, only
a few are effective as paint strippers. There are
currently seven different granulated plastic media
types available in  the marketplace, although
blends of these unique plastic types are also sold
and used in limited applications. These can be
propelled In airblast  systems,  similar to
sandblasters,  or in  airless systems  using
centrifugal wheels to propel media. Most stripping
with plastic media Is performed manually, either
in hand cabinets or In open blasting. Typical blast
pressures range from 20 psi to 60 psi. In airless
systems, wheel speed may be as  high as 14,000
    All of the plastic media types are reusable,
although durability, as well as stripping capability,
varies from one type to another.  Strip rates are
greatly affected by variables like paint resiliency,
paint bond, blast pressure, angle of impingement,
size of the plastic granules, and distance from the
work piece. Therefore,  strip  rates can be most
reasonably described In a range, as shown in Table
1. The times shown are for 1/4"  ID blast nozzle
(which is the smallest typically used) and a direct
pressure air blast system. Siphon-feed systems
are  not recommended for high-production strip-
 ping with plastic media. The media types listed are
 those recognized in U.S. Military specification Mil-

 Table 1.—Plastic media strip rates (1/4" ID nozzle, dl-
 rect pressure blast).
(SO. FT./MIN.)
.05- .28
.3 -1.5
.6 -1.8
.5 -1.3
.15- .75
    Of course, consumption of the plastic media is
 another major consideration. The plastic abrasives
 are reusable through several blast cycles. While
 figures are available for consumption per blast
 cycle for each of the types of plastic abrasive, these
 are not very meaningful, because the time It takes
 to strip a coating will dictate consumption per
 operating hour, per part, or per square area. Table
 2 indicates the average consumption per nozzle
 blast hour, assuming a 1/4" ID nozzle in a direct
 pressure  blast system. Usage at two pressure
 levels are also shown.

 Table 2.—Plastic media consumption per nozzle hour.
             AT 25 PSI           AT 50 PSI
 MEDIA TYPE     (IN LBS.)           (IN LBS.)
20 (most blasting at 50 psi)
24 (most blasting 25-40 psi)
32 (most blasting 25-40 psi)
30 (most blasting 25-40 psi)
8 (most blasting 40-60 psi)
30 (most blasting 20-30 psi)
 Costs of Plastic Media Stripping

 While consumption analyzed by operating hour
 can be useful In predicting costs, the paint coating
 itself dictates the efficiency of the process. There-
 fore, Table 3 identifies ranges of consumption per
 square foot of stripped area for each of the popular
 media types. These data are based on typical strip
 rates as shown in Table 1.

Table 3.—Media consumption range per square foot.
                       PLASTIC MEDIA CONSUMPTION
MEDIA TYPE                       (IN LBS.)
1.2 -6.6
 .25- .6
 .35- .66
 .35- .6
 .2 - .3
 .4 - .9

                                                                         Reducing Risk In Paint Stripping
    Based on Table 3, it appears that it would not
be efficient to ever use Type I, or that only Type V
should be used given its excellent durability. How-
ever, the individual physical characteristics of the
media types—especially hardness and specific
gravity—are essential for such special finish re-
quirements as maximum surface profile on soft
materials,  no degradation of soft materials like
composites, and minimizing peening effects on
thin sheet metal  like  aircraft skins. The faster
stripping plastic types may be too aggressive to
meet certain finishing goals. On the other hand,
for more durable parts made of anodlzed cast
aluminum or phosphated  sheet steel, the more
aggressive Types II or in provide much greater strip
rates without degrading the substrate or corrosion
protective coating, thus reducing overall process
    Blast and reclaim equipment should be care-
fully selected to ensure efficient operation and
maximization of the potential savings of plastic
media stripping. The blast equipment should be
capable  of propelling the plastic media without
sputtering or erratic flow. An adjustable media
flow valve should be included. The recycling media
must be cleaned  by removing dust  (which can
severely reduce the strip rate  by acting as a buffer)
and removing large contaminants like paint flakes
or metal shrapnel. Magnetic traps are also strongly
advised. Ventilation in standard blast cabinets is
                              adequate for removing airborne dust to maintain
                                 Disposal of the paint and plastic dust residue
                              is a concern in that, although the plastic dust itself
                              is inert, toxic elements from the paint itself may
                              cause the residue to be considered hazardous. The
                              cost of disposing of this dry waste is much less
                              than wet waste but varies from region to region.
                              Overall, the volume of waste is much smaller than
                              for solvent stripping operations and wastewater is
                              not generated.
                                 The U.S. Navy compiled  some comparative
                              figures on process costs for both chemical strip-
                              ping and plastic media  stripping of aircraft. The
                              figures shown in Tables 4 and 5 reveal an overall
                              cost reduction of 48 percent compared to chemical
                                 Industrial examples of this kind are harder to
                              obtain,  but the Increasing use of plastic media
                              blasting in industry implies economic advantages,
                              particularly when  waste disposal costs  are fac-
                              tored  In. One of the major advantages of plastic
                              media stripping is that  subsequent paint rejects
                              on plastic media stripped parts are no higher than
                              normal, whereas  chemically  stripped parts  or
                              spot-sanded parts may have higher failure rates.
                              The cost analysis for operation of an industrial dry
                              stripping facility is shown  in Appendix A, and a
                              model cost worksheet is shown in Appendix B.
Table 4.—Summary table of chemical stripping costs.
 Source: Naval Civil Engineering Laboratory, "Economic Analysis for Recycling Plastic Media" (CR 87.001), February 1987.
Water usage

Water treatment

Hazardous waste

468 gallons
364 hours
200,000 gallons

200,000 gallons

1 ,024 pounds

$0.43 per 1,000
$8.24 per 1,000

$ 5,335
$ 86

$ 1,648

$ 102
$ 333
$ 667
$ 1.347
$ 800,000
$ 12,900

$ 247,200

$ 15,360
$ 50,000
$ 100,000
$ 202,000
 Table 5.—Summary of plastic media blasting costs.
Plastic Media
Non-PMB Stripping Costs
Hazardous Waste
Paint Dust
Spent Media

1 ,500 pounds

183 hours

200 pounds
1 ,500 pounds

$1 .76/pound



$ 2,640
$ 667
$ 8,235

$ 26
$ 195
$ 173
$ 1,333
$ 	 47
$ 396,000
$ 100,000

$ 3,900
$ 29,250
$ 26,000
$ 200,000
$ 7,000
 Source: Naval Civil Engineering Laboratory, "Engineering Analysis for Recycling Plastic Media" (CR 87.001), February 1987.

Conclusion                                 should be on overall process cost savings available
                                                 through plastic media stripping compared to alter-
Plastlc media stripping offers Industry a low-cost     naUve technologies. But the added Intangible
method of reclaiming valuable components and     value8 of ^creased worker and  environmental
finished products, as well as an important alter-     «** "** *»* striPPmg me&od should also not
native in overhaul and rebuild  activities. Focus     **" overlooked-

                                                               Reducing Risk In Paint Stripping
                                APPENDIX A
                Analysis for Investment in a Dry Stripping Facility
Cost Category                           Start UP
Start up costs
    Blast/reclaim system (1/2" nozzle)   $19,000
    Compressor/dryer (50hp)              14,000
    Dust Collection (fans & filters)       2,000
    Blast room  (16Hxl8Wx40L) home built  5,000
    Installation                          2,000
    Furnishings                           2,000
    Rent Deposit (3 months)               3,600
    Initial media l,5001bs 9 $2.00/lb     3,000
    Two months working capital           14,393
                  Total investment      $64,993

Operating Expenses (Fixed)
    Loan payment ($60,000 pay back in 5 yrs ®13%/yr)
    Rent   $l,200/month
    Labor (2 people 9 $10.00/hour)
    Heat & lights  ($200/month)
    Phone & office supplies  (250/month)
        Yearly Operating Expenses

    35 Ibs. media/car 9 $2.00/lb.
    masking materials
Utilities  (used when dry stripping)
Waste disposal  ($125 for 55gal = approx. 8 cars)
Total Variable Costs

                               Breakeven Calculation
Fixed Costs
Variable Costs
Average charge/car of $350 minus $115.63/car equals $234.37  contribution/car.
Breakeven = fixed costs/contribution = $86,982/$234.37 = 371.13  cars/year.
(Based on a $100/hour blast charge this would translate into 26  blast  hours  per week
for a breakeven).
Capacity for two man, one shift shop is two cars per day;  equals 10  cars  per week
Profit before taxes for one shift
         10 - 7.13 = 2.87 cars x $234.37 = $672.64/week x 50 = $33,632/year

While the above figures are realistic for setting up a dry stripping facility,  they
are only one example.  Start-up costs can be reduced by buying used  equipment.
While operating costs can vary considerably based on labor rates, higher  or  lover
loan payments, and rent expense.  If there is room for a facility in a currently
used building, with labor that could be used for either business, then a  breakeven
point can be as low as 3 cars or 11 blast hours per week.   Similarly,  charging  $50
more per car lowers the breakeven point by one car per week.

                     APPENDIX B
Process Gosf Analysis
Process Item
Labor for Preparation
Labor for Stripping / Cleaning
Labor for Follow-up Cleaning
Labor for Pre-Finishing
Compressed Air
Other Utility Costs
Insurance/Liability Costs
Example: Lost Income
Equipment Maintenance
Disposal of Waste
Material Usage (Total Process)
Subsequent Failures
Example: Corrosion of paint
Miscellaneous "Down-Time"
Minimum Parts Inventory
NOTE: Because plastic media stripping has been shown
to reduce down-time in overhauling many types
of vehicle parts and components, the number
required in inventory can be reduced, reducing
capital expenditures.
.$ •'•"/' '. .•-.''•
.l;.;; •'., . '•
$ .
$ "
.$ . . .. ..:.
i:v ".'•
.-$- :, . :,:-.,,
$.?. :'.'..:"
$ .••' .
> Risk to workers
> Risk to environment
»• Miscellaneous liability
» Worker morale
* Customer satisfaction
> Community relations

Ultra  High-pressure Water for  Paint
Removal in the  Original  Equipment
Manufacturing Sector
Al Hlrsch
Flow International
Kent, Washington
New restrictions on the use of paint removers
containing methylene chloride mandated under
the 1990 amendments to the Clean Air Act are
forcing manufacturers In the original equipment
sector to explore alternative methods for removing
paint from metallic surfaces. Some of the new
techniques Involve less toxic solvents, acid, sand
blasting, and application of heat.
   The use of ultra high-pressure water to remove
hard, tough coatings from metallic substrates
without damaging the surface is one of the more
effective new paint removal processes. Given the
present concern for the environment and need to
keep costs down, there are a number of reasons
why ultra high-pressure water Is becoming the
"tool of choice" In many material removing/strip-
ping tasks:

   • Low volume of effluent: A relatively low
     amount of water Is required  vis a vis the
     volume of material to be removed.

   • Easy  separation of material: In most
     cases, simple settling tanks  will separate
     the water from the paint or other substance
     removed; the water can then be disposed of
     through the public  sewage treatment

   • No toxic or hazardous wastes: The process
     produces no toxic, hazardous, or flammable
     substances that require special handling.
   • No sand and/or dust:  Sand blasting
     requires large volumes of material to be
     disposed of,  particularly  where used on
     modern paint systems. Also, it Is difficult to
     separate the sand from the  material
     removed, and airborne dust and silt can
     block waterways.

   • Low energy costs: Ultra high-pressure
     water does not require large energy costs
     (gas or electric) or extensive maintenance.

   The process involves a stream of water pres-
surized to 35,000 psl for hand-held applications,
or 55,000 psl if robotics are  used. The paint is
removed  via energy generated  by the stream,
which moves at a  rate of 2,280-2,860 feet per
second.  The technology can accurately be
described as the "razor blade" of the water-blasting
The following pieces of equipment are necessary
for the process:

   • Pump:   The   process   uses   an
     Intenslfier-based pumping system that
     converts mechanical energy Into oil
     hydraulic energy  Into water  hydraulic
     energy, i.e., ultra high-pressure water.
     Diesel   or  electric-driven   Jetpacs
     manufactured by Flow International deliver
     .8 to 5.6 gpm of water at 35,000 psl.

      Hose:  The required hose has  an inside
      diameter of 4 mm. with a working pressure
      of 35,000  psi  and a burst  pressure of
      100,000 psi.

      Tools: Tools can  be hand-held devices
      called Jetlances, which are equipped with
      rotating, multiple Jet tips; alternatively,
      mechanized devices designed for robotic
      integration can be used.

 One of the most Important applications of the ultra
 high-pressure water blasting method is the clean-
 ing of car carriers that are coated with multiple
 layers of polyurethane paint. If not removed, layers
 build up, flake off, and attach themselves to fresh
 paint on car bodies, causing costly damage. Cur-
 rent methods of removal Include low-pressure,
 high-volume water blasting, gas or electric ovens,
 solvent baths, and hand chipping.  Ultra high-
 pressure water is currently being used as an alter-
 native in seven General Motors and 10 Korean car
    Another application Is the removal of modern
 polyurethane  or epoxy-based hull  paints from
 ships. This technique has also  been used to
 remove contaminated paint and  thin layers of
 concrete In nuclear facilities, hard rubber lining
 from storage tanks and  metal rollers, hard
 deposits from boiler and heat exchanger tubes.
 and ceramic and base coats from jet engine com-
 ponents that  currently require  sand blasting,
 acids, and solvents.
 Potential  Hazards

 Water poses few of the safety and environmental
 hazards found In other solvents and cleaners. It is
 "Inert," a known  quantity, and can be easily
 separated from toxic or nontoxlc solids  after
 removal. However, training operators for safe ap-
 plication Is Important since ultra high-pressure
 water removal cuts like a razor, due  to its low
 thrust as a result of the low volume of water.

The "harder" the coating the more effective ultra
high-power water will be in removing It, provided
the substrate can handle the high-energy density
of the water Jets. The process is effective on some
ceramic coating, epoxles, polyurethanes, lacquers,
flame and plasma sprayed metals, some fusion
bonded coatings,  and hard rubber. Soft, tacky.
Jelly-like coatings do not lend  themselves to
removal with ultra high-pressure water. However,
low-pressure, high-volume water blasting can be
an effective stripping method with these products.
    Steel and equivalent substrates pose  no
problems with the ultra high-pressure water sys-
tem. For aluminum, pressure, stand-off distance,
and Jet dwell time become critical because the
ultra high-pressure water  system does have the
energy  density to remove that metal, thereby
damaging the substrate. Ultra high-pressure fan
Jets can be an effective stripping method provided
no  hot spots  are  present In the fan. In general,
ultra high-pressure water  is not appropriate for
use on wood, plastic, and composite  substrates
because the high-energy density will attack these
Stripping Time

It Is difficult to estimate stripping time exactly
because of variables such as flow rate, pressure,
number and rotation speed of Jets, Jet configura-
tion, dwell time, stand-off distance, thickness of
material, and operator proficiency.
    Approximate estimates are as follows:

    • Polyurethane-based paint on steel
      substrate. 5-10 mils thick: 100-120
      sq.ft./hr. using 2.8 gpm ultra
      high-pressure water at 35,000 psi.

    • Polyurethane-based paint on steel
      substrate. 15-20 mils thick: 30-100 sq.
      ft/hr. using 2.8 gpm ultra high-pressure
      water at 35,000 psi.

    • Arcor S30, 50-250 mils thick, on steel
      substrate: 120 sq. ft./hr. using 2.8 gpm at
      35,000 psi.

    • Commercial paint removal from concrete
      substrate: 50-80 sq. ft./hr. using 2.8 gpm
      at 35,000 psi.

The capital costs for a Flow International ultra
high-pressure water system are:

   • Pump: (Model  40EDX, 75 HP, electric
      driven, 2.4 gpm at 35.000 psi): $76,500.

   • Hose: (50 ft., 35,000 psi working pressure,
      100,000 psi burst pressure): $1,325.

                                                                    Reducing Risk In Paint Stripping
U Tool: (Model 5050 Jetlance): $7,800.
• Total: $85.625
Operating costs are:
• Pump: $4 to $5 per hr.
• Hose: $2 per hr.
• Jetlance: $2 per hr.
    • Total: $8 to $9 per hour.
    Costs for water, electricity, waste disposal, and
labor are not Included.
    The ultra high-pressure water system Is clear-
ly a cost-effective, viable approach to paint removal
that can replace methylene chloride compounds
presently used for  these  tasks in a variety of

   Exposure Control &
   Pollution Prevention
        Chair: Christine Whittaker
       Office of Risk Reduction Technology
         Health Standards Division
    U.S. Occupational Safety and Health Administration

Practical  VOC Reduction
Thaddeus J. Fortin
Haas Corporation
Philadelphia, Pennsylvania

Reducing volatile organic compounds (VOC) Is a
concern of every company that paints. Amend-
ments to the Clean Air Act are forcing companies
to change their processes to  accommodate VOC
reduction. Practical VOC reduction In paint shop
maintenance  Is attainable  without incurring
added costs.
   There are  many economical ways to reduce
VOC emissions from maintenance without making
major changes to the painting process. Reduction
In the volume of solvent-based stripper used, sub-
stitution of nonsolvent chemical products to
replace  stripper, nonchemical substitutions of
stripper, and mechanical substitution for stripper
are four practical ways to reduce VOC emissions
without sacrificing quality, costs, or manpower. A
brief explanation of each method follows.

    • Immediate VOC reduction of 25 to 75
    • replace flammable product with
      combustible product
    • reduce worker exposure
    • reduce chemical usage, storage, and

    • rlnsable with water vs. wipe on/wipe off

    • significant cost savings in labor,
      chemical, and auxiliary products


    • change in maintenance process
Figure 1.—Thlxotroplc strippers.
 Volume Reduction

The most immediate and obvious way to reduce
VOC emissions in maintenance is to simply reduce
the amount of stripper used. Many original equip-
ment  manufacturing (OEM) companies are still
using low-viscosity strippers such as paint thin-
ner, purge cleaners, and solvent blends. These
products usually contain high amounts of flam-
mable chemicals such as methyl ethyl ketone and
toluene/xylene. The use of thlxotropic paint strip-
pers,  which are usually combustible, offer and
immediate and significant VOC reduction. The
lower evaporation rate of these products, com-
bined with the ability to cling to a surface and work
over a period of time, can result In VOC reductions
of 25 to 75 percent.
Water-based Products

Thlxotropic strippers can effectively reduce VOC
emissions caused by solvent cleaning. The use of
water-based protective products in this applica-
tion  can all but eliminate VOC. Water-based
products can be used in conjunction with strip-
pers or as a complete substitute.
   In small spray booths or booths with small-
volume waterfall  systems, water-based peelable
coatings can be applied to walls, windows, and
equipment. These products are available In white
or clear and, because they are water based, they
do not have a flash point. Solvent-based peelables
should not be used.

    In large volume water-washing booths, steel
and glass walls can be covered with water-rlnsable
coatings as a barrier against paint overspray. Like
peelable coatings, these products are water based
and contain little If any VOC. They also have no
flash point. Water-rlnsable coatings are applied by
spray or brush and used in conjunction with
strippers In areas where heavy overspray buildup
occurs or as a substitute for solvent strippers. VOC
reduction is usually 20 to 100 percent.
    Several OEM companies spray paint stripper
on their grates to remove paint buildup. This is a
most ineffective and wasteful way to clean grates,
since these structures have very  little horizontal
surface area, hi fact, less than 25 percent of the
booth floor area is solid surface. This means that
more VOC-laden stripper Is wasted than is actual-
ly used. Another method of grate cleaning Is to
replace the painted grates with an alternate  set
and then clean the  first set by immersion into
caustic or solvents. However, an  effective water-
rlnsable grate coating is more efficient.
    Grate coatings are usually white thlxotroplc
materials, designed to cling to the grates and to
form a durable, nonchalking barrier against paint.
Good  grate coatings usually dry In  15  to  30
minutes to eliminate tracking and are removed by
mechanical high-pressure water.  Again, because
they are water-based materials, they do not con-
tain VOC and do not have a flash point.
    An emerging method of reducing VOC emis-
sions is the use of water-based, or non-VOC strip-
pers. Although still in early stages of development,
such products may offer another alternative where
strippers must be used. Solvent strippers have so
far not been superceded In all applications, but in
certain areas water-based strippers are effective.
These areas  include automotive  paint facilities
where production Is high but overspray volume is
low. These products need to be carefully formu-
lated so  as not to interfere with sensitive detack-
Iflcatlon programs.

Protective Covers

As many large OEM paint facilities are updated
with automatic spraying equipment that Is sensi-
tive to chemicals, removing the paint overspray Is
becoming quite a challenge. At first, solvents were
used to manually wipe clean the equipment, but
this process posed many problems. As  a result,
protective equipment covers were developed.
These  covers are an  attractive alternative to sol-
vent usage. Covers  completely eliminate VOC
while protecting the sensitive equipment.  They

     • reduce BOC emissions 10 to 20 percent
     • replace combustible solvents with water
     • health and safety
     • excellent rinsabillty
     • right product for the job
     • collects airborne particles
     • asthetlcally pleasing

     • change In maintenance process
     • may require additional stripper
     • paint detacklficatlon sensitivity
     • added product(s)
Figure 2.—Water-based products.

come In many sizes, materials, and designs and
can be disposable or washable. The covers last
days or even weeks, and cost savings in chemical
usage and manpower are substantial.
     • VOC reduction up to 100 percent
     • no chemical use
     • no worker exposure
     • helps paint detackiflcation
     • disposable/washable
     • equipment longevity
     • significant costs savings In labor,
       chemical, preventive maintenance,
       equipment longevity


     • change In maintenance process
Rgure 3.—Protective covers.

Mechanical Reduction

Mechanical methods of VOC reduction are also
becoming popular. This alternative requires a
capital expenditure; however, the technology is
efficient  and, In many cases, an  overall cost
savings can be achieved. From a safety point of
view, this method is often preferable to solvent dip

                                                                     Reducing Risk In Paint Stripping
tanks to strip small parts, racks, or grates. VOC
can be completely eliminated.

The amendments to the Clean Air Act and other
legislation have made VOC reduction mandatory
for even small companies to meet  compliance
regulations.  Many  economical alternative tech-
nologies are  available to help reduce VOC in the
area of paint  shop maintenance. It should be
remembered that each operation has different
cleaning requirements. Finding the best applica-
tion for a particular plant requires that all internal
and external factors be taken into consideration
before making a decision. Once a thorough plan is

     • VOC reduction up to 100 percent

     • no chemical use

     • helps paint detackification

     • possible cost savings


     • capital expenditure

     • worker safety precautions
Figure 4.—Mechanical substitutions.

Implemented, volatile organic compounds can be

 The Sponge Jet  System-
 Bill Lynn
 Sponge-Jet, Inc.
 Dover, New Hampshire

 The Sponge Jet System was designed to offer the
 market an alternative method to steam cleaning or
 hot pressure washing. The use of an absorbent
 sponge as an  alternative to dilution with large
 amounts of water to remove grease, oil. waxes, and
 other absorbable contaminants has proven very
 effective for surface cleaning from both a function-
 al and environmental standpoint.
    Since paint stripping  was not the primary
 function the Sponge Jet System was designed to
 perform, we have limited experience with this ap-
 plication. A small company with limited funds for
 research and development. Sponge-Jet. Inc., can
 only move slowly on new procedures.  Using a
 partlculate sponge as a cleaning and stripping
 media opens up a lot of possibilities—and almost
 some impossibilities. For quite a while. It seemed
 impossible to find a company with enough faith in
 our processes  to manufacture the sponge, and
 designing a system that would adequately propel
 the sponge was an extended effort. For all practical
 purposes, the Sponge Jet System produces a func-
 tional end result similar to all media blasters, but
 because this media is light and irregular, it is not
 possible to achieve flow in common equipment.

 Controlling Pollution During
 Soft Media Blasting

 Finding ways to control pollution during the paint
 stripping process offers some interesting challen-
ges to the Sponge Jet System. Using a sponge
introduces a flexibility that is not found in most of
the other accepted paint stripping media. Since we
are a new company, we haven't unraveled all the
possibilities; however, to date the Sponge Jet Sys-
tem has cleaned heavy motor oil from wallpaper
and also stripped  paint from steel, leaving an
anchored pattern.  The question is how to take
advantage of this flexibility to control pollution
while stripping paint.
    Sponge media's ability to absorb and control
various contaminants is one of its primary
strengths.  Imagine absorbing a paint spill with
pulverized cloth or common mineral absorbents!
The Sponge Jet System propels a vast number of
absorbent particles to a surface and provides great
amounts of surface to absorb contaminants. If this
system is used in conjunction with chemical strip-
pers or  softeners,  amounts  of liquid waste are
greatly reduced. The sponge removes and controls
both the stripping chemical  and  the dissolved
paint in a dry operation.
    Containing dissolved paint and stripping
chemicals In an absorbent media is a neat trick
but. for pollution control, only a step In the right
direction. Separation  of contaminants from the
media is of paramount Importance in reducing the
waste stream. Most sponge media react to flushing
much like a common hand sponge; however, the
Sponge  Jet System  provides a  closed rinse
centrifuge system for flushing sponges. With this
process, we have reduced hydrocarbons from 30
percent to less than 2 percent.
    Sponge media has also removed paint without
chemical assistance. Because it Is manufactured,
the sponge can be made to varying degrees of
hardness. The sponge matrix will also hold many
of the common abrasives and allow for repeated,
dustless blasting at production rates somewhat
slower than if the abrasives were virgin.  This

                                                                      Reducing Risk In Paint Stripping
ability to trap abrasives In a media that can be
washed may  have environmental advantages
during paint stripping operations.
   The absorbent nature of the sponge allows It
to carry other materials to the surface. With plastic
media, dust generated by the operation is greatly
reduced by using a damp  sponge as part of the
media mix. It may  also be possible to use damp
sponges to clean the surface of plastic  media
before it is recycled.
   To control dust during blasting, we have mixed
damp sponge with bicarbonate. Currently, a major
mineral company Is working with us on a natural
mineral abrasive  that, In  combination with
sponge, will strip paint and remove grease and oils
in one system. Other chemicals can be added to
the sponge, Including neutralizes to reduce pH
readings on surfaces that  have been chemically
stripped and substances to dissolve salts (present
on many surfaces)  that are mixed with abrasives
to achieve one-step surface preparation and salt
   Additional applications for soft media blasting
could Include:

   • Reducing fumes from chemical strippers.
      If strippers with an  affinity for soft media
      can be  formulated,  the sponge could be
      used at very low pressures to  form an
      absorbent barrier during the working cycle
      of the  chemical, which then could be
      removed by a higher-pressure blast.

   • Digesting blasting  media. Sponge media
      might prove  to be ideal for  this technique
      since it could be readily salted with material
      to Induce bacteria to feed upon It.
      Absorbing lubricants. Damp sponge that is
      frozen with carbon  dioxide become more
      aggressive to surfaces and could be used to
      absorb grease and  oils, presently moved
      from one surface to another through dry ice

      Separating contaminants from media.
      Sponge  has a  unique  ability to change
      particle  size. Fluids cause them to swell;
      conversely,  introduction of a vacuum will
      compact them.  These characteristics may
      prove useful In separating paint and other
      toxics from media.

The Sponge Jet System could be a positive environ-
mental tool to use in paint stripping. Its flexibility
makes It a possible player in combination with
chemicals and other media; its ability to absorb
and control contaminants and flush them easily
holds much promise; and its ability to carry to the
surface a wide array of impregnated liquids could
prove useful. Finally, It Is now possible to engineer
a more abrasive sponge.
    Sponge Jetting Is the new kid on the block,
waiting to find where it belongs in the paint strip-
ping industry. Enterprising minds hopefully will
take advantage of its unique capabilities and pro-
vide the industry with another tool to bring paint
stripping functions and environmental controls
closer together.
    We at Sponge-Jet,  Inc.,  welcome  any ideas
from or Joint efforts with the more experienced,
knowledgeable players in the industry.

 Recycling Methylene  Chloride:
 Optimizing the Waste  Stream
 Peter R. Morton
 Romic Chemical Corporation
 East Palo Alto, California

 There is a definite and well-defined movement
 toward  hazardous waste minimization. The
 Federal government has made a conspicuous and
 well publicized commitment to reduce pollution,
 and a process has been established to ensure that
 Industry will maintain a healthy and clean en-
 vironment. Industry must now respond by reduc-
 ing hazardous waste or face legislation that
 imposes stiff fines, felony jail sentences and, in the
 process, negative publicity on the violators.
    In the face of this potentially adversarial
 relationship,  some companies are reaching for
 positive change and implementing successful
 waste minimization  programs.  Under such
 acronyms as WRAP  (Waste Reduction  Always
 Pays—DOW  Chemical Company) and SMART
 (Save Money and Reduce Toxics—Chevron Cor-
 poration), these and other programs have repor-
 tedly realized a better than 80 percent reduction
 in solvent acquisition and  a maximum  of 135
 percent return on their investment. Indeed, Romlc
 Chemical Corporation also Instituted an  award-
 winning conservation program.
   These conservation programs demonstrate in-
 vestments in new equipment generate savings in
 disposal costs and acquisition of virgin solvents
 that often pay back investments in less  than a
year. This is a challenge to the supposition that
company profits and federal legislation conflict.
Arguably, only larger companies can profitably
invest in expensive recycling equipment. However.
the smaller firms can benefit from the methods
used to support these procurements.
 Waste Minimization Strategies
 There is no single method for reducing wastes—no
 magic bullet, black box, or mystical additive. Ef-
 fective waste minimization programs begin with a
 comprehensive understanding of the manufactur-
 ing process: its limitations and tolerances, the
 waste produced, and its composition and proper-
 ties. Only after the analysis is completed and
 compared to current waste disposal alternatives
 will industry realize meaningful options.
    The solution is often as complex and multidis-
 clpllnary as it is simple. Waste minimization re-
 quires concerted effort from top management to
 the basic employee, who  is the vehicle  for any
 conservation policy. However, the best plans use
 a coordinated effort that Involves the engineering,
 production,  maintenance, environmental, and
 analytical departments. To conserve resources,
 the informed industrial company will use the fol-
 lowing waste handling hierarchy:

    • Source reduction,

    • Reclamation,

    • Reuse, and

    • Disposal.
Source Reduction

The ultimate goal of source reduction is to produce
less waste. This is accomplished through

   • Process modifications.

                                                                      Reducing Risk In Paint Stripping
    • Efficient use of cleanup solvents, and

    • Solvent substitution.

    Industry can achieve reductions by modifying
manufacturing  processes to use solvents more
effectively or by cleaning process equipment less
frequently.  By defining what  "clean" equipment
means, a company can determine how much sol-
vent does the Job and order cleaning events to use
solvent efficiently.
    Another way to reduce waste is to change to a
more effective solvent. New limits on VOC emis-
sions and other legislation have forced reevalua-
tlon of many solvent processes and resulted in
solvent substitutions. Regulation-motivated sub-
stitution may not reduce wastes; however, it can
reduce total toxic organic emissions.
    Some alternatives were explored in an EPA
report, "Evaluation of Alternatives to Toxic Organic
Paint  Strippers," by  W.J.  Hahn and P.O.
Werschulz (EPA/600/S2-86/063,  September
1986).  This study compared and contrasted  the
effectiveness  of various commercially available
paint stripper formulations that could lower total
toxic organic emissions. The results confirmed
that,  under certain  conditions,  methylene
chloride-free  strippers could be used. Another
benefit not mentioned by the authors is potential
reduction of incinerable wastes. For example, the
substitution of a combustible solvent (such as
toluene, isopropanol, or N-methyl pyrrolidone) for
methylene chloride frequently alleviates any need
for incineration.  Additionally,  the reclamation
potential of methylene chloride is  not affected
when the cosolvent Is carefully chosen.


The intent of the Resource Conservation and
Recovery Act is to reduce waste and encourage
recycling. Recycling has several benefits: it mini-
mizes wastes requiring disposal, thereby minimiz-
ing liabilities, and conserves resources. Through
recycling, the reclaimed solvent becomes a usable
product, no longer a waste. Most industrial  sol-
vents are derived from crude oil, a nonrenewable
resource. The energy  requirements for recycling
are a fraction of those required for producing virgin
    Flexibility  in recycling capabilities allows
reclaimed solvents  to meet manufacturing
specifications as stringent as those for virgin sol-
vent, depending upon the application. Recycling
can be accomplished on-site (at the generators
facility) or off-site at permitted treatment storage
disposal facilities. General factors influencing the
recycling process are:

    • Market value of the virgin solvent,

    • Ease of separation (this can be
     complicated by lack of segregation during
     the waste generation process),

    • Yield,

    • Viscosity,

    • Cost of other disposal options, and

    • Halogen and fuel value.

When recycling methylene  chloride, the typical
waste stream is high in halogen and low in fuel
    Advantages of on-site reclamation  are better
quality control and a reduction in liabilities and
costs associated with waste transportation. How-
ever, on-site reclamation is effective only if a com-
pany has use  for  the reclaimed  solvents.
Additionally, high volumes are necessary to justify
the cost of purchasing, operating, and maintaining
recycling equipment. Off-site recycling facilities
offer the following advantages:

    • Economies of scale of processing,

    • Analytical support for quality assurance
     and control,

    • Outlets for reclaimed chemicals,

    • Fractionatlon capabilities,

    • Technical support, and

    • Ability to blend by-products to obtain the
     most cost-effective method for disposal.

    There are two basic types of commercial sol-
vent recycling. One is custom toll recycling, where
spent solvents are segregated, batch processed
separately  to  meet  specifications,  and then
returned to the original generator.  This type of
processing requires a minimum quantity  of sol-
    The second form involves combining similar
wastes and selling the recycled product. This type
of recycling is available to virtually all  industries,
regardless of the quantity of waste.
    Common to both operations is the need to
properly  segregate wastes. If several  different
waste steams are commingled, the refined solvent

will probably not meet specifications or will require
prohibitively expensive processing, leaving dis-
posal as  the  only  alternative. There are cases
where segregation  Is  not critical; however, In
general, better segregation results in more low cost
processing options.
    If segregation  is  not possible, companies
should determine which solvents are compatible
with methylene chloride recycling.  Romlc Chemi-
cal Corporation's recycling processes tolerate a
variety of cosolvents. Specifically, all water-soluble
solvents (not total toxic organic solvents) with a
fuel value of  10.000  BTU Ib'1 mixed  with
methylene  chloride have processed smoothly.
Even nonwater-soluble solvents are fine—If they
have fuel value, they don't form an azeotrope with
methylene chloride and distill at different tempera-
tures (again, not toxic organics).
    This may appear to be restrictive, but It is not.
There is only one exception—hexane—and even It
can be  processed,  although with  difficulty. The
problem compounds contain halogens.  Notably,
chlorofluorocarbon-113  (CFC-113), which can
render methylene chloride  waste streams  non-
recyclable. CFC-113 and methylene chloride form
an azeotrope for which no published method of
separation exists. This azeotrope (called TMC) has
uses of its own. but they are more limited. Addi-
tionally,  chlorofluorocarbons of many types are
being phased out as known ozone depleters. If
CFC-113 must be used, segregate the stream.


One effective method to minimize waste is to reuse
it as a product In a process or as a solvent In a less
critical application.
    Several paint  and coating manufacturers
report applications that use solvents efficiently.
One successful method is reuse of wash solvents
in an initial rinse, followed by a clean solvent rinse.
An example Is reusing solvents from an ultrapure
degreaslng operation as a first wash in a cascading
application, allowing  several reuse  cycles. In
another method,  waste solvents collected in 55-
gallon drums settle for several days. The decanted
solvent is used to clean noncritical equipment like
spatulas. This process, repeated until no useful
solvent remains, is superior to the first method but
requires more storage space. While both methods
reduce the volume of waste, the waste produced is
dirtier and sludgler.
    If reuse is not possible on-site, companies can
use a waste exchange  service. Contact  the U.S.
Environmental Protection Agency for more infor-
mation about these businesses. Unless your waste
has  significant value and is not  heavily con-
taminated, you will be wasting your time trying to
use an exchange program.
   The most common method of reuse Is to blend
wastes to meet fuel specifications for cement kilns.
Cement companies set specifications for the sup-
plemental fuel they blend with conventional fuels
for ovens  used In cement manufacturing. This
process is extremely effective and operates in a
manner very similar to rotary destructive  in-
cinerators, but it  does not produce a hazardous
   Depending  upon the nature of the waste
stream, solvent recyclers use a variety of process-
ing techniques to  render waste amendable as an
alternative fuel. They Include:

    • Distillation,  to allow for the removal of
      unwanted chemicals such as halogenated

    • Blending, to adjust the BTU value and
      viscosity, and

    • Liquefaction, to suspend solids In solution
      so they behave as liquids.

   Clearly, for methylene chloride waste streams,
distillation  allows  for  recycling.  Blending of
remaining fuel-value solvents yields the alternate
cement kiln fuel. Also, since waste  minimization
techniques result in more sludge, liquefaction will
suspend the solids for future blending. Each of the
processes are Joined by the necessity  to have
quality control measures  that are achieved
through   extensive  analytical testing. When
processing waste, companies  must  have
laboratory support not only to understand what
they are processing but also to know the spectrum
of products the processing will yield.


Wastes that cannot be recycled or reused are sent
for treatment and/or disposal. The most common
options Include landfilling,  deep-well injection.
chemical treatment, biological treatment, and in-
cineration. However, these technologies deplete
natural resources.
   Liability is often the driving force behind a
waste management method, therefore Incineration
is often the  technology of choice. However, with
better management, wastes could be handled by
recycling or reuse  methods.

                                                                      Reducing Risk In Paint Stripping

The underlying forces behind hazardous waste
reduction—legislation and the price of disposal—
will continue to be the main motivators In the
development of waste  management  strategies.
Recent environmental regulations are dictating a
new climate for resource conservation. To remain
viable  in the highly competitive international
market,  Industry must continue to  reexamlne
waste management practices and strive to reduce
costs and liabilities.
    By recycling solvents and employing alternate
fuel production, we are conserving natural resour-
ces and lessening our dependence on foreign oil
Imports, positively affecting the balance of pay-
ments. Romic Chemical Corporation and other
members of the National Association of Chemical
Recyclers have worked to develop effective waste
management strategies to handle  the  recovery
problems of the nineties.  If industry can have a
functional means of handling solvent waste, we
can all move toward a cleaner, more pristine en-

            Questions  & Discussion
       Opening sessions in the Original Equip-
       ment Manufacturing section provided an
       overview of applications for paint strip-
ping In specific manufacturing industries. Follow-
ing a presentation by  Jack Davis of General
Motors' Truck and Bus Division in Flint. Michigan.
participants discussed in more detail particular
Issues related to the cleaning of paint overspray in
spray booths used by the automotive manufactur-
ing Industry. Questions also focused on the
development of new coatings  for automotive
finishes and the possibility of formulating coatings
that are more easily stripped by available means.
John  Grainger,  who presented Information on
reject stripping in the metal finishing Industry.
was asked about the specific composition of cer-
tain semi-aqueous strippers being used in that
   Later sessions Included descriptions of sub-
stitute, non-methylene chloride solvents and non-
solvent technologies available for industrial paint
stripping. Discussion in these sessions addressed
some of the specific details of the technologies and
formulations and  their  relevant applications to
manufacturing industries.
   Christine Whittaker. chairperson for the OEM
sessions, asked about the range of part sizes that
could be  stripped using the cryogenic coating
removal system. Ashok Mathur, who presented
details of the system, discussed Its current ap-
plications as well as the potential for the equip-
ment to be adapted to larger parts.
   For plastic media blasting, some questions
focused on the parameters of the separation sys-
tems used to recover and recycle the blast media.
Specifically,  participants were Interested In learn-
ing what remaining contamination would be found
in the blast media after cyclone separation. Joe
Konopka described the  use of an  adjustable
cyclone to tailor the separating system to the grit
that Is being separated. Also mentioned was the
availability  of mechanical separation systems.
which can often provide a cleaner separation than
a cyclone system. This is particularly important
since dust loadings in the media can reduce the
strip rate.
   Following the presentation on water blasting,
there  was  additional discussion on the  pos-
sibilities of adding participate media to the water
jet. It was noted that there have been applications

where media such as garnet have been added and        The use of sponge blasting for lead paint
that the result is a very aggressive or powerfully     removal was discussed with regard to the potential
abrasive waterjet cutting tool. It was emphasized     for exposure to lead residues through air or water
in discussion of water blasting that the technique     contamination. Participants asked about the costs
is not appropriate for uncured, soft, or tacky     of sponge blasting and the ability to recover spon-
palnts such as those encountered in spray booth     ges for cleaning and re-use in other blasting opera-
cleaning,                                          tlons.

Current Paint Stripping Practices
              Chair: James Gideon
          Division of Physical Sciences and Engineering
        National Institute for Occupational Safety and Health

Paint Stripping  Alternatives for Aircraft
William D. Stevens
Delta Air Lines Inc.
Atlanta Georgia
I     would like to preface my remarks by noting
    that I speak only for the current views of Delta
    Air Lines, not the commercial air Industry In
general. I stress "current" because environmental
Issues and requirements pertaining to them are
changing rapidly.
    Delta  currently operates  a  fleet of ap-
proximately 447 commercial aircraft that range In
size from the Boeing 737 up to the latest addition
to our fleet, the MD-11. We anticipate fleet size to
swell to approximately 500 aircraft by the end of
1991. It Is my department's responsibility to main-
tain the appearance of these aircraft—and uphold
Delta's positive corporate Image.
 Delta's Paint Scheme

 Our paint  scheme covers the  entire  tall and
 fuselage of all our aircraft from approximately the
 wing root over the top. The airplanes' bellies are
 covered with bare polished aluminum. Delta uses
 Crown Metro's epoxy primer and polyurethane top
 coat system, which is electrostatically applied.
 This has been an extremely good system for both
 durability and appearance. Unfortunately, all good
 things come to an end. When our paint starts
 showing the effects of time, we must remove it.
    Until recently, our policy has been to com-
 pletely strip and repaint at every other paint visit
 {with a sanding and coating in between). Our
current philosophy is to totally strip and repaint
at every paint visit, currently at four-to five-year
   Polyurethane paint  is a tough system  to
remove. Currently.  Delta uses a methylene
chloride-based formic acid stripper supplied by
EZE Products. However, we are conscious of the
environmental concerns over using methylene
chloride-based strippers and have been for some
time. We will continue to seek improved methods
and materials to do this job opportunely, economi-
cally, and safely. To this end, we have looked at
and continue to follow the development of these
proposed alternatives:

   • PMB blasting

   • Wheat starch blasting

   • Baking soda blasting

   • Wet ice blasting

   • Dry Ice blasting

   • Water blasting

   We have also been looking into some water-
based acid strippers that have shown increasing
promise as well as the following hybrids:

    • Flash lamp/CO2
    • Pulse laser

    • Paint softener /water blast

    • Paint softener/CO2 blast

    • Paint softener/wheel starch blast

Overview of the Alternatives

PMB Blasting

Delta has followed this method from its Inception
at Republic Air Lines in Atlanta. We have seen this
method progress in military use from manual to
robotic controls that lessen metal surface damage.
However, even with these elaborate controls,
PMB's action  on the soft-clad  surfaces of our
aircraft skin is unacceptable.
    We  continue to follow developments in this
process. In our opinion, PMB is not the solution
because it requires precise controls and mapping
time  and damages the clad  surface. However,
Delta Air Lines does use  PMB  in its  shops for
harder alloys, castings, and steel parts.

Wheat Starch Blasting
Wheat starch is relatively new on the scene, and
we  are following its development closely. At Mc-
Clelland Air Force Base in Sacramento, California,
I witnessed a demonstration using wheat starch
on Delta-supplied panels. The outcome was much
the same as PMB. Some panels that were taken
back and blasted in a controlled  environment
showed more promise;  therefore, we continue to
work with the vendor on this method.

Baking Soda  Blasting
Delta has followed the baking soda process for
several years in tests at our facility. It has been
messy and slow and has caused sandwich cor-
rosion problems.

Wet Ice Blasting

We witnessed a demonstration of this method on
one of our panels recently. After approximately five
minutes of blasting, an area roughly the size of a
50-cent piece was removed. Without some assis-
tance to soften the paint,  this would not be an
effective method to strip large aircraft.

Dry lce/CO2  Blasting
We witnessed a DC-3 being stripped in Oshkosh,
Wisconsin, and were impressed, so we invited the
COa company to Atlanta for an on-site demonstra-
tion. The CO2 process shows excellent abilities to
clean soil from various surfaces and remove soft
paint. During the demonstration, it proved to be
very slow on our poly system. We are considering
a COa system to clean and strip aircraft wheels in
an automated setting and plan to follow this sys-
tem closely.

Water Blasting

This system uses a hydraulic-powered, diamond-
tipped rotating nozzle with 30,000 psl of water. It
removed the paint but left swirls in the metal.
Lufthansa is about to go into production stripping,
using a water system.  Based on the little I have
learned, I think that this method will present some
very serious control problems.
    Most of the hybrid systems are at the research
and development stage: we anxiously await some
positive results.
Delta's Current Paint
Stripping System

Delta continues to use the methylene chloride
stripping system, which has proven fast and effi-
cient. We do not have our head In the sand,
however. Several years ago, we started a trough
system to  contain the stripper and  stripper
residues as they are removed from the aircraft. Our
approach takes the following steps:

    • The aircraft is docked and masked and
      stripper troughs are placed around it.

    • The first stripper is put on the aircraft
      after the troughs are in place. All the
      stripper is removed, along with all of the
      paint on the aircraft's fuselage, after
      approximately four to six hours.
    • Prior to the washdown. the stripper, along
      with the paint residue, is pumped out of
      the troughs for shipment to the chemical
      vendor, who tests It for possible recovery
      and recycling.

    • We are also experimenting with the
      possible recovery of a quantity of
      methylene chloride directly from the
      trough system. No conclusive results have
      been reached yet from these tests.

    Delta is now stripping aircraft in Technical
Operation Center (TOO III. our new stripping and
painting facility. We have attempted to design TOC
III to use today's as well as tomorrow's technology.
The walls are sealed to prevent dust accumula-

                                                                       Reducing Risk In Paint Stripping
tions when and if we decide to go to some type of
blasting media. Also an air supply has been  In-
stalled In the ceiling, as well as  vent exhausts
around the periphery of each bay, to give the best
airflow over the surface of the aircraft during both
the stripping and painting phases of the operation.

   Six stacker cranes are located in the larger bay
to provide access. This bay is capable of handling
the largest commercial aircraft in service today.
The other  two smaller bays have four stacker
cranes in each for access. These platforms are
designed to be entirely self-contained for both
stripping and painting.  We intend to continue the
trough system of stripper collection in the TOC III
facility and hope to fine-tune this system to the
point where we will be collecting and recycling a
large portion of our stripper waste.

Delta Air Lines is looking Into the future today and
planning to be ready. To this point, we are actively
encouraging advancements in chemistry and paint
stripping methods that will help us to perform this
necessary task safely  and in an environmentally
sound manner.

 Media  Blast Dry Paint Stripping:
 The Only Environmentally  Safe Process
 Robert Paul!
 Paul! & Griffin Company
 Vacaville, California
 Charles Owens
 United Airlines (retired)
        Chemical  strippers and the paint  they
        remove are major sources of hazardous
        waste. Conventional chemical paint strip-
 pers have methylene chloride as their major sol-
 vent and those used to remove polyurethane
 coatings on  airplanes  contain  phenol. Both
 methylene chloride and phenol are contributors to
 total toxic organics (TTO) in effluent water and. as
 such, are hazardous wastes.
    Methylene chloride is a carcinogen, and, be-
 cause of its volatility, presents a severe air pollu-
 tion problem. Control of methylene chloride has
 been addressed by the California South Coast Air
 Quality Management District (SCAQMD) in its
 Rule 1401, which requires best available control
 technology for toxics (T-BACT)—the most stringent
 emissions limitation  or control  technique.
 Methylene chloride was listed as a carcinogenic air
 contaminant  by  the California Air Resources
 Board  in June 1990. The U.S. Environmental
 Protection Agency is  expected to take action on
 this chemical  by 1993. Paul! & Griffin Company
 maintains that the best available technology com-
 pletely eliminates chemical solvents.
Dry Paint Stripping with
Media Blast

One of the most innovative alternatives to chemical
stripping is  media  blast dry stripping,  which
eliminates solvent waste and  greatly reduces or
eliminates hazardous waste. Any hazardous waste
generated is from ingredients such as chromium,
cadmium, or lead in the paint system being
removed. We  believe media blast dry stripping to
be the only practicable and environmentally safe
alternative process because:

   • Laser Stripping has not developed Into a
     viable process for removing paint from

   • High pressure water blasting Is ineffective
     against aerospace polyurethane coatings
     without first applying a chemical stripper.

   • Although non-methylene chloride,
     non-phenolic chemical strippers may be
     effective when used in conjunction with
     high pressure water blasting or, in the
     future, developed to the point of working
     by themselves, chemicals will still be
     discharged Into the effluent water.

   • Carbon dioxide dry Ice blasting releases
     carbon dioxide Into the atmosphere.
     which contributes to the Greenhouse
     Effect. This technique also cannot remove
     modern aerospace coatings.

   • Crystalline Ice (water) blasting does not
     remove aerospace coatings.

   • Sodium bicarbonate wet blasting can
     revert to sodium carbonate (soda ash) In
     the presence of water and heat, causing
     corrosion of aircraft structure. It is a
     messy, wet process whose effluent slurry
     requires separation of paint chips and
     occasional pH adjustment before
     discharge. In addition, the pH of blast
     slurry exceeds the manufacturer's limit for
     some aircraft.

                                                                    Reducing Risk In Paint Stripping
   • None of these alternatives Is approved by
     the Federal Aviation Administration (FAA)
     or any transport alrframe manufacturer.
     while media blasting Is approved by
     Airbus, Boeing. Douglas, and the FAA.
Productivity—A Case Study

Having stated that we believe media blast dry
stripping to be the only environmentally safe
process, the obvious remaining question is, how
productive is the process? In October 1990, Lock-
heed Aircraft Services (LAS) Company took the
military transport industry lead  by using the
media blast process to strip a U.S. Air Force C-130.
In this case, plastic media was used. Although
SCAQMD Rule 1401 Initially applies to new, relo-
cated, and modified permit units, Lockheed, as a
front-runner on environmental Issues, took imme-
diate action to comply with the T-BACT provisions.
Other benefits  resulted  from the  choice to use
media blasting, including:

    • Stripping manhours were cut drastically.

    • Aircraft downtime was cut drastically.

    • The U.S. Air Force approved the Job and
     process at first inspection.

    • A thorough post-strip Inspection revealed
     no media Ingress Into the alrframe, as Is
     always the case when proper masking is

    • The South Coast Air Quality Management
     District was delighted with the
     environmental improvement and Issued a
     process permit and Its Clean Air Award to

    • At least 60,000 gallons of water normally
     used and treated as wastewater were not
     used (and thus not treated).

    Further details on this first C-130 stripping
are contained  in Lockheed Aircraft Service
Company's The LAS Word (Volume 38, Number 7,
October 1990). Although Lockheed did not clarify
waste reduction, we estimate that  this operation
will generate, on a production basis, less than nine
drums (55 gallons per drum) of dry waste, which
will not be hazardous unless the  paint being
removed  contains sufficient quantities of
chromium, cadmium, or lead to classify the media
dust as hazardous.
Other Developments

TAT Airlines. Rodez. France, is converting to the
media blasting process, and America West Airlines
has used media blasting exclusively for over two
years at their Phoenix, Arizona, maintenance cen-
ter. In addition, the U.S. Air Force has approved
media blasting on all their aircraft.
   A development study for robotic applications
of the  process was conducted  by Air Canada.
Details are given in Paull & Griffin papers "Robotic
Dry Stripping of Alrframes" and "Robotic Dry Strip-
ping of All-frames: Phase n," SAE Technical Paper
Series  #890926.  Similar robotic application
studies for the U.S. Air Force are contained in Paul!
& Griffin's SAE Technical Paper Series #890936,
"Automated Aircraft Paint Strip Cell." Paull & Grif-
fin Company  has worked  with leading alrframe
manufacturers and the FAA to promote approval
of the dry stripping process for commercial air-
lines. The company's SAE Technical Paper Series
#900971, "Second Generation Airliner Dry Strip-
ping (PMB) Following  Boeing's Specification,"
covers processing requirements for the use of dry
stripping on America West Airlines aircraft when
complying with FAA and Boeing requirements.


Media blasting is a viable process for removing
paint from composites. While there is some
evidence of fiber damage from this technique, the
present method of hand sanding produces more
damage than dry stripping.
   Wright-Patterson  Air  Force Base research
showed that hand sanding caused more damage
to test panels than plastic media blasting (PMB).
The Naval Air Development Center experienced
less damage to the substrate from four plastic
media blasting cycles than from one hand sanding

Process Control and
Employee Training

The key to proper use of media blast dry stripping
is process control and employee training In con-
Junction with the  use of proper blasting equip-
ment. Early testing of  plastic media produced
erroneous results because of media contamination
by sand or dense metal particles. To assure clean
media  when using reclaimed material. Paull &
Griffin developed a  dense particle separator.
Details of this project are covered In our paper.
"New Technology Now—Dense Particle Separator

for  Dry Paint Stripping,"  SAE Technical Paper
Series  #900970. Reams of technical data have
been collected to support  the safety and use of
plastic media. Our technical manual, one of the
most complete repositories of such data, is avail-
able to Interested researchers of the media blast


Paull & Griffin Company is an Industry leader in
the manufacture of blast cleaning equipment. Our
equipment is designed for use with any media:
plastic, carbon dioxide, sodium bicarbonate, or
starch-based.  Thus, our interest is directed
primarily to the equipment system and process

    •  We have rejected the use of dry ice
      because of Its low productivity and
      contribution to the Greenhouse Effect.
    •  We are concerned that sodium
      bicarbonate may revert back to soda ash
      in  the presence of water and heat and the
      effluent slurry mixture discharge may
      require a pH adjustment.
   • While PMB alclad removal is within
     acceptable limits and surface roughness
     does not Increase with repeated blast
     cycles, some commercial airlines do not
     want either clad removal or an increase In
     roughness. Wheat starch appears to be a
     media that will offer vast Improvement In
     alclad removal and surface roughness.
     Our limited testing Indicates that new
     wheat starch media may Initially have a
     low strip rate but that It nears that of
     plastic media when it fractures.

   Paull & Griffin Company believes that media
blast dry stripping Is  the only environmentally
safe,  effective, and  approved (by airframe
manufacturers  and the  FAA) process  for paint
removal.  To provide information on the current
approval status  of dry stripping, we have Included
"A Comparison  of PMB Process Specification on
All-frames" as Attachment A; this is a reprint of
pages  1  through  5, a chart contained  In  our
presentation, "New Generation Dry Stripping—
Major Events During the Last Year and a Com-
parison of USAF, Boeing, Douglas, and Airbus
Process Specifications for PMB."

                         Reducing Risk In Paint Stripping




T. O. 1-1-8
1989 SEPT 1





85891 A / 0386 DD


0.016 IN
0.032 IN




TYPE II (if Type I
cannot strip 0.5
sq ft/min)


1988 NOV 14

2024-T3 CLAD AL
7075-T6 CLAD AL

0.036 IN





1988 OCT 19


0.050 IN
0.050 IN





SIL 51-007
1989 SEPT 6
AIPS 02-100
1990 JAN 30

A-300, A-310
no fiber reinforced
parts coated with
aluminum foil or

1.2 MM(0.047")




40-60 & 60-80

Attachment A Page 1 Copyright 1990 Pauli Griffin Company (4/90) - Reprinted 2/91 for EPA

ATTACHMENT A (continued)


HIGH DENSITY (>1. 991)
OVERALL (>1.575)


0.02% (200 PPM)










40-60 PSI
20-30 PSI

12-24 IN
18-30 IN



0.03% (300PPM)

3/8 & 1/2 IN
(10 & 13 MM)

400-450 LB/HR
700-800 LB/HR

30 W- 5 PSI

14-18 IN
14-48 IN


Ra = 350 n IN
(Ra = 9 n M)

30-60 PSI
25-40 PSI









8 & 16 MM
(5/16 & 5/8 IN)


1.5 BAR(22PSI)

150 MM(6 IN)


(Ra = 276 [i IN)
Ra = 7 n M



   Attachment A Page 2 Copyright 1990 Pauii Griffin Company (4/90) - Reprinted 2/91 for EPA

                                                             Reducing Risk In Paint Stripping
ATTACHMENT A (continued)






12-24 IN





























3.00 X 0.75 IN
(76.2 X 19.1 MM)
0.032 THICK
(0.81 MM)







CLAD 7075
(3.93 X 1 1 .8 IN)
100X300 MM
(0.047 IN)
1.2 MM

  Attachment A Page 3 Copyright 1990 Paul! Griffin Company (4/90) - Reprinted 2/91 for EPA

ATTACHMENT A (continued)






0.0060 IN
(0.152 MM)


(0.006 IN)
0.15 MM



YES, W/CLAD 2024















150 X 150 MM
(6X6 IN)






  Attachment A Page 4 Copyright 1990 Pauli Griffin Company (4/90) - Reprinted 2/91 for EPA

                                                      Reducing Risk In Paint Stripping
ATTACHMENT A (continued)







  Substitute Solvent &
Non-solvent Alternatives
         Chair: James Gideon
     Division of Physical Sciences and Engineering
    National Institute for Occupational Safety and Health

Envirostrip Starch  Blast  Media—A  Safe,
Economical Alternative to  Methylene
Chloride  Strippers
Ruben Lenz
John Oestreich
Ogllvle Mills Ltd.
Montreal, Quebec, Canada
      Envirostrip Is a dry blast media manufac-
      tured from a renewable resource—
      starch—that  is  processed  Into  a
crystallized form. Starch blast media is currently
manufactured from high quality wheat starch in a
patent-pending semi-dry process, without using
chemical additives. Envirostrip blast media does
not pose environmental or occupational hazards.
The product is natural, nonexplosive, and does not
emit an odor during use.
How Envirostrip is Used

Envirostrip is used in commercially available plas-
tic media blast machines. Direct-pressure or suc-
tion type units can be used in small hand cabinets
or large, walk-in facilities. When operators are
removing toxic coatings in walk-in facilities, they
must wear protective suits and have a proper
respiratory air supply.
   A clean, dry air supply for the blast stream and
a metering device for media flow control are both
recommended. Starch blast media has a low
breakdown rate ( 5 percent) and a long life cycle;
it can be used over 20 times at blast pressures up
to 45 pounds per square inch (psl).
Aerospace Applications

Envirostrip efficiently removes many coatings in a
variety of aerospace applications, including:

   • Paint from fiberglass and graphite
     composite materials, including
     dlfficult-to-strip radomes,
   • Paint from clad aluminum, anodlzed clad,
     and anodized aluminum, and

   • Coating from interior aircraft materials
     such as sidewall panels.

   The removal rate depends on the coating-sub-
strate  combination  and  its  condition.
Polyurethane paints can be removed at rates of
0.25 to 1.0 square feet a minute (sq.ft./min.) in
hand cabinets and up to 2.5 sq.ft. /min. in large,
dry-stripping facilities.
   The starch blast media achieves good produc-
tivity without compromising job quality or risking
undue damage to underlying substrates—a major
advantage. It is particularly effective on delicate
materials such as soft metals and composites.
Industrial Applications

Although starch blast media was  primarily
designed to remove coatings from aluminum and
composite materials in aerospace applications.
several other Industrial uses exist, including:

   • Equipment cleaning, particularly where a
     dry method is preferred.

   • Electronic deflashlng, especially where
     electrostatic buildup on components
     cannot be tolerated,

   • Stripping of delicate aluminum and
     magnesium parts, where surface etch
     must be avoided,

   • Engine cleaning where solid abrasives
     must be eliminated from parts before they
     are returned to service.

    • Surface preparation for metallic and
      composite materials, and

    • Metal debarring and mold-cleaning.

Disposal Methods

The waste generated with Envlrostrtp can be dis-
posed of In a  variety of ways.  Legislation  and
methods for disposal depend on the toxiclty of the
coating being removed.
    When Envirostrip Is used for dry blasting, the
media eventually breaks down into a dust that Is
removed from the work area by a cyclone device.
Since the spent dust contains the coating or paint
removed, the nature and toxicity of this coating
will dictate disposal methods.
    The quantity of spent dust generated depends
on the blast pressures and the strip rates. At 25
to 35 psi nozzle pressure, approximately 0.2 to 0.4
pounds of dust are produced per square feet of
surface stripped, while pressures of 35 to 45 psl
produce 0.4 to 0.7 pounds.
    Ogilvie Mills Ltd. recommends disposing toxic-
laden dust as a fuel in cement kilns. This process
provides a safe, economical method of destroying
dry toxic substances. Licensed operators will pick
up the toxic dry waste at a reasonable fee.
    An alternative  disposal method is being
developed for large-scale stripping operations. En-
zyme degradation  of the dust can solubilize the
media in water, enabling separation of the toxic
paint solids through filtration, centrifugation, or
settling. The technique  employs a heat  stable
alpha-amylase enzyme and technology that is well
known to the starch industry. A small concentra-
tion of enzyme ( 0.2 percent) solubilizes the media
within minutes. The paint solids separated out can
be disposed of as a dry toxic  waste,  and the
remaining  filtrate  solution can be digested  in a
waste treatment plant.
   This continuous process is being studied to
determine whether the risk of heavy metals leach-
ing into solution can be eliminated. Since toxic
waste would be reduced by 80 to 85 percent, this
is an economical disposal method.
Economics of Starch
Blast Media

The estimated total cost of stripping polyurethane
or epoxy primer paint systems is $ 1.87 per square
foot, which represents the complete stripping of
aluminum aircraft surfaces to the bare substrate
(see Table 1).

Table 1.—Envirostrip stripping cost breakdown.
 Media consumption
 Manpower ($30/hr)
 Equipment depreciation
 Total stripping cost
 Note: The above estimate is based on typical aviation coatings after three
 years service. Disposal cost is for toxic dry waste.

Envirostrip starch blast media provides a unique
process for coating removal and surface treatment.
For aerospace applications, it efficiently removes
polyurethane and epoxy paints from aluminum
and composite surfaces and can be used  in In-
dustrial applications, such as equipment cleaning,
electronic deflashing, and  surface preparation.
Starch blast media  is used  with  commercially
available plastic media blast machines. The low
breakdown rate and longevity of Envirostrip make
it an economical alternative to chemical strippers.

Crystalline  Ice  Blasting
Sam Visaisouk
IXTAL Blast Technology Corporation
Victoria, British Columbia, Canada

Ice blast technology was developed as a dust-free
coating removal technique  for confined spaces
such as ship interiors and machine rooms. As
research and development progressed, it was evi-
dent that the original concept was only partly
correct. Scientists discovered that the non-
abrasive property of ice particles produced a uni-
quely different effect In blasting and. as a result,
some Interesting Implications and applications
were identified.
Properties of Ice

As a blast medium, ice offers some Important
operational advantages  because of some of its

   •  Ice Is not abrasive. Large Ice cubes are hard
      and can be abrasive, while small ice crystals
      are not,  generally.  Since  Ice  particles
      fracture under a high load, they can limit
      Impact force, thereby preventing damage to
      delicate substrates. Ice can be used to clean
      and decoat systems containing different
      materials, such  as gaskets and plastic
      adjacent to abrasion-resistant materials,
      such as steel. Here, the benefit is in reduced
      preparation time.

   •  Ice undergoes dustless deformation.
      Evident from the outset, this property is still
      Important because It provides a healthy
      environment for  workers and machines.
      Cleanup efforts are also reduced.
     Ice melts to  water. In many decoatlng
     applications In which coating materials
     have known or unknown origins, the debris
     or waste must be contained and handled in
     specified procedures. Spent media—water
     In this case—can be easily separated from
     debris so that waste handling and disposal
     are  not further  burdened.  Waste
     management  involves  conventional
     industrial filtration techniques.

     Ice Is made from water. Industrial quality
     water Is  readily available In most places.
     Ice-making technology is well established
     and  its  cost is more than reasonable, at
     approximately $6 per  ton. To make ice,
     water and electricity are required. The cost
     of both are regulated, which means future
     media costs will be controlled as well.
The Mechanism of Fracture

Since ice Is not abrasive, It does not decoat by the
conventional abrasive processes,  as  does
sandblasting.  While abrasive erosion technology
can be very efficient, it lacks the ability to dis-
criminate the coating material from the substrate.
Figure 1 Illustrates this problem.
   A less dominant way to erode material Is by
fracturing It.  Fracturing takes place when the
impacting particles have sufficient energy to over-
come the fracture threshold of the target.  Under
low Impact energies, conical cracks form. As Im-
pact energies increase, radial and lateral  cracks
appear. The Intersection of these cracks defines a

                                               Initial Blast
               Under Blast
              Over Blast
 Figure 1.—Coating removal by abrasion.

 volume element that is released from the material
 to Indicate erosion, as shown in Figure 2.
    To take advantage of this mode of decoating,
 ice particles of various sizes are  used.  Larger
 particles have sufficient energy to Initiate cracks
 while  smaller  ones can  only extend them. By
 regulating ice particle size distribution, impacting
 energies can also be adjusted to give  optimal
 cracking, which leads to disbonding of large chips
 of coating material, as shown in Figure 3.
    In addition to fracture decoating, a very effi-
 cient mechanism for decoating has been observed
 with ice blast. Paint chips as large as 10 by 10
 centimeters have been dislodged. The theoretical
 and experimental bases of this effect are still being
 System Description
 Ice blasting requires an ice maker, an ice-handling
 module, an air compressor, refrigeration,  and a
 blast nozzle, as illustrated in Figure 4.
Commercial  ice makers are  readily
available.  For  fixed  installations, ice
capacity should  be in the range of 200 to
400 pounds per  hour per nozzle. For large
installations, total ice production could go
up to five tons per hour.

Standard industrial air compressors can be
used. Normal air pressures range from 70
pounds per square inch (psi) for  enamel
decoating to 125 psi for polyurethanes.

A refrigeration unit is required to handle ice
making,  equipment  cooling, and ice

The  ice-handling module integrates all
these units. It  provides proper ice size
distribution  for optimal performance,
precision metering to prevent Ice clogging
and jamming, and low energy transport to
minimize Ice particle attrition.

                                                                       Reducing Risk In Paint Stripping
                                 Ice Particle
                                                                      Sombrero" Structure
                      Radial Crack
            Lateral Crack
Conical Crack
Figure 2.—Crack formation and erosion by fracture.
                                                        For mobile service, all these components—
                                                        along with an air compressor and a diesel
                                                        electric generator are contained in a 40-foot
                                                        trailer.  For normal applications, 50 feet of
                                                        hose is adequate.  Longer  hoses can  be
                                                        accommodated, if required.
Figure 3.—Crack propagation and coating lifting.

    • The blast nozzle is a proprietary design that
      maximizes energy transfer between the air
      blast stream and the ice particles.
Waste  Management

The spent media is water, which can be readily
separated from blast debris. Therefore, there is no
spent media to compound disposal problems. Ice
is made from water, the spent media, which makes
media recycling simple, logical, and economical.
   In typical operations, about 400 pounds of ice
are used per hour. This translates into 40 gallons
of water, of which  some 20  to 40  percent
evaporates during blasting, depending on weather
conditions. A floor drain with a simple filtration
system is all that is required in the facility. Since
ice blast is dust-free,  dust  collection or massive
ventilation systems are not needed.

     Provides refrigeration lor
     ice making and process

     equipment cooling
          Air  Module
      Povides air for process,
      transport and blast
Figure 4.—The OCTAL process system.
     Ice  Maker  Module
Provides crystalline ice

50-4000 Lbs./hr.
                                                Ice  Handling  Module
                                                          Process Computer
                                                          Software Interface
Positive Feed
                Variable ice sizing for
                con foiled impact
                                                              Precision metering
                                                              to prevent clogging
                Low energy to
                minimize attrition
                                                                           Blast Nozzle

Ice blasting Is not abrasive; therefore. It can be
used  to  selectively dlsbond coatings from the
weakest interface, hi multiple coating systems and
under proper operating conditions. It is possible to
lift off the top coat without affecting the primer.
This has been achieved with the DeSoto aircraft
paint  system on clad aluminum. In other decoat-
   ing applications, paint removal down to bare sub-
   strate Is common.
      Ice blast does not damage delicate substrates
   such as glass, fiberglass, plastics, aluminum, and
   rubber gaskets. Because of this, it does not provide
   a white metal finish in the conventional surface
   preparation sense. As ice blast is a relatively new
   process, application and performance standards
   have not been established.

                                                                            Reducing Risk In Paint Stripping
    The following figures provide a general over-
view of the performance and costs of the technol-

• Equipment   Self-contained mobile system with
  description   four nozzles and 2,000 Ibs/hr Ice
• Equipment
  cost         $650,000
• Total
  cost         $25 /hr
• Media cost   None, Included In operating cost
• Utility cost   Minor amount for water
• Strip rate    Polyurethane/epoxy systems: 80-
               100 sq. ft./hr
               Alkyd/enamels: 200 sq. ft./hr
               Epoxles: 50-150 sq. ft./hr
• Labor cost   Four hours for these production rates

 ARMEX/ACCUSTRIP   Bicarbonate Blasting
 Gene McDonald
 Church & Dwlght Company, Inc.
 Princeton, New Jersey

The ARMEX®/ACCUSTRIP™ process Is a low Im-
 pact blasting technology that Is a safe, environ-
 mentally sensible and cost-effective alternative to
 chemical stripping techniques. The process util-
 izes  low pressure blasting equipment—The AC-
 CUSTRIP System,™ with a specially formulated
 abrasive media based on sodium bicarbonate—
 ARMEX® Blast Media. The ARMEX system was
 developed by Church & Dwight, the makers of Arm
 & Hammer  brand baking soda, in conjunction
 with Schmidt Manufacturing Co., the producer of
 the ACCUSTRIP equipment.
   The ARMEX method has found uses in the
 aviation, industrial maintenance, and original
 equipment  manufacturing (OEM) industries. It
 also  has been used effectively on a wide range of
 substrates, from aircraft aluminum and com-
 posites to automotive plastics and from industrial
 tile work to Instrument glass. The baking soda
 blasting system not only removes paint and other
 coatings but also removes grease and oil. The soft
 abrasive nature of ARMEX along with the precise
 control offered by  the ACCUSTRIP equipment
 makes this method applicable  to  virtually any
   Since ARMEX Blast Media is water soluble and
nontoxic, waste disposal is facilitated. Sodium
bicarbonate—more commonly known as baking
soda—Is an excellent source of alkalinity that is
desirable in waste treatment operations. The
paint, grease, and other foreign matter from the
decoating operation are insoluble in the ARMEX
solution and can  be removed by using standard
filter and degreaslng techniques. The resulting
effluent can usually go directly to the waste treat-
ment system. The filtered paint chips and cap-
tured grease are the only potentially hazardous
waste materials, thus greatly reducing the volume
of toxic  waste compared  to chemical stripping
   The ARMEX/ACCUSTRIP system also addres-
ses worker and workplace safety issues. Because
of the benign nature of the baking soda formula-
tion, usually workers need only dust masks and
face shields while working with this system. As
with all blasting systems, ear protectors must be
worn. The net effect is that worker and workplace
safety Is improved  significantly over chemical
stripping techniques while the cost of providing
this Improvement is significantly reduced.
   The simple ACCUSTRIP system is not only low
cost but can be easily adapted to many applica-
tions. Portable systems seem to be the  most
popular currently, but fixed systems also are avail-
able. Although the  ACCUSTRIP is the primary
system using ARMEX, with minor modifications,
the baking soda formulation  can be used with
many systems.
Equipment Description

ACCUSTRIP is a modified wet blast system that
uses compressed air to propel the ARMEX against
the surface to be cleaned. At the nozzle, a small
amount of water is added and atomized. This water
reduces dust generation and, in some cases, helps
cool the surface being blasted (Figs.  1 and 2).
    The key to  the effectiveness of the ARMEX
Blast Media on the wide variety of substrates and
coatings is the precise pressure and flow control
of the ACCUSTRIP system. As developed, the AC-
CUSTRIP system allows the operator to "dial In"
the key parameters appropriate for the job at hand.
Continuing development will further expand the
versatility of this equipment.
    ACCUSTRIP comes in a variety of portable
models and can be Installed as a fixed system. The
system is self-contained and needs only sources of
compressed air and water to make it fully opera-
tional. Because the ARMEX process is a once-
through wet blasting method, expensive air

                                                                  Reducing Risk In Paint Stripping
                                             POT PRESSURE 6AUZ-
                                                                        PRESSURE SMJCC
                              WATCH PIMP
Figure 1.—ACCUSTRIP flow diagram.
                      NOZZLE HOLDER    LONG VENTURI NOZZLE
Figure 2.—ACCUSTRIP nozzle diagram.
handling, recovery, and decontamination auxiliary
equipment are not necessary. The self-contained
ACCUSTRIP system can be purchased for as little
as $13.000.
Process Description

The ARMEX/ACCUSTRIP wet blast process Is an
adaptation of abrasive blasting technology.  The
ARMEX media is propelled by compressed air onto
the surface to be cleaned. Nozzle pressures vary
depending on the substrate type and the thickness
of the coating to be removed, but normally range
between 30 and 60 pounds per square inch. The
media strikes the surface and disintegrates, taking
with It the coating. Water  is injected Into the
media/air stream just prior to the venturi nozzle.
This water atomizes and forms a containment core
around the media, reducing dust generation.
Water volume is normally less than 0.5 gallons per
minute and can be supplied from a garden hose
    The ARMEX, water, and removed coating form
a sludge that is rinsed down with  water. The
ARMEX media is about 10 percent soluble in water
at normal temperatures.  Therefore, about 10
pounds of water are needed for every pound of
ARMEX to completely solubllize It. However,
depending on the coating removed and  the
analysis of the sludge, complete solubillzatlon may
not be necessary for disposal.

   Aside from the ARMEX media itself, the major
difference between the ARMEX/ACCUSTRIP sys-
tem and other blasting techniques is the precise
flow control. Most blast systems rely on nozzle size
and compressor volume to determine the flow.
With the ARMEX/ACCUSTRIP system, flow can be
controlled within 0.25 pounds per minute. Precise
flow control is important for two reasons. First,
only the amount of ARMEX that Is necessary for
coating removal Is used. At equivalent compressed
air volume and nozzle size, the ARMEX/AC-
CUSTRIP system uses 70 percent less media than
other  blast systems. Not only Is this economical
and environmentally sensible, but it also reduces
the risk of substrate damage. Secondly, precise
flow control allows for predictable and repeatable
results. This Is especially important when dealing
with robotics systems and with extremely sensitive
System Performance

The ARMEX/ACCUSTRIP system has found uses
In a wide variety of maintenance and OEM
markets. The system's versatility is directly at-
tributable to the nature of the ARMEX Blast Media.
   Although the equipment is important, the real
key to the ARMEX/ACCUSTRIP process is  the
media—ARMEX.  Based  on sodium bicarbonate
(baking soda). ARMEX Blast Media Is a proprietary
inorganic compound (patent pending) that Is made
to Food and Drug Administration and U.S. phar-
macopeia standards.  Therefore, it is suitable for
use In food plants. The granulation of the ARMEX
media is precisely controlled, which allows the fine
control of medium flow and performance. A series
of ARMEX products (grades) have been developed
to meet the varying  requirements  of industrial
users. Combined with its soft abrasivlty and non-
toxic nature,  the  precise granulation control
makes ARMEX the Ideal media for many different
types of decoatlng operations. The effects of these
and other attributes on the system's performance
are highlighted In the following paragraphs.

Nonflammable,  Nonexploslve,

These features are especially important in  in-
dustrial  cleaning operations like petroleum
refineries and petrochemical plants. The ARMEX
media can be used to decoat  and degrease while
the plants are In operation, thus providing plant
management with significant flexibility and cost
avoidance in maintenance operations. Unlike or-
ganic-based blast media, the dust generated by
ARMEX is not potentially explosive. In addition,
since sodium bicarbonate Is a fire suppressant,
the ARMEX/ACCUSTRIP system provides addi-
tional fire extinguishing capability during main-
tenance operations.

Food Grade Product
Maintenance operations in food processing opera-
tions are sometimes very difficult. The use of haz-
ardous and potentially toxic materials is severely
restricted. Alternatives either require considerably
more maintenance time or present other decon-
tamination problems. The availability of ARMEX,
a  food-grade, water-soluble decoating and
degreaslng system, has  Improved heavy main-
tenance operations in food products plants.

Free Flowing/Precise Granulation

ARMEX Blast Media Is formulated to permit
precise  flow  control through the ACCUSTRIP
equipment. To achieve this precise flow control,
the media must be free flowing under a wide range
of operating conditions. This free-flowing perfor-
mance characteristic along with precise granula-
tions  has permitted the ARMEX/ACCUSTRIP
system  to be used on some extremely Intricate
production line operations in the automotive OEM
industry. In one automotive robotics operation,
the ARMEX/ACCUSTRIP system was demon-
strated to be an effective and economic alternative
to methylene chloride in removing overspray and
in-mold coating from composite panels. Not only
did this application require precise control of the
removal operation, but it also required that the
system start and stop precisely during segments
of the operation. The ARMEX/ACCUSTRIP system
Is easily adapted to meet these stringent require-
ments. A video depicting this application is avail-

Soft Abrasivity

Although this term seems somewhat contradic-
tory, it is an  important attribute of the ARMEX
Blast Media. As long as the ARMEX/ACCUSTRIP
system is operated properly. ARMEX Is sufficiently
abrasive to remove just about any coating from a
wide variety of substrates without damaging the
    hi Industrial maintenance operations, two-
part epoxy coatings over  10 mils thick have been
removed from steel substrates at a rate of nearly
80 sq. ft./hr. More Impressively, fusion-bonded
paints over 20 mils thick have been removed from
piping  systems  at  a rate  of 30 sq.  ft./hr.

                                                                     Reducing Risk In Paint Stripping
Polyurethane top coats and epoxy priming systems
4 to 6 mils thick have been removed from aircraft
aluminum at a rate of 120 sq. ft./hr.
   On steel, aluminum alloys, and other struc-
tural  materials, no change to the substrate is
evident. On softer metals such as clad aluminum,
some  anchor pattern is evident, but far less than
is caused by alternative blasting techniques.
   With plastics, composites, and other sensitive
substrates, the soft abrasivlty of ARMEX has been
very effective. Coating systems removed run the
gamut from acrylics to polyamides to powder coat-
Ings. From graphite epoxy aircraft composites to
polyurethane RIM products in the automotive in-
dustry, economical coating removal rates  have
been  achieved with no appreciable substrate
damage. Care, however, must be taken in system
operation; properly operating parameters must be
established and system operators must be proper-
ly trained. For some operations robotic or semi-
robotic systems are recommended.
   The soft abrasive nature of ARMEX also plays
a part in other aspects of industrial maintenance.
Since ARMEX is  softer than  bearing material
(phosphor bronze, etc.), bearing surfaces on rotat-
ing machinery and equipment do not have to be
masked during maintenance operations when the
ARMEX/ACCUSTRIP system is used. This
provides for significant prep and decontamination
savings in maintenance operations. You  can
literally strip It off without shutting It down.
   In conclusion, ARMEX is sufficiently abrasive
to remove even the most difficult coating, but soft
enough to not damage the most sensitive sub-
strates if the system is operated properly. To bring
the point close to home, ARMEX is similar to the
sodium bicarbonate formula that dental profes-
sionals use to clean your teeth—that's  soft

Waste Management

The ARMEX/ACCUSTRIP  system Is a  once-
through system, I.e., the ARMEX media is not
reusable  as a blasting media. This ensures  that
uncontaminated product is projected against the
surface to be cleaned. This system also reduces
overall cost by eliminating the need for recovery
and reclamation equipment.
   The spent ARMEX media, however, has a use
in waste treatment systems. Most secondary sys-
tems are heavily acid-loaded and require alkalinity
adjustment. Sodium bicarbonate, the main in-
gredient In ARMEX, Is used commercially to  pro-
vide alkalinity and pH control for both aerobic and
anaerobic digester systems. Thus ARMEX, unlike
other stripping technologies, does not generate
any additional hazardous waste as a result of the
stripping process.
   The waste generated by this process is a sludge
containing spent media and the pulverized coating
plus any dirt, oil, or grease that was on the surface.
The typical analysis of this waste indicates that the
removed materials constitute about 1 percent of
the waste, while the remainder is spent media (37
percent) and water (62 percent). A maximum of 8
pounds of waste per minute per operating nozzle
is generated.  Since the rinse water will partially
solubillze this sludge, a containment system must
be In place.
   In the cases where  the pulverized paint or
coating may represent a  toxic waste,  appropriate
measures must be taken to handle It. Since these
materials are Insoluble in water  and ARMEX is
soluble, the potentially  toxic materials  can be
removed by dissolving the spent media waste and
filtering out the insolubles. The toxics can then be
disposed of properly while the liquid effluent can
normally be directed into the sanitary waste treat-
ment system. Analysis of both the soluble  and
Insoluble waste must be done prior to discharge or
disposal to ensure that  all regulations are met.
Actual experience with ARMEX has  shown that
sewering can be carried out in confonnance with
   In some cases,  partial solubillzatlon of the
spent media waste is appropriate. No additional
water beyond the system output of approximately
0.4 gallons per  square foot of area depainted is
added to the spent media.
   The residue is collected and the solids—typi-
cally paint and primer chips, dirt, grease, oil, and
undissolved media—are separated from the sludge
by settling, centrifugatlon, or evaporation/drying.
Actual experience  has shown that sanitary
landfilllng may be appropriate for this solid waste.
However, since coatings and conditions vary wide-
ly, the solid waste must be analyzed and compared
to local and federal regulations.
   With either method, the volume of true waste
as compared  with methylene chloride and other
decoatlng systems is drastically reduced. Unlike
some blast techniques, no pre-wash is necessary;
thus coating removal and waste generation are a
one-step operation.


No description of an alternative new process would
be complete without a full review of the costs.
However, when blast systems are compared with
chemical cleaning systems, it gets a bit like com-

paring apples and onions. The  methods are so
different that you are never sure you can get them
to an equalized base. Further complicating the
analysis are the Inherent differences In coating
systems and substrates. Nevertheless, since cost
evaluations have to be made, we used the following
rationale to determine a standard cost per square
foot of coating removed:

    • For blast systems, we used labor, raw
      materials consumed, capital, energy, and
      waste disposal.

    • For chemical stripping, we used labor, raw
      materials, and waste disposal as the cost

    • Prep costs were  not included because
      these vary so widely, depending on the

    The cost analysis presented in Table 1 is based
on a theoretical aircraft depalntlng operation. It
was prepared to provide the EPA with base data to
compare various stripping methods.

Table 1.—ARMEX/ACCUSTRIP cost analysis.	
                  Aircraft Stripping
         Raw Materials
         Waste Disposal
         Total Cost
$0.77/sq. ft.
 2.40/sq. ft.
 0.02/sq. ft.
 0.03/sq. ft.
 0.27/sq. ft.
 0.02/sq. ft.
$3.51/sq. ft.
                      premium product because of stringent aviation
                      requirements. The use of Maintenance Formula
                      ARMEX would reduce raw material cost to about
                      $1.50/sq. ft. and also should improve the labor
                          Although  comparisons are difficult, Table 2
                      provides the results of an evaluation conducted by
                      ICF In 1989 on the various stripping methods. As
                      you can see the ARMEX method is appreciably less

                      Table 2.—Cost comparison of stripping activities.8
                                                          ICF ESTIMATE
                      TECHNOLOGY	($.LB OF MC)"
                      Methylene Chloride
                      Plastic Media Blasting
                      ARMEX Blasting  	  	
    For other maintenance operations, the costs
will be much lower  because of the cost of raw
materials—the aircraft  grade of ARMEX is a
                       •Costs are compared for the military aircraft submarket of the maintenance
                       paint stripping market.
                       "The sodium bicarbonate estimate was developed in $/sq. ft. and converted
                       to $/lb. of methylene chloride replaced using the methodology presented
                       in the ICF's analysis.

The ARMEX/ACCUSTRIP system is a safe, effec-
tive, and ecologically  sensible system,  a viable
alternative to chemical stripping methods for a
wide variety of maintenance and OEM  applica-
tions. The system has found uses In applications
as varied as winery maintenance and petrochemi-
cal plant maintenance. It has been used to strip
substrates as delicate as aircraft wing composites
and the Statue of Liberty to substrates as substan-
tial as submarine hulls and office buildings. It has
even been used to strip dinosaur bones!

The  Good,  the  Bad, and  the  Ugly—But,
for  a  Few Dollars  More...
Robert M. Carnes
Strlptech International
Mount Pleasant. South Carolina
      Few people in the past  envisioned that
      chemical stripping agents would one day
      be called "caustic" or "toxic" and would
create so much concern with organizations known
as the U.S. Environmental Protection Agency (EPA)
and  the  Occupational Safety and  Health Ad-
ministration (OSHA). Paint residues, along with
chemical  stripping agents, were once dumped in
local ditches, landfills, deserts, or wooded areas.
Once it was discovered that these chemical agents
could be harmful to both personnel and the en-
vironment, efforts were made to eliminate chemi-
cal stripping from the aviation industry.
   Now  that there is  a worldwide  effort to
eliminate chemical stripping, numerous new
processes have been investigated. All too  often,
technicians convince management personnel that
any  form of  alternate  stripping will  severely
damage  aircraft,  while  sales  personnel
demonstrate  equipment to  potential customers
and  claim no damage to aviation substrates. If
chemical stripping had received the in-depth in-
vestigation to which new alternate  methods of
stripping have been subjected, chemicals  would
never have been used on aviation surfaces.
   Everyone wants to resolve the aviation strip-
ping issue one way or another. Management wants
a fast, cheap operation that will satisfy local en-
vironmental officials and OSHA. On the other
hand, the technicians are looking for minor effects
that can be classified as "damage." However, most
of these  technicians know  little about the real
world of aviation and the types of true damage that
aviation skins sustain daily.  Sales personnel want
their equipment to be superior and to be known
for solving all problems.
   They, like management, are driven by  the
profit motive. This report  covers all present
methods of stripping and evaluates the benefits
and drawbacks of each. The report concludes with
a recommendation for a method of stripping that
meets all parameters for both composite and metal
aviation substrates  and eliminates toxic waste
streams and landfill material.
Chemical Stripping

Damage sustained during the chemical stripping
process has been overlooked as an explanation for
the cracking of aviation skins. As modern primers
and paints have become tougher to remove, the
chemicals have become stronger. The phenolic and
formic acid-based  strippers create hydrogen
embrittlement to the skins and make them sus-
ceptible to cracking.
   Any stripper that seeps under skin laps or into
joints and is not completely neutralized with water
can readily cause corrosion and cracking. Usually,
this type of corrosion is not visible until substan-
tial damage has occurred. Acid strippers that seep
into  an electrical wire  bundle or  flight control
cable/rod may set the stage for a possible midair
emergency. Yet. most commercial carrier airlines
do not neutralize with water because of the high
volume of toxic waste produced and the cost of
cleaning the water. Instead, the acid residue is just
scraped off the aircraft and sent for disposal.
About 90 percent of all accidents involving spills
occur during this transportation phase.
   Incineration costs $750-$ 1,200 per 55-gallon
drum. The waste generator is responsible "cradle

to grave" for this "toxic goo." Landfill of methylene
chloride is no longer permitted. Accumulated paint
and primer around rivet heads and In low spots
the chemical stripper did not reach are abraded
with rotary sanding discs,  wire brushes,  steel
wool, or Scotchbrite pads.  This creates skin fric-
tion heating, gouges, and minute ruptures; It also
removes corrosion protection and reduces metal
from skin and  rivet heads. The steel wool hairs
Imbed and create galvanic corrosion. Scotchbrite
pads cause Alclad smearing and crack covering.
All this  action decreases strength, Increases cor-
rosion susceptibility, and creates crack initiation
sites. Stress corrosion cracking, filiform corrosion,
galvanic corrosion, and Intergranular corrosion
can result. Abrasion (wools, Scotchbrite. sanding
pads) also removes Alclad, anodlze, and ion vapor
deposited (IVD) protective metals on fasteners.
    Users may continue to chemically strip In lieu
of a blasting type strip operation out of concern
that the soft Alclad top layer may be peened over
a skin crack and thus mask detection (crack heal-
ing). However, it should be noted that chemically
stripped aircraft are usually "rubbed down" with
abrasive pads such as Scotchbrite to remove any
paint nubs or deposits. This process is very effec-
tive, but it also smears the Alclad layer, dramati-
cally masking  cracks. Steel wools may also  be
used, setting the stage for galvanic corrosion and
smearing and removing Alclad.
    There are strong Indications that OSHA will
reduce the volatile organic compound (VOC) limits
for  these solvents from 500 parts per million to
25-75 ppm. Such an amendment to regulations
could result in  the closure of most strip facilities.
Chemicals also remove paints and primers from
under the edges of rivet heads. It is almost impos-
sible to blow primer and paint back  into these
voids.  Even  with electrostatic paint  guns, the
Faraday caging effect prevents paint from coating
under rivet heads, creating an unprotected void to
trap airborne chemical vapors, minute dust par-
ticles, stripping residues, and moisture. A micro
battery Is also  formed, and galvanic and filiform
corrosion can erode the fasteners and surrounding
    Aircraft skins heat and cool and expand and
contract with altitude and weather changes. Skins
are stretched,  compressed,  and twisted during
take-off, landing, and flight maneuvers. The
aircraft Is designed to tolerate this action. If chemi-
cal, mechanical, and heat damage occurs to skins.
the ability of the aircraft to absorb imposed loads
is dramatically reduced. A crack will follow the
path of least resistance, which is from rivet hole to
rivet hole. In-flight air loads and cabin pressuriza-
tlon can do everything else that is necessary to
Insure the disintegration of aircraft skins. Future
and alternate methods of paint stripping should
not repeat the problems caused by chemical strip-

   •  EPA Issues: EPA requires disposal of
      methylene  chloride stripper and the
      removed paint  and primers that may
      contain eight controlled metals  (arsenic,
      barium, cadmium, chromium, lead,
      mercury,  selenium, sliver). Methylene
      chloride Is  no  longer permitted to be

   •  OSHA Issue*: It is estimated that three out
      of every 1,000 people exposed to methylene
      chloride will develop cancer. Both body and
      breathing protection is required, even
      though few strip  facilities  comply. The
      volatile organic compounds to  which
      workers are exposed and which are released
      to the atmosphere are controlled.
Plastic Media Blasting

This method of paint removal has been used In the
United States for eight years, and to date it has
been a low-technology operation. These systems
are very operator sensitive and require great skill.
Systems that have little exacting control of plastic
media flow rates, particle ejection velocity, and air
pressures are in use, and have developed a reputa-
tion for severely damaging aircraft.
    This lack of control over parameters with vari-
able results has caused users to search for other
methods of paint removal. Aviation-grade blasting
equipment has not existed In America until recent-
ly; however, equipment and a robotic technology
that allow aviation paint stripping to be ac-
complished with complete safety on all substrates
have been developed in Europe.
    Many users of low-technology equipment have
switched to softer  virgin manufactured plastic
media In an attempt to reduce aircraft skin
damage. The cost of this media Is greater and the
break-down rate is frequently high, which further
increases the cost of stripping.
    Aviation-grade plastic media equipment with
exacting controls can use cheaper media made
from  hard scrap  plastic. The  media can be
recycled, cleaned, and regraded to virgin media
standards. This hard plastic breaks  down slowly
and strips  faster; coupled with the  right equip-
ment, It is much gentler on aircraft skins that the
softest of plastic media. Aviation-grade equipment

                                                                      Reducing Risk In Paint Stripping
can remove all particles (no matter what the con-
tamination rate) that have a greater density than
plastic on only one pass through the  cleaning
equipment. The clean, graded plastic media can be
reused many times. All plastic media stripping
problems can be solved by using only aviation
quality equipment.

   • EPA Issues:  EPA requires disposal of the
      dry paint and primers  that can  possibly
      contain eight controlled metals  and are
      entrained in  the Inert plastic media. Some
      localities are now concerned with landfllling
      of the inert plastic media because of the long
      environmental breakdown period of these
      substances. Hangar exit air cleanliness Is
      also a potential problem.

   • OSHA Issues: OSHA requires breathing
      protection from the inert plastic dust and
      toxic  paint  dust, as well  as  personnel
      protection from the 15-70 psi of air pressure
      and ejected plastic particles. Hearing must
      also  be  protected  when operating
Wheat Starch Blasting

This media is a biodegradable virgin (99.99 percent
clean) agricultural product.  Aviation-quality
equipment must be used with wheat starch, just
as with plastic media, for cleaning the media of
dense particles. The cost per  pound ($2.25) Is
much higher, and paint removal rates are much
slower (40 to 60 percent) than that obtained with
Type II plastic media.
    This process leaves an acceptable surface on
most composite and  metal  substrates. Wheat
starch is very susceptible to moisture at the 100
percent humidity level. Once wet, it is no longer
effective for stripping, even if dried. Any moisture
from condensation or escaping air around fittings
will quickly form a large sticky ball of wheat starch
that could plug a media recovery and cleaning

    • EPA Issues: EPA requires disposal of the
      dry paint and primer particles  that can
      possibly contain eight controlled  metals.
      Wheat starch Is rapidly biodegradable. EPA
      also requires hangar exit air cleanliness.

    • OSHA Issues: OSHA  requires breathing
      protection from the inert wheat starch dust
      and toxic paint dust, as  well as personnel
      protection from the  15-60 psl blast
      pressure  and ejected starch particles.
      Hearing must also be protected during the
Sodium Bicarbonate Blasting

Sodium bicarbonate propelled under high air pres-
sure onto painted surfaces does an effective job of
removing paints and primers from thin skinned
metal and composite substrates, and from heavy
wall castings. High-pressure water Is injected into
the dispensing nozzle to control the dust problem
during blasting. The clean, virgin material can be
used only once. This fine powdered media is water
soluble, penetrating every place that water can
penetrate under pressure. When  this water
evaporates, the bicarbonate is left as a residue.
The process requires a minimum of 10 gallons of
water per square foot of surface area to wash an
aircraft after stripping to remove the surface bicar-
bonate deposits; this can prevent proper fresh
paint adhesion.
    After the aircraft is painted and  reaches
elevated temperatures on the parking ramp, the
entrapped bicarbonate may convert  to  caustic
soda ash. This sodium bicarbonate media  is a
hydrophllic  material  and  will absorb  minute
amounts of moisture from the air. Studies  per-
formed at the Brown Boveri Research Center  at
Baden, Switzerland, show that small amounts of
moisture vapor held against aluminum  alloys,
high-strength aluminum, and high-strength steels
can cause a rapid onset of hydrogen embrittlement
and crack growth. It would be virtually Impossible
to mask an airplane to prevent bicarbonate media
intrusion. Also, like chemical stripping,  sodium
bicarbonate can remove paint from under the edge
rivets, increasing risk of electrolytic cell corrosion.
Removal of all particles of paint smaller than the
bicarbonate blast media must be performed with
filtration equipment, and the wet micro-paint
chips must be in accord with EPA rules on poten-
tial hazardous residues.
    Bicarbonate removes paints and  primers in
very small particle sizes. Strontium chrornate,
which is used in modern day  primers, is water
soluble, and water is used for dust control in this
process. Strontium chromate contains the heavy
metal strontium, which can be absorbed by the
body and stored in the bones,  and does not
diminish with time and age; the hexavalent form
of chromate is hazardous to humans. For environ-
mental safety, all wastewater  should be free of
these contaminants, and removing the chemicals
from the water is difficult.

    The sodium bicarbonate is more expensive to
use than plastic media when coupled with avia-
tion-grade equipment.

    • EPA Issues: EPA requires disposal of the
      wet paint and primer particles that possibly
      can contain eight controlled metals. Control
      and  cleaning of the water that  can now
      contain   hexavalent   chrome   and
      water-soluble strontium chromate are also

    • OSHA Issues: Breathing protection from
      the nonharmful sodium bicarbonate and
      the toxic paint dust is required,  as  is
      personnel protection from the high air and
      water blast  pressures  and the  noise.
      Personnel protection from the  possibly
      entrained strontium chromate is  also
Water Blasting
Water blasted at 20.000 to 30,000 psi is presently
used to remove surface coatings. Water filtration
and purification are necessary for this operation.
This  stripping  process requires very expensive
robotic  control, precise angles  of impingement,
and exacting dwell times. Again, paint dust mixed
with  water  results in the strontium chromate
problem as  previously discussed. High-pressure
water intrusion through skin gaps and holes could
possibly create flight safety problems. Some skin
damage problems still exist with thin skins and

    • EPA Issues: EPA requires disposal of the
      wet paint and primer  particles that can
      possibly  contain eight  controlled metals.
      Control and cleaning of large volumes  of
      water that can contain  hexavalent chrome
      and  water-soluble  strontium are  also

    • OSHA Issues: Personnel must be protected
      from 20-30,000 psi water blasting and high
      noise levels. Both hexavalent chrome and
      water-soluble strontium may pose a health
      hazard for personnel.

Carbon Dioxide Ice Pellet

This process is a new concept  where small frozen
pellets of carbon dioxide at about minus 70°C are
propelled against painted surfaces at over 200 psi.
The thermal shock causes the paint and primer to
quickly shrink and break the bond between the
paint and aircraft skins. This carbon dioxide ice
pellet process does not at present work well with
thin layers  of paint /primer on  thin  skin
aluminum. The stripping of composites, especially
woven fiber material and  aramid fibers, has
caused breakage of these fibers and matrix pullout
due  to rapid  shrinking of the primers that are
embedded around the composite filaments.
   A potential problem that has not been properly
investigated is the long-term effects of thermal
shock on the Internal aluminum grain structure.
Other unanswered questions Involve the effect of
thermal  surface shock and great temperature
gradient on aviation skins, I.e., the long-term ef-
fects on fatigue life, acceleration of Intergranular
corrosion,  stress corrosion cracking, crack
propagation, and crack growth.  Also, when carb-
on dioxide gas is mixed with water vapor a very
mild carbonic acid is formed. At present, there is
no data on what, if any, long-term damage maybe
associated with this acid formation.  Further, the
pellets must shatter and return to a gaseous state
immediately upon impact, or skin damage can
occur.  High-particle velocities are achieved with
over 200 psi blasting pressures.
   The  media Is a one-time use material.  The
carbon dioxide equipment and the process is more
expensive to purchase and operate than aviation-
grade plastic media equipment to achieve the same
stripping rates.  At present, carbon dioxide Ice
blasting continues to give variable results with the
same equipment.

   • EPA  Issues: EPA requires disposal of dry
      paint and primer particles that can possibly
      contain eight controlled metals.  Control of
      fine paint and primer dust exiting the strip
      facility is also required.

   • OSHA Issues:  OSHA requires personnel
      protection from 200  psi  ice particles at
      -70"C.   Protection  Is  also required  from
      abnormally high gaseous carbon dioxide
      readings in relationship to oxygen as well as
      from  noise and paint primer dust.
Flash Lamp Stripping

This method uses a high-energy light source to
"vaporize" the coatings.  It is a cheap method, but
is very noisy and leaves a carbon deposit on sub-
strates that must be removed with either methyl
ethyl ketone  (a controlled chemical) or  carbon

                                                                     Reducing Risk In Paint Stripping
dioxide ice pellets.  The area of coverage is small
and some problems have been  experienced on
curved surfaces and substrates of different reflec-
tivity.  The process is also very slow.

   •  EPA Issues:  EPA requires containment of
      possible  volatiles  released  to  the
      atmosphere during paint vaporization, as
      well as disposal of burned ash that might
      contain eight heavy metals.

   •  OSHA Issues: Personnel must be protected
      from volatile exposure, high-intensity light,
      and excessive noise.
Laser Stripping

High-energy focused light can do many things,
from micro surgery to manufacturing metal parts
from blank castings. Lasers have many different
names, such as Argon, COa. YAG, CW, Ruby Crys-
tal, and Eximer. Their use on aviation substrates
for effective paint removal is in the early stages of
development. Effective use of lasers will require
expensive robotic controls that follow aircraft cur-
vatures, maintain correct stand-off distances, and
control speed. Slow paint removal rates and high
equipment costs may be a problem, as may the
difference  in substrate  reflectivity.  There are
numerous potential modes of substrate damage,
such as:

   • Chemical reactions

   • Thermal shock

   • Galvanic cell action

   • Mechanical Input/shock

   • Anodized cracking

   • Imbedded carbon

   • Fiber fraying to composites

   • Delamination

   • BPA Issues:  EPA  requires containment of
      possible  volatiles   released  to   the
      atmosphere during paint vaporization, as
      well as disposal of the burned paint ash that
      may contain eight heavy metals.

   • OSHA Issues: Personnel must be protected
      from volatile exposure, high-intensity light,
      and excessive noise.
Water Ice Blasting

Frozen water (ice), crushed and graded to very
specific sizes, is now being used in an attempt to
removed coatings from aviation substrates.  By
pumping the ice particles down the blasting tube
and then injecting 70 to 140 psi of air pressure at
the nozzle, the ice is propelled onto paint surfaces,
whereby the Impact chips or spalls the paint. To
date,  the process has been exceptionally slow.
Very limited data are available on energy transla-
tion and Almen-strip arc-height analysis.  Again,
strontium chromate. which is soluble in water, can
create water contamination problems and person-
nel hazards.

   •  EPA Issues: EPA requires disposal of wet
      paint and  primer that may contain eight
      controlled  metals. The  disposal of large
      quantities of water possibly contaminated
      with hexavalent chrome and water soluble
      strontium is also required.

   •  OSHA Issues: Personnel must be protected
      from high-pressure ejected water Ice (32°F)
      particles and  excessive  noise.  Both the
      hexavalent chrome and strontium In the
      water residue are possible health problems.
Nonmethyiene Chloride

Methylene chloride has produced numerous per-
sonnel and facility problems for a number of years.
To reduce these hazards and problems, companies
have tried to devise other methods of stripping the
new two-part poly paints. Even though the new
chemical  stripping  methods  do not contain
methylene chloride, they do contain numerous
other chemicals, including methanol, methyl ethyl
ketone, toluol, and toluene. All of these chemicals
are both EPA- and OSHA-board controlled. Also,
the majority of all chemical stripping agents con-
tain substances that are presently restricted or
outlawed by the Southern California Clean Air Act.
More states are now following California's lead in
regulating these chemicals and their emissions.
The volatile fumes normally emitted from these
chemicals assault the nasal passages and the

    • EPA Issues:  EPA prohibits release of the
      chemical emissions to the atmosphere as
      well as the possible eight controlled metals
      in the paint residue. Wash water may also
      contain controlled residues.  Disposal of the

      paint and  primer with other chemical
      residues Is required.

      OSHA Issues: OSHA requires personnel be
      protected from skin contact, breathing of
      volatlles,  and  eye damage.   Kidney
      problems can  possibly be caused  by
      exposure to some of these chemicals, as can
      depletion of body fat.
Dissipate Chemical Embrittling

These chemicals are applied to painted surfaces to
rapidly "age" the paint, resulting in numerous
spider web cracks that loosen the paint and leave
a dried crispy film all over the substrate.  Another
stripping process must then be employed to
remove this layer of embrittled paint.
    The process poses several problems. First, the
chemicals used may  be regulated, as are the
volatlles that are produced. A second method of
paint stripping  or blasting must be employed to
remove the hard,  dry, cracked, and crusty paint
from the substrate of the aircraft, further Increas-
ing costs.

    • EPA Issues: EPA requires disposal of the
      paint and primer that possibly contain eight
      controlled  metals.  The  high volatlles
      emitted during the dissipate embrittling
      process  must be contained.  Possible
      residues  may be added to the paint waste,
      requiring safe disposal, as would possible
      dust released from the dry paint.

    • OSHA Issues: OSHA requires protection of
      personnel from exposure to volatiles  that
      cause eye damage and can be absorbed by
      the body.
...But, for a Few Dollars More

Airplane supervisors and maintainers think noth-
ing of spending large sums of money on test equip-
ment to maintain sophisticated avionics.  Special
care is taken of the mighty jumbo Jets that can cost
between $195 and $205 million each. Only the
best training is provided for the maintenance per-
sonnel, and automated technical data centers are
   But, when  it  comes to stripping  aircraft,
managers procure  the cheapest equipment pos-
sible.  The military normally awards contracts to
the lowest bidder, not the most technically com-
petent. The delicacy of aviation skins, especially
the new composites, is forgotten. All too often, the
small amount of money allocated for a stripping
facility and the associated equipment is offset by
large  sums of money spent each month In the
procurement of the  stripping agent, equipment
modification, and disposal costs.  By expending
more money for the basic facilities and equipment,
it is possible to dramatically lower the daily opera-
tional cost and waste by reducing aircraft damage,
down time of aircraft and equipment, and strip-
ping agent costs.

Automated Plastic Media Blasting
The recommendation to use automated  plastic
media blasting is based on thorough investigation
of every form of paint removal in the United States
and Europe over the last six years.  To be con-
sidered a viable process, the method had to meet
three requirements.  First, it had to strip an
aircraft faster than any presently known method,
whereby aircraft turnaround times are consider-
ably reduced over those now experienced. Second,
the process had to eliminate all EPA and OSHA
concerns.  This Includes the stripping agent and
stripping process, as well as waste streams. Third,
the process had to be economical based on cost to
strip per square foot of surface  area.  The
economics of reliability and  maintainability  of
equipment and the  process are also of utmost
concern and Importance.
   The requirements were met with plastic media
blasting coupled with automated aviation-quality
equipment and Type n medium hardness plastic
media for both thin skin metals and composite
substrates. Aluminum as thin as .012" and com-
posites as thin as .016" have been stripped four
successive times with no measurable damage,
based on  data from Messerschmitt, Bolkow and
Blohm (MBB) of Germany.
   In addition, research  indicates that only
robotics can effectively strip large aircraft (see Figs.
1  and 2).  Two years  of testing completed by
Aerospatiale of France and MBB show that a roto-
jet turbine attached to a robotic manipulator can
strip between 861 and 1,291 square feet per hour
(based on paint thickness).  Plastic media is dis-
pensed at approximately 250-285  pounds per
minute from the rotating RPM controlled wheel and
90 percent of all the plastic  and 99 percent of all
dust and paint particles are captured at the point
of stripping (see Fig. 3). With this stripping rate,
a 747 can be depalnted in approximately 10 clock
hours with three  robots and eight manually

                                                                                 Reducing Risk In Paint Stripping

i 	 .


•. ••


Figure 1.—Robotic manipulation stripping the aircraft, tall section.
                            J  III    ;
Figure 2.—Robotlc manipulation stripping the aircraft, fuselage section.

Figure 3.—Roto-jet turbine.

operated computerized hose and nozzle systems
(not counting prep and deprep time). It is possible
to completely strip a Boeing 747-400  in 48 clock
hours, including all operations.

Proper Use and Equipment
To make the equipment economical to use, it is
necessary to recycle the plastic numerous times—
without entraining any dust or paint particles.
The equipment must also remove all ferrous and
nonferrous particles over  1.5 grams/cc on one
pass through the cleaning machine. This requires
installation of a dense particle separator that can
clean media, regardless of how contaminated, to a
99.98 percent factor verified on site by a $40,000
photospectrometric analysis computer. All media
is graded to a preselected size range to 95 percent
accuracy, a higher degree  than is found in the
original barrels of media ordered directly from the
    Air handling systems in both the media clean-
Ing process and in the building are attached  to
reverse pulse air filters to ensure that the air
exiting the building  is 99.94 percent clean—in
other words, cleaner than the  air entering the
    Since this equipment has the ability  to
separate the paint and the plastic, only the paint
remains as an item of environmental  safety con-
cern. There are two methods of making this paint
nonhazardous.  The first is a new totally
automated system produced by Schllck Roto-Jet
company of Germany that removes the eight heavy
toxic metals found in  paints.  This Is the same
company that manufactures the robot, roto-jet
turbine, and computerized hose and nozzle sys-
tems. The cleanliness of the moist paint residue
(similar to damp sawdust) is verified on-site with
a photospectrometric  analysis computer.  The
eight heavy metals are now a minute fraction of
the remaining residue. The only other Industrial
waste stream coming from the automated equip-
ment is pH normalized "clean" water. The moist
nontoxic paint ball can be made Into decorative
nonconstructlon-type bricks  by mixing  with
Portland cement or go to  normal landfill.
    Another method for detoxifying paint removed
from aircraft has been developed by Perma-Fix, an
American company. In this process, the metals
within paint are first converted to a nonleachable
form. For example, although lead Is harmful to the
body, one thinks nothing of drinking from a 34
percent Bavarian lead crystal goblet. If the goblet
broke,  it could be thrown  into a normal landfill
without creating any environmental concern. The
lead is in a nonleachable and encapsulated form.
    After  Perma-Fix converts the metals into  a
nonleachable form, they encapsulate the  paint.
Several processes can be used, one of which is to
mix the paint with Portland cement and again
make decorative bricks. The material is also excel-

                                                                    Reducing Risk In Paint Stripping
lent for fill underneath roadways, airport runways,
and building sites. EPA-certified labs have tested
this process and found no problems.
   The plastic  media  that has been used
numerous times is still clean and free of all paint
or primer dust or chips.  It is not necessary to
dispose of this clean plastic material in controlled
landfill.  Type n urea formaldehyde plastic media
produces the same BTU of heat as does anthracite
coal when consumed in a mini blast furnace,
where it produces only a very small amount of high
quality black carbon soot that can be captured
electrostatically in exhaust flues and given or sold
to paint manufacturers.  Clean,  broken-down
plastic media is also an excellent soil aggregate to
be used In lawns and flower beds, as  a filler in
cement projects, or as a base for decorative non-
structural bricks. It can be also sold or given to
cement-curing companies to heat the large kilns.
   As can be seen, these technologies are not a
wish,  but a reality.  The equipment exists, has
been tested, and all abilities to perform the stated
functions have  been demonstrated to the aircraft
manufacturers in Europe.
Questions and Answers
Description of Alternative

   m What i*  the product?  Plastic media
      blasting (using Type II urea formaldehyde,
      only) and Schlick Roto-Jet equipment, both
      turbine and  computer roto-Jet controlled
      hose and nozzle.

   • For what applications is it appropriate?
      All  aviation substrates, including the
      thinnest of metal and composite substrates.

   • How  is  it  used?  Plastic  particles
      (approximately 285  pounds/minute) are
      precisely "slung" onto the substrate from an
      RPM-controlled wheel. Dwell time, angle of
      impingement, and stand-off distance are

   • What are its potential hazards? None.


   • How effective is the process in stripping
      different coatings? Plastic media blasting
      using aviation-quality  equipment can
      precisely strip all presently known aviation
      coatings applied to any aviation substrate.
     It cannot strip leading edge rain  erosion
     coatings and nonskld rubberized coatings.

   • How much  risk  does  plastic  media
     blasting  pose  to the  substrate?
     Aerospatiale  and MBB  have tested the
     roto-Jet turbine and computerized hose and
     nozzle (against all other forms of stripping)
     and found no damage to substrates.

   • How much time is required for stripping
     with plastic media blasting (expressed in
     elapsed time and labor-hours)? Roto-Jet
     turbine equals 861-1,291 square feet/hour
     using one labor hour. Computerized hose
     and nozzle equals  60 square  feet/hour
     using one labor hour. Chemical stripping
     equals 20 square feet/hour using one labor

Waste Management

   • IB the material used recyclable?  Type n
     plastic media coupled with aviation-quality
     equipment can be recycled 8 to 10 times.

   • How much waste is generated? What  is
     in the waste? Two streams are generated:
     clean plastic media too small for reuse (3-5
     percent of media used) and the  paint and
     primer chips and dust,  plus the  residue
     dust from the air and media filter systems.
     By-products maybe called "waste," but they
     can be consumed in other ways.

   • How is the waste disposed of?  The clean
     broken-down plastic media can be burned
     in a blast furnace to heat the hangar and
     wash rack water.   The  chimney carbon
     black can be electrostatically captured. The
     paint and primer can be chemically treated
     to  convert the possible eight  heavy
     entrained EPA-controlled  metals to  a
     nonleachable form.  The resulting  mass  is
     encapsulated and  made into decorative
     bricks, used as road bed fill, or placed  in
     normal landfill.

Estimated Cost of Stripping In
Representative Appllcatlon(s)

Cost for stripping is driven by volume of aircraft,
skill in masking techniques, and costs of capital,
facilities, fringe benefits,  waste disposal, labor,
equipment, energy, and so forth. This investigation
found that few, if any, commercial air carriers or
military operations know the  true cost to strip
aircraft.  Any true and total cost between $9-11

per square foot would actually be well within the
total cost now paid for chemical stripping.

    • What in the total cost per representative
      job, and cost per square foot of surface
      area  stripped,  assuming a Boeing
      747-40O hangar and aircraft?

    • Materials cost: Plastic media consumed
      50 cents per square foot for a
      25,000-square-foot 747-400. Cost of
      media Is $1.48-$ 1.60 per pound.

    • Labor cost:  $15 per direct manhour, $35
      per  company manhour.
                        • Waste disposal cost: 18-23 cents per
                          pound of removed paint and primer to
                          detoxify and encapsulate.

                        • Equipment costs (e
                                                                         Reducing Risk In Paint Stripping
                                      APPENDIX 1

     Additional Applications of Automated Dry Media Paint Stripping
Metal Ships/Vessels

• Now in use:   Europe and Asia
• Method:      Semirobotlc manipulator
• Paint and
  nut removal
  method:      Reusable steel wire shot
• Increased
  reduction:    Less manpower, energy, air pollu-
               tion, legal and medical problems,
               OSHA and EPA problems, toxic
               waste. Manipulator washes, scrubs,
               paint strips; removes corrosion,
               prepares for primer and paint.

Paster water wash and brush scrubbing with high-pres-
sure water blasts.

    • Sides washed at 492-1,968 sq.ft. /hour.

    • Bottom washed at 1,453 sq. ft. /hour.

    • Sides scrubbed at 2,090 sq. ft./hour.

    • Bottom scrubbed at 2,096 sq. ft. /hour.

Ship can be stripped of paint and rust.

    • Reusable hard spring steel wire shot Is  thrown
      onto the surface with a controlled speed turbine
      wheel (centrifugal dispensing system).

    • Wire shot ricochets off surface and removes paint,
      primer, and rust. All material Is captured at the
      point of surface Impact and reclrculated.

The paints and primers that are separated from the wire
shot can be chemically treated  to convert the eight
EPA-controlled metals  to a nonleachable form.  This
residue Is thus encapsulated and can now be used for
soil stabilization, road foundation, aviation runway fill,
filler in decorative nonconstructlon brick,  or filler in
blacktop paving. A computer-operated automatic system
also can be purchased to reduce the paint/primer into
a recyclable form.

System Engineering
Adaptable to any dry dock area and suitable for the
largest ocean vessels.

Cargo Containers

• Now in use:   Asia and South America
  Paint and
  rust removal
Semiautomatic manipulator
Steel slag

Containers are loaded onto a con-
veyor and are stripped inside and
outside at the same time with roto-
jet centrifugal wheel turbines. A
visual inspection allows rapid repair
of any previous damage. Automated
system can prime and paint to the
desired color.
Fast, efficient, automatic, reusable stripping media
separates paint and primer from the stripping media; few
people needed.

See ship stripping.

System Engineering
Can be designed and built to suit the size of any opera-

Ground Transportation Vehicles

• Now in use:  Europe, Asia, Middle East, Australia.
              United States, South America,
              Africa, and Canada.
• Method:     Steel shot, steel slag, plastic media,
              garnet stone, wheat starch, coal slag.

Steel trains with rust are best cleaned with an abrasive
material. Totally  automated  systems can be  put
    Stainless steel, thin sheet steel,  fiberglass,  and
aluminum vehicles are best stripped with plastic media.
A good cleaning system to allow  media to be reused
numerous times and effectively remove dust,  paint,
sand, and trash Is essential.
    Automated systems and manual systems can be
used together to most  effectively meet the need  of a
customer and all EPA and OSHA requirements.


Past,  efficient,  safe, reusable media;  removes
paint/primer from the media.

See ship stripping.

System Engineering
System can be designed for specific needs for rail cars,
tractor trailers. Army tanks, cannons,  radar dishes,
corvettes, and subway carriage cars.

Large Pipes

A custom-designed system for stripping, derustlng, non-
destructive Inspection, and coating application for the
Inside and outside of large pipes can be built. Present
applications clean torpedo and missile  tubes of hard
deposits. Other systems can strip large water or chemi-
cal pipes. Even delicate stripping of the air intake tunnel
of the F-16 fighter Is being accomplished.

Now that sand blasting Is being curtailed in many states.
a  fast,  efficient system using reusable  media that
separates  the contaminants from the media Is Impor-
tant. The use of an automatic system Is  safe, fast, and
very efficient with removal rates well above what can be
accomplished by workers.


New systems are presently being developed In Europe to
strip steel bridges with a reusable media that captures
the paint, primer, and media at the point of impact. With
sand blasting rapidly becoming an uneconomical
method to strip large bridges due to the EPA, OSHA, and
"capture" rulings, other methods must be found. The
cost to strip, derust, and  treat bridges has climbed
steadily from 88 to $ 10 per square foot to 824 per square
foot. Whether the bridge has steel girders, cables, open
frame, or tube construction, an economical system can
be developed.
    For waste handling, see ship stripping.

Lead-based House Paint

One of the major challenges facing the housing Industry
and the government today is what to do with the 78
million homes that are covered with numerous layers of
peeling lead-based paint. Automated technology exists
to rapidly strip wood, cinder block, brick, and stucco
homes. This is not a dream but a reality of engineering
and technology.
    The average 2,000-square-foot floor-space house
will average 1,800 to 2,700 square feet of exterior sur-
face. Equipment exists to strip these surfaces at 300 to
1,000 square feet per hour. All necessary Items are
contained In three 40-foot tractor trucks. This Includes
the manipulator stripping equipment, the reclaim sys-
tem, the paint and stripping media separator system, the
environmental air wall system to protect the community,
all plastic canopies, lighting systems, air compressors,
and electrical generators.
    EPA  detoxifying and disposal requirements would
have to be met. Mobile, fully automated equipment exists
that would make the lead paint nonhazardous and yield
the lead as a resalable, recyclable item.

Perspectives on  Surface  Preparation with
CO2  Blasting
Scott Stratford
Alpheus Cleaning Technologies
Rancho Cucamonga California
       Until recently, COz blasting has been used
       primarily as an Industrial cleaning tech-
       nology to remove manufacturing process
residues. Common applications include cleaning
molds, ovens, conveyors, extruders, and presses.
However, there has been Increasing interest in
using COz blasting for paint stripping and surface
preparation because the cleaning agent, small pel-
lets of dry ice, immediately disappears upon im-
pact and returns to  its natural  state  in  the
   The performance of COz blasting has been
overstated in both positive and negative terms for
a variety of reasons.  The net result has been
confusion among end users. Dry ice blasting is not
a panacea that will solve all your surface prepara-
tions needs, but what it does well, it does better
than any other technology available.
   The concept of using dry ice  pellets to clean
surfaces is relatively new. In 1977, Lockheed Cor-
poration filed a patent on a single hose system that
used a supersonic venturl. The system configura-
tion  was later improved to a two-hose system,
which was the basis  for the second Lockheed
   Dry ice blasting was not available as an off-the-
shelf product  until  1986. Two companies in the
United States manufacture COz blasting equip-
ment, one of which is Alpheus. We purchased the
exclusive rights to the  technology from Lockheed.
A third company is located in Europe.
Dry Ice Blasting Process

Although each uses dry ice as the cleaning media,
these companies have distinctly different ideas
about surface cleaning and have designed their
systems to reinforce these concepts. Because of
these engineering differences, it is not possible to
generalize one system's approach with the other
   The core  system is connected to both an air
compressor and a liquid COz storage vessel. Liquid
COz is used to make snow, which is then extruded
into pellets of a predetermined size from 1/4 inch
down to snow.  The pellets are fed through an
airlock out to the nozzle, where  they are ac-
celerated toward the object to be cleaned.
   To evaluate the advantages and limitations of
COz blasting, it  is necessary to understand the
mechanics of surface cleaning with dry Ice pellets.
Visually, COz blasting appears similar to the tradi-
tional process with grit. However, the actual clean-
ing dynamics differ significantly. Grit works
through a chiselling action that not only slashes
or cuts the coating but also the underlying surface.
In contrast, COz blasting can best be described as
an impact-flushing process. As It impacts, the
pellet causes surface and  subsurface fractures In
the coating. The pellet breaks apart and creates a
high-velocity flow of dry Ice particles that mush-
room out from the point of Impact, creating a lifting
and shearing effect. When viewed with high speed

film, the paint seems to be lifted from the Inside
    Intuitively, the Idea of helping the  cleaning
process with a large thermal drop Is both logical
and  appealing.  However, the  belief that  cold
weakens  the  coating system through embrittle-
mcnt and/or the differential contraction between
the coating and substrate Just is not true In most
    With  the  Alpheus  system,  It  Is possible  to
adjust  the temperature of blast air between -100*
and + 100'F. Our testing has shown that, with the
exception of some paraffins, release agents, and
sealants, there Is no benefit from cooling the sur-
face. In fact, with some coatings (such as coal tar
epoxy), supercooling the surface drops the clean-
Ing speed to less than one-fifth of that attainable
at ambient or heated temperatures.
    Another consideration Is the excellent solvent
characteristics of liquid  COa.  It  has  been
hypothesized that—at  the moment of Impact—a
thin layer of liquid COa Instantaneously appears
and then disappears  and that this assists the
cleaning process.
    COa Is a natural  component of our atmos-
phere. Blasting with dry Ice pellets does not create
any additional COa, It  only uses what Is already
there and thus does not contribute to the Green-
house  Effect. The equipment Is reliable, easy to
use, and requires only n half-day of operator train-
Ing. Alpheus has units  In robotic applications
running 22 hours a day, seven days a week.
    COa Is  heavier than air and as such displaces
oxygen. In most workplaces, the amount of COa
coming from the nozzle  Is not a problem; it Is easily
handled  by the facility's ventilation system.  In
closed areas such as  storage  tanks, operators
should use ventilation  and respirators.  Inexpen-
sive COa monitors ran be Installed to automat-
ically  shut down equipment If  the levels  of
concentration exceed  Occupational Safety and
Health Administration standards.


Since there Is no Incremental waste from the pel-
lets, cleanup is confined to the residue removed.
There is no danger of grit entrapment or sedimen-
tation, which reduces or even eliminates the need
to mask or disassemble the area being cleaned.
The process will not affect water usage restrictions
and has been safely used to clean live electrical
subsystems. The pellets will not change the sur-
faces of precision-machined parts. By varying the
blasting parameters, we have successfully cleaned
everything from circuit  boards to I beams.
Dry ice pellets disintegrate upon Impact and there-
fore do not ricochet off the target surface to clean
hidden backsides in complex'structures. Cleaning
performance la generally best when the angle of
impingement Is between 75 to 90 degrees to the
working surface; more glancing blows are Ineffec-
tive for paint stripping. Lastly, COa blasting cleans
down to the original surface geometry. If a new
anchor pattern Is needed, another method mutt
be used.
    Although removal rates can equal traditional
grit blasting in some applications, dry Ice blasting
Is often much slower. Noise levels generated when
operating blasting equipment at high  pressure
(>150 psl) range from 105 to 120 dbA, depending
on the working environment.
    Basic systems start at $100,000.
Good Applications

Surface preparation is rarely limited to the act of
cleaning. As the time and cost of the prc- and
post-cleaning activities Increase for any given ap-
plication, so does the attractiveness of COa blast*
Ing. Two other favorable application conditions
where COa excels are when (1) the surface must
not be  damaged or altered,  or  (2) a company
requires an exceptionally clean, residue-free sur-
   A few examples of good applications are given
In the following paragraphs.

   • Nuclear test oellsi Radioactive epoxy paint
      was removed from high density concrete In
      nuclear  test  cells.  This  two-week job
      resulted In disposal savings of $500,000.

   • Water storage tanks: A company wanted to
      replace a coal tar epoxy coating in a potable
      water storage tank. Power tools  removed
      most of the coating but were unable to clean
      the seams, which was done quickly by COa

   • Pood processing areas! A cracker plant
      wanted  a multi-layered, industrial  alkyd
      coating removed. Grit blasting or solvents
      could be used in the food production areas,
      and the plant's wood floors eliminated use
      of water blasting. COa blasting cleanly
      eliminated the coating.

   • Chemical refineries! Pressure vessels at a
      chemical refinery must have the coating
      over  welds periodically stripped to permit

                                                                      Reducing Rlik In Paint Stripping
      inspection for fatigue cracking. Orlt blasting
      will fold the metal over any cracks, making
      suspect  the results  of a dye pcnetranl
      inspection. COa will clean and strip without
      hiding the cracks and can also remove the
      dye  penetrant  after  the inspection is

   •  Metal plating facilities! Corrosive deposits
      form on equipment, walls,  and ceilings at a
      metal plating plant. Qrlt can  become
      contaminated, creating a disposal problem,
      and water  would activate  the  chemical
      nature  of  the  deposits. COa blasting
      successfully removed deposits and old
      paint, thus providing a residue-free surface
      for repainting.

Steel Structures Painting  Council

Dry ice blasting meets or exceeds the following
SSPC standards.

    •  SP-1 (Solvent cleaning)*

    •  SP-2 (Hand tool cleaning)

    •  SP-3 (Power tool cleaning)

    •  SP-6 (Commercial blast)*

    •  SP-7 (Brush-off blast)

    SP-1 and SP-6 have asterisks, which  I will

    • SP-11 Dry Ice blasting does an excellent Job
      of removing oil, grease, and dirt. Alpheus
      has a unit  In the Space Shuttle  Program
      that high-performance cleans oils and
      partlculates down to the microcontamlnant
      level, even to the  point of removing
      fingerprints. However, all cleaning la simply
      the relocation of dirt from  an unacceptable
      location to another one  that  Is  more
      acceptable. With complex  structures, such
      as printing presses, care must be taken not
      to relocate the dirt to a previously cleaned
      area. Operator skill comes Into play here.

    • 8P-6i COa  blast cleaning meets the SP-6
      standard when there is no heavy corrosion
      and the existing anchor pattern under the
      old  coating Is acceptable. COa blasting
      cannot meet this standard with new steel
      because it will not remove mill scale.
Cleaning Results

Now, how fast does COa blasting clean? Surface
preparation experts would say that the outcome
depends on such things as the coating's thickness.
age, original anchor pattern, and structure com-
plexity—and they would  be right. Nevertheless.
laboratory teat specimens can be a good starting
point for discussion.
   KTA-Tator prepared  multiple  test panels of
eight different paint systems. Each  panel was
grit-blasted to an SP-10 near-white finish with a
nominal anchor pattern of 2 mils. Paint was ap-
plied and cured according to the manufacturer's
specifications. A Taguchl test structure was estab-
lished to optimize the blasting parameters for each
paint system using nine variables, Including pellet
size, velocity, quantity,  and temperature. The
panels were cleaned with COa blast  equipment
until all paint had been removed and the original
SP-10 standard was again achieved. The results
are shown In Table 1.

Table 1.—Cleaning results for test specimens.	
  200 PP/HR      40-80 rr»/HR
• Inorganic zinc

• Vinyl (2 coats)
• Acrylic latex

• Industrial alkyd
  (2 coals)
• Baked enamel
• Coal lar epoxy
  (2 coats)
• Polyamlde epoxy
  (2 coats)
• Epoxy mastic
    Some of the information presented In Table 1
requires further explanation. Let's start with the
inorganic zinc. The removal rate was higher than
we expected. We checked the curing of the sample
and found it was In accordance with  the
manufacturer's guidelines. We are now awaiting
receipt of additional panels to replicate the test.
    The test removal rates for the latex, alkyd, and
coal tar epoxy were all much slower than those In
Alpheus' field experience. For coal tar epoxy and
industrial alkyd. we attribute this to the fact that.
as paint ages, It  loses adhesion and thus COa
pellets remove it more easily. Also, we have had
removal rates In excess of 300 square feet per hour
for latex paint. We plan to explore the reasons for
the slower removal rate In the test.
    The two epoxy systems really are that slow. For
these coating systems, we are testing COa used In
tandem with other technologies.  Maxwell
Laboratories and  Polygon Industries are working
with Alpheus  to explore  COa blasting with their
flashblastlng technology for paint  removal.
Laboratory removal rates of 800 square feet an
hour have been achieved. Alpheus has also worked
with  various  chemical  companies  on pretreat-

merits. These are sprayed on the painted surface,
weakening the adhesive bonds chemically. Then
the paint is removed quickly with COz blasting.

AJpheus has committed significant resources to
furthering the science of COa blasting. At our test
center, a number of projects are being conducted,
    • Quantification of pellet flow upon exiting
     from the nozzle,

    • Effects of supercooled, ambient-heated
     drive air, and

    • Effects of pellet impact energy on coatings
     and substrates.

    Many of the results will be published to help
the industrial community better understand and
use the unique characteristics of COa blast clean-

Water as a Tool:  Alternative  Methods of
Reducing the Environmental and  Human
Health Risks  in  Paint  Stripping
Frank E. Scharwat
WOMA Corporation
Edison, New Jersey

"Water as a tool" la used In many markets and
application*, not only as a paint stripping
medium, but also in cleaning other environmental
and safety conscious applications. Since there are
numerous applications, we have chosen the paint
stripping of aircraft for today's presentation.

Typical Applications In Markets for
Pressurized Water as a Tool
The following industries typically use pressurized
water as a tool:

   • Agriculture
   • Airline
   • Automotive
   • Beverage
   • Building and Concrete
   • Cellulose and Paper
   • Cement
   • Chemical
   • Energy
   • Engineering
   • Food
   • Glass. Porcelain, and Ceramic
   • Iron, Steel, and Metal
   • Military Fields

   • Mining

   • Municipal Services

   • Painting
   • Plastics Manufacturing
   » Public Transport
   • Railroads
   • Shipbuilding
   • Wood

   Pressurized water can be used to reduce the
risk to man and the environment in aircraft paint
stripping applications. Lufthansa Airlines  has
made a substantial investment in a procedure the
Germans call aqua stripping. This approach util-
izes pressurized water up to 500 bar/7.250
pounds per square inch for the safe and environ-
mentally sound removal of paint from aircraft,
Lufthansa estimates that this new  procedure
could save them Initially DM 10 million per year.
as compared to the previous methods utilizing
caustic chemicals.
   Aircraft have to be completely overhauled
every five to eight years. Each "D-check," as It is
called, lasts a good four weeks and usually takes
30,000 manhours to complete. An important part
of such an overhaul involves renewing the paint
job. After thousands of flight hours, even the best
paint is dull, brittle, and cracked. Before, a strong
corrosive agent containing  phenol  methylene
chloride and other substances was applied, which

caused the paint to swell and loosen its hold on
the surface. The paint was then scraped off by
hand. This process was repeated until the surface
was cleaned.
    This procedure has several drawbacks. Phenol
is toxic and highly caustic.  Safety regulations re-
quire workers to wear protective clothing and gas
masks (both of which have to be thrown away after
a single use). These two materials cost Lufthansa
approximately DM 1 million per year. Protective
coverings on the aircraft and surrounding areas
also have to be used and discarded. The residues.
clothing, and coverings have to be disposed of as
toxic waste at great expense. Several tons of waste
material accumulate from stripping the paint off a
single aircraft. The waste material is typically dis-
posed of by incineration, which  pollutes the  en-
    Methylene chloride, highly volatile and known
to cause cancer, is hardly a less critical substance
than phenol. Like all other chlorinated hydrocar-
bons, it  damages the earth's ozone layer. Milder
corrosives are not capable of removing the type of
airplane paint currently in use. Aircraft paint must
meet very high  durability  standards, withstand
scorching heat, and yet be crack-resistant at such
low temperatures as 60°C. Year after year it must
stand up to an intense ultraviolet radiation at
altitudes of 10,000 meters.
    How can airplane paint which is invulnerable
to such  extreme conditions be removed without
inflicting damage on the environment? Chemicals
are not the answer.
    Water as a tool, however, is a perfect solution
as recently demonstrated at the Lufthansa hangar
in  Hamburg. After three years  of testing, con-
ducted  in  conjunction with WOMA Corporation
using pressurized water up to 500 bar77,250 psi,
computer evaluation of the test  data results
revealed certain regularities. If you determine the
type, thickness, and age of the paint used, you can
use a formula  developed to calculate the  ap-
propriate pressure  and temperature.  The  ap-
propriate pump and tools used to apply water at
the appropriate pressure and temperature will
strip off a layer  of paint only one-tenth of a mil-
limeter thick without damaging the aircraft. Some-
times a  chemical swelling agent is  applied to
thicken the paint coat to make it more vulnerable
to the pressurized water spray. Benzyl alcohol is a
perfect swelling agent.  It  is biodegradable  and
completely nonpoisonous. The time required for
the agent to achieve the desired effect is calculated
precisely. If the softening agent is left on for a
longer period, pressurized water spray also will
remove the primer coat.
   In testing this application it had to be proven
that the vibrations and pressures created by the
pressurized jet of water spray did not subject the
airplane's thin aluminum skin to undue stress or
damage.  A series  of tests were carried  out by
independent institutions under the supervision of
Boeing Aircraft  Company. The vibrations and
stresses were measured with lasers and a variety
of other testing equipment, and these values were
compared to those resulting from the mechanical
stress of orbital sanders and polishing machines.
All misgivings were dispelled, and in late 1989,
Boeing gave the go-ahead for the procedure using
pressurized water in paint stripping.
   Boeing is looking for an alternative to harsh
chemical paint stripping in Seattle, Washington.
However, they are placing their hopes on a kind of
shock therapy that calls for spraying aircraft with
a barrage of dry ice crystals. Cold shock causes
the paint to peel off and drop  to the floor with
crystals of dry ice. The crystals of frozen carbon
dioxide (extracted from the air) vaporize complete-
ly, leaving behind only the paint particles on the
floor. That, at least, is how it works in theory. This
technique was  once a favorite  of some of
Lufthansa's engineering  staff. But like so many
other approaches, this one is plagued by nasty
drawbacks. The refrigeration machine and dry ice
blower are voracious consumers of energy. Person-
nel have to wear heavy protective clothing similar
to that used in  sandblasting. Not least of all, the
cleaning area must be equipped with an elaborate
ventilation system to prevent workers from being
knocked unconscious by carbon dioxide vapors.
Furthermore, it has been observed that the heavy
artillery of ice crystals dents the thin aluminum
sheets, leaving the planes' outer skin wavy.
   The same problem occurs when the plane  is
sprayed with granulated plastic. Boeing has ap-
proved  this technique of paint removal  on  its
aircraft, but only one such treatment is allowed
per plane. Stringent safety precautions  must be
taken, since the fine dust cloud of plastic and paint
particles can combine with air to form an explosive
   Paint stripping with laser beams is still at the
laboratory  stage.  In this application,  the laser
would heat the paint to  a point of vaporization.
Many are critical of this approach since problems
such as flltratlon of the resulting gas have not been
thought out.
   Water as a tool in paint stripping has none of
these disadvantages.  At the beginning  of the
decade, water as a tool was successfully used, and
each day we learn a little bit more. This technique
is not only ecologically safer than chemical paint

                                                                       Reducing Risk In Paint Stripping
removal, but it typically costs less and takes less
   A new paint stripping facility is being built by
Lufthansa on the edge of the Hamburg airport
complex. When it begins operation in 1992, the era
of chemical paint removal for Lufthansa will have
drawn to a close. In this new facility, large remote
control units located on platforms and equipped
with six rotating  Jets  will  take on  the task of
stripping paint from the entire aircraft. In a single
work cycle, they will lay bare a swath nearly one
meter wide. It is anticipated that only a few isolated
spots on the airplane will require manual  water
stripping. A processing facility will filter the paint
particles out of the circulating water, reducing the
amount of hazardous material to  be disposed of
and allowing the water to be reused.
   The total investment with this new technology
will have paid for itself in a year's time. But more
important than earnings and the competitive edge
gained by Lufthansa, since aircraft planes from
throughout the world are overhauled in Hamburg,
is the growing sensitivity  to  environmental
problems. Water as a tool addresses problems by
offering an ideal mix of economy and ecology.
    Before you launch any project utilizing pres-
surized water as a tool, be sure to seek a profes-
sional  in the field. I'm sure you will find them
helpful—some companies have more than  30
years of experience. There are variables such as
pressure, flow rate, standoff, speed, and determin-
ing what power source or tools are required, that
have to be considered to accomplish the task. In
many years of experience in this field, I have seen
many people waste a lot of time and money misap-
plying water as a tool. If you take advantage of the
resources available to you, I am confident you will
find pressurized water can solve many problems,
save money, and be a friend to the environment as
well. Paint removal is Just one of many applications
for which you may choose to use water as a tool.

CO2 Pellet  Blasting for  Paint  Stripping and
Coatings  Removal
Wayne N. Schmitz
McDonnell Aircraft Company
St. Louis, Missouri

A major element of every McDonnell Aircraft Com-
pany (McAlr) program is Integrated logistic support
of the fielded weapon system. As more aircraft are
manufactured with composite materials to reduce
weight while maintaining high strength struc-
tures, the requirement to completely remove such
things as paint, primer, and rain erosion coatings
to make bonded repairs becomes critical.
   While composite structures are not subject to
corrosion or fatigue cracking, the remaining metal
portions of the airframe must be inspected peri-
odically  to preclude catastrophic failures from
metal fatigue. Again, surface coatings must be
completely removed to inspect these areas.
   Paint stripping materials that use phenol-
based methylene chloride chemicals are not ac-
ceptable because  composite  materials are
susceptible to damage, and maintenance person-
nel injuries and toxic wastes result from the use
of these hazardous materials. Therefore, McAir
began a search for new paint stripping tech-
nologies  to satisfy integrated logistic support re-
The Search

McAir's search for a new process to strip paint,
primer, and a variety of surface coatings was
conducted under the following constraints:

   • The process must not compromise the
     structural Integrity of the aircraft. This
     requirement is far more stringent than
     merely not damaging the surface of the
     substrate as it includes substructure.
   • Toxic waste and the use of hazardous
     materials must be eliminated.

   • Disposable materials (removed paint, etc.)
     plus any worn-out, contaminated media
     must be reduced by 90 percent.

   • The process must reduce maintenance
     manhours, overall stripping costs, and
     aircraft cycle time by 50 percent.

   The technologies McAlr investigated fell Into
three categories:

   • Dry Media Blasting

     • Carbon dioxide (CO2) pellets
     • Plastic grit
     • Wheat starch
     • Walnut shells (and the like)

   • Liquid Media Blasting

     • Medium pressure (7000 psi) water jet
     • High pressure (32,000 psi) water jet
     • Water Ice slurry
     • Sodium bicarbonate slurry

   • Pulse Light Energy

     • Lasers
     • Xenon flashlamps

   Each of these technologies exhibited one or
more of the following problems:

   • Potential damage to substrates and/or
     substructure (as a secondary effect),

   • Media Intrusion and airframe

                                                                      Reducing Risk In Paint Stripping
    • Damage to polysulfide sealant and rubber
    • Corrosion.

    • Aircraft pre-cleanlng and post-stripping
     cleanup requirements,
    • Hazardous environment for operators,

    • Need for special facilities, toxic waste
     capture system, media-removed coatings
     separation and recycling system, and

    • Spent media and toxic waste disposal
The McAir Choice

A comparative study of these technologies was
conducted to determine which process could effec-
tively strip military specification paint and primer
within the specified constraints. Two additional
categories were added to those identified problems
to arrive at bottom  line effectiveness for each
process:  the life cycle cost benefits for a total
weapon system and the aircraft thru-put rate.
   McAir chose CO2 pellet blasting as the tech-
nology offering the greatest benefits both in terms
of maintenance cost reduction and compliance
with environmental issues. Because the pellets are
made from liquified COz gas (a natural atmos-
pheric element) and sublimate Instantly on con-
tact back to that  gas, they represent an
environmentally safe process for the operator.
   Since there is no media to dispose of, only
paint chips remain. Their volume compared to
toxic  waste generated  by chemical stripping
processes represents a 96 percent reduction. In
addition, CO2 pellet blasting Is generally benign to
most substrates. Since there is no solid media,
intrusion is not a factor, which eliminates the vast
percentage of aircraft masking as well  as post-
stripping cleanup, media disposal costs, and the
requirement for a media separation and recycling
system. Elimination of these tasks reduces main-
tenance manhours by at least 50 percent.
   Another benefit of CO2 pellet blasting is its
ability to remove a broad range of aircraft surface
coatings, sealants, and adhesives. Best of all, there
Is no need to pre-clean the aircraft; the process
Instantly removes such materials as grease and oil
while stripping paint. The economic bottom line is
an overall  stripping cost of $5 a square foot com-
pared to $19-plus a square foot for current chemi-
cal processes.
Concerns about
Pellet Blasting
Every paint stripping technology McAir  inves-
tigated exhibited negative characteristics to a
greater or lesser extent, and none of the processes
has been thoroughly tested  with  respect to all
potential effects on aircraft structures. For all of
its excellent benefits, CO2 pellet blasting still re-
quires further testing for fatigue life degradation,
crack growth potential, and the possibility of in-
ducing micro-cracking in composite materials.
   Some of the effects of CO2 pellet blasting are
visual. At the blast pressures required to effectively
remove paint and primer, soft aluminum skins less
than 0.032 inch thick show evidence of peenlng.
Thermoset composite  materials are easily
damaged unless very close attention is paid to
dwell time and stand-off distance. One other
aspect  of CO2 pellet blasting is a relatively slow
stripping rate  (0.5 square feet per minute) on
alclad-coated aluminum skins and thermoset
composites. Clearly, further  optimization  of the
process is required before CO2 pellet blasting can
be used to remove paint  and  primer from a wide
range of aircraft substrates.

Because  CC-2 pellet blasting offers outstanding
environmental gains, McAir will continue research
on its performance. Preliminary results of combin-
ing CC-2 pellet blasting with other paint stripping
technologies look promising, proving once again
that there are no simple solutions and no one
process is a panacea for all problems.

Pulsed Light  Flashlamp System for Paint
Removal  in Maintenance Stripping
Anthony P. Trippe
Maxwell Laboratories
San Diego. California
         Maxwell Laboratories' paint stripping
         technique uses Intense pulses of light
         to vaporize the paint, a mlcrolayer at a
time. The repetition rate of the  flashlamp, the
intensity level of the light pulsed from the lamp,
the pulse duration (or pulse width), «and the
spectral  content of the lamp's light output all
contribute to the rate of paint removal. Typical
physical parameters of the Flashblast technique
are shown In Table 1.

Table 1.—Typical Flashblast specifications.	
Optical energy density              -1 TO 20 J/cm2
Area covered                    - 20 TO 300 cm2
Pulse repetition rate               -0.1 TO 5 Hz
Pulse width                     - 0.5 TO 2 ms
Power efficiency                 - 30 percent

   A typical Flashblast system Is Illustrated In
Figure 1. One of the major components, the clean-
ing head, contains  the flashlamp, a reflector, a
vacuum  system to  remove vaporized gases and
residue particles, and a flow of cooling water for
the flashlamp. The pulsed power source and power
cable are other major components.
   Some of the Flashblast system's main coatings
removal and treatment applications are:

    • Curing resins and Inks

    • Synthesizing chemicals

    • Purifying silane

    • Annealing semiconductors

   • Preparing surfaces on reinforced plastics

    • Stripping paint from aircraft

    • Maintaining ship surfaces
   • Demilitarizing chemical warfare agents

   • Decontaminating surfaces exposed to
     chemical warfare agents

   • Removing protective oil films from new
     sheet steel

   • Detoxifying synthetic gas

   • Treating Industrial wastes

   Currently, Maxwell Laboratories is developing
commercial equipment that can depalnt military
and commercial aircraft. Figure 2 shows a block
diagram of an industrial Flashblast system that
can remove paint from airplanes.
The Hybrid Technique

A hybrid  approach to flashlamp depalnting Is
being developed by Maxwell Laboratories and a
team of other companies. This technique encom-
passes a system with a robotic crane that carrys a
flashlamp head and COz pellet blast spray head,
along with sensors on its arm. The flashlamp
process removes the paint and the CO2 pellet wash
completes the final surface cleaning.
   A nozzle that accelerates solid COa pellets at
low velocity with a stream of compressed air is
built into the cleaning head behind the flashlamp.
When the pellets hit the surface, a kinetic cleaning
action results from the mass Impact, along with a
scrubbing action from sublimination of the CO2 as
it goes from a solid to a gaseous state. Residual
paint in cracks and  crevices,  along with ash
remaining after Flashback treatment, Is effectively
removed by the CC<2 follow-up wash and flushed

                                                              Reducing Risk In Paint Stripping
                             PULSE POWER
                             19 IN. x (3 TO 6  FT)
                                                     CABLE 10 TO 100 FT
                                                                 LAMPS HEAD
Figure 1.—Typical Flashblast system layout.
                  PULSE POWER MODULE




I 1




^ 1 IfSHT

Figure 2.—Diagram of an Industrial Flashblast system.

off Into the vacuum system. Conventional filters
trap solid particles for safe disposal.
    The sensors provide location information
along with data concerning paint presence and/or
thickness. A logic control unit sensor inputs to
move the robotic arm and select the combination
of flashlamp and COa pellets that will remove the
paint and clean the surface effectively.
Demonstration of Flashblast

The U.S. Air Force conducted an investigation of
the Xenon flashlamp depalnting system, with the
following conclusions:

    • Residue Is minimal,

    • No residue gets into aircraft or avionics,

    • Aircraft do not have to be masked,

    • Depalnted surfaces are ready for new

    • Coatings are removed without damaging

    • The system can be used for metals and
      composites, and it has potential for
      stripping down to the primer.
   Recently. Maxwell Laboratories tested a hybrid
Flashblast-CC>2 pellet blast paint stripping proce-
dure. These trials proved the complementary na-
ture of the two cleaning technologies.
   Additional testing is  underway to determine
optimum cleaning parameters for  a variety  of
paints and  substrates.  Maxwell's next set  of
demonstrations will be conducted with improved
Flashblast equipment  to demonstrate  paint
removal at a rate of 10 square feet per minute.

Maxwell  Laboratories believes that the hybrid
Flashblast-CO2 pellet blast approach is  the best
low-risk alternative for cost effectively removing
paint from aircraft. Several of the system's char-
acteristics that support this assertion Include:

    • No physical contact to treated surface;

    • No chemicals or abrasive materials used;

    • Full control of penetration depth and
     treated layers;

    • Control of spectrum, intensity, and pulse

    • Easily Interfaced into industrial
     environments and automatic systems; and
    • High throughput values for surface

The  Polygon  Paint Removal System
David Van Alstyne
Polygon Industries, Inc.
Lancaster, Pennsylvania

The Polygon Paint Removal System (PPRS) referred
to in  this paper is  a self-contained coating's
removal unit. This Xenon Flashlamp works on the
same  principle as the flash attachment on a
camera but produces light that is several thousand
times  more intense. An electric current is dis-
charged through xenon gases In the lamp. These
gases absorb energy and subsequently release the
energy as photons (light).
   The wavelength of the  emitted light can be
controlled to a certain degree by controlling the gas
composition and pressure  Inside the lamp, the
discharge voltage, and the composition  of the
reflective  material behind the lamp inside of the
head.  Exerting one or more of the controls, the
operator of the PPRS  is able to adjust the light's
wavelength for optimum removal rates of specific
generic paints.
   The light of the xenon flashlamp is pulsed for
a matter of microseconds. In this time, the coating
Is burned without melting. The bl-product of fine
ash and  gases is simultaneously trapped in a
vacuum/filtration system and drawn through an
appendage Into a containment unit. The substrate
undergoes minimal heating. In one study at Mc-
Clellan Air Force Base, Sacramento, CA, February
28. 1987, substrate temperatures increased from
30 to 50°F (17 to 28"C) during paint removal.
   The main components for the PPRS include a
power source (220 VAC), a pulse-forming network
and a controller housed In a console, and a lamp
head or housing. The controller at the console
allows adjustment of power, pulse rates, and on-
off controls.
   The hand-held head is connected to the con-
sole by an umbilical in length of up to 250 feet from
its power supply. The head is also fitted with a
vacuum and to a water source for cooling. Inside
the head and around the xenon lamp Is a reflective
surface that focuses the light flash on the  sub-

With the present and projected demands on the
handling and disposal of hazardous wastes, com-
pounded with the fact that fewer landfills are able
to accommodate such environmental con-
taminants, costs  have escalated. The liabilities
associated with these waste treatments are an
added burden. All of the readily available surface
preparation methods entail the use of chemicals
or blasting. Both of which require labor Intensive
preparatory and cleanup work.
   As a result of these time consuming processes,
workers with specialized skills are taken off of their
designated jobs to accommodate these needs. A
representation of this costly labor Is demonstrated
by large airlines using highly paid engine
mechanics to strip aircraft.






Rgure 1.—Stripping costs par L10-11.
     350  -   	
     200  -
     150  -
                    LABOR (DE-PAINT)
Rgurc 2.—Stripping tabor per L10-11.

                             Reducing Risk In Paint Stripping
Table 1. — A display of cost and time involved in the
PPRS, PMB and methylene chloride methods of
removal for 2 1/3 mils thick polyurethane topcoat and
a Type 2 epoxy primer, on a L10-1 1 series aircraft, with
a removal area of 9,115 sq. ft.
wear $600 $3,000 $9,000
costs $217 $1,200 $1,200

Containment 0 Total housing Total housing
Manhours 76 176 248

Cost of
manhours $3,420 $7,920 $11,160
Amount of waste
produced 100 IDS. 200 Ibs. 285 gals.
dry waste dry waste wet waste
Cost of waste
disposal $180 $360 $3,840
Total cost
containment) $4,717 $12,480 $25,200

Table 2.— The PPRS coating's removal cost/time
analysis of a L1 0-11.
Using the PPRS method to demonstrate the cost and time in-
volved in the coating's removal of an L10-1 1 series aircraft, with
a removal area of 9,1 1 5 sq. ft., 2 1/3 mils thick polyurethane top-
coat, and a 2 1/3 mils thick Type 2 epoxy primer, the following
rates are provided based on two PPRS units, two workers per
Protective wear
(eye, ear, and 4 people @
gloves): $150 each =$600
Labor (prep): 4 people = 1 6 hrs.
4 hrs. per person X $45 per hour
1/2 shift = $720
Labor (strip): 4 people = 48 hrs./60 hrs*
1 2 hrs. per person X $45 per hour
1 1/2 shift = $2.1 60/$2.700*
Time alloted for adjustments of scaffolding and workers.
Containment structure used: no containment needed.
Amortized the investment cost of $250,000 per PPRS unit over
3 years being 1 ,095 days, 1 6 hrs. (two shifts) a day, to arrive at
the hourly rate.
Operational Hourly rate of the PPRS = $14.26
costs: Total hrs. 24
(12 per unit) $342.24
Over half of 1 lamp life + $1 70.00
Electicity $.20 per hr. + $4.80
= $517.04
Removal 2 inches per second at 6 hz. 382.5 sq. ft.
rate: per hr. per unit
produced: 1 00 Ibs. dry waste
Due to the varying weights of the different colored coatings
used on aircraft, we took an average of the costs and weights.
Cost of disposal: = $180.00
Total manhours: - 64 hrs./76 hrs.*
Total cost: $4,177/ $4,717*
Table 3. — Return on Investment over three years, 60
aircraft per year.
Comparing the cost of methylene chloride stripping per L1 0-1 1
series aircraft at $25,200 to the cost of the PPRS stripping per
LI 0-1 1 series aircraft at $4,717 plus/the initial investment of
$500,000 for two PPRS units.
Number of
aircraft MeCL Polygon

1 $25,200 $504,717
5 $126,000 $523,585

10 $252.000 $547.170
15 $378,000 $570,755
20 $504,000 $594,340
•30 $756,000 $641,510
40 $1 ,008,000 $688,680

50 $1,260,000 $735,850
60 $1,512,000 $783,020
+ $7,454.12
in parts
= $790,474.12
* Approximate payback @ 23 planes.
Year 2
80 $2,016,000 $884,814.12
100 $2,520,000 $979,154.12
120 $3,024,000 $1,073,494.12
+ $7,454.12
in parts
= $1,080.948.24

140 $3.528,000 $1,175.288.24
160 $4,032,000 $1,269,628.24

180 $4,536,000 $1,363,968.24
+ $7.454.12
in parts
= $1.371,422.36

Savings: $3,164,577.64

ACKNOWLEDGEMENT: Mark Cohen and Christa
Chiacos helped compile the data presented In this paper.


Automated  Laser Paint  Stripping
Paul Lovoi
International Technical Associates
Santa Clara, California

Automated laser paint stripping has been iden-
tified as a technique for removing coatings from
aircraft surfaces. In December 1989, International
Technical Associates  (InTA)  was awarded Navy
contract No. N00600-90-C-0281 for an automated
laser  paint stripping system (ALPS)  that will
remove paint  from metallic and composite sub-
strates. For the program, which will validate laser
paint stripping, InTA will design, build, test, and
Install a system for fighter-size aircraft at both the
Cherry Point and Norfolk Naval Aviation depots.
    The program Is divided Into four phases:

    •  Phase   I:   validation   testing  and

    •  Phase II: engineering design,

    •  Phase III: system  fabrication  and factory
      acceptance,  and

    •  Phase IV: Installation, testing, training, and
      final acceptance.

    The Phase I test plan is divided Into two parts,
Phases la and Ib.  A laser test lab has been as-
sembled and preliminary testing carried out. The
original test matrix of substrates, coatings, and
testing was extensively revised during the last
eight months to ensure Inclusion of all the needs
of both the weapon system managers and  the
material and structure groups.
    During this process, InTA Identified the need
for a small initial  parametrlzatlon study, along
with physical testing (Phase la) of a small subset
of stripped samples. This subset of tests would
look at such physical parameters as paint surface
conditions after partial stripping,  paint internal
structure after partial  stripping,  composite
damage after  overstrlpplng, and paint  adhesion
from partially stripped surfaces. The la test matrix
consists of the most common coating and sub-
strate combinations and Is centered around physi-
cal tests such as microsectlons, scanning electron
microscope (SEM), and optical microscopy.
   Phase  Ib,  the larger test matrix, covers 15
substrate  coating combinations and a total of
3,779 tests. The Air Force and Army have con-
tributed requirements to this matrix and will fund
service-specific tasks under the Navy contract.
ALPS Technology

The InTA approach to ALPS is best described by
starting with the actual removal of paint, which is
done by a pulsed carbon dioxide laser with high
peak power. Since very high peak powers produce
plasma detonation waves in material, they are not
used. Low peak power or continuous wave lasers
are not used because of significant substrate heat-
ing. This process removes between 150 and 300
micro Inches of coating per pulse, depending on
the type of coating. During the paint removal
process, the duration of the laser's energy and
pulse does not vary, thus simplifying the design.
   The  next step is to decide whether the  laser
should  be  pulsed  at  a given location. A
spectrograph—an Instrument that divides  light
Into different colors—Is used to examine the  color
of the surface before the laser is fired. Colors can
range from near ultraviolet to near infrared, cover-
Ing all visible wavelengths. The spectra of colors to
be removed are  stored In a computer and  com-
pared to the spectra from the coating. If they
match, the laser is pulsed, a small amount of paint
removed, and the color Is reexamlned.  This
process continues until the color no longer
matches the one stored in the computer.
   Rather than working on one area to remove all
the paint, the laser moves on and, after each area
is examined, a pulse is applied or not, as neces-

                                                                       Reducing Risk In Paint Stripping
               r- FRAME OVERLAP
                NEXT FRAME  NEXT FRAME
                             FRAME OVERLAP

                     ADJACENT PATHS OVERLAP


Figure 1.—A series of frames.

sary. This Is called "rasterlng." The raster pattern
covers a 30 by 30 centimeter area, called a "frame,"
that consists of 30 rows by 30 columns (see Fig.
1). Rasterlng allows each area to cool before being
processed again, which is especially important for
coatings  like sealants and on composite  sub-
             strates. Once a frame is clean of any color paint
             whose spectra was stored In the computer, the
             system commands the robot to  move to a new
                The aircraft to be stripped is mapped into a
             series of paths consisting of adjacent frames. To
             ensure that all the paint on the aircraft is removed
             and no lines or bands  of paint remain between
             frames, the frames are overlapped, which removes
             the need for a precision robot.
                To get the laser and end effector to all parts of
             the aircraft, InTA developed a long reach, flexible
             robot system mounted on an air-bearing platform
             that moves from one area to another. This reduces
             the  reach required of the robot and  provides
             flexibility for new aircraft and extension of the
             technology to larger planes. A pictorial of the sys-
             tem components is shown in Figure 2.
                The  material removed from  the aircraft is
             vacuumed up as it is created and sent to a waste
             processor, which separates the waste into partlcu-
             late material and vapors. The participates are
             filtered out. dried, and placed in storage containers
             (Fig. 3). The vapors are oxidized and converted to
      Safety Enelotnre
      Barrier Will
                                        CCTV Cimeri X Y
               1   Beim Delivery
                                      2 Axis Wrilt


3-D Vision

                   T~T1    T1     T
                            Robot Arm
                                                 End EffectorT^
                                                                           Raster Optics
                                                                           3-D Vision
                                                                           WSM Recovery
                                                              To Be
  n	L
| Filiform Drive
                                Tat tine
Later Power Supply

WSM Processor




Platform Drive Control
2nd Terminal
RT Computer
Operator Interface Computer 1 1 Display
Figure 2.—Components of the ALPS system.

                      WASTE MANAGEMENT
                            H20 CO2
                                                     FILTER CAKE
                                        FILTER CAKES
                                        FOR DISPOSAL
Figure 3.—The layout of the waste stream processing system.

carbon dioxide, nitrogen, and water vapor, safe
disposal forms that meet federal, state, and local
Present Program Status

A screening and optimization test matrix has been
prepared to assess laser paint stopping's technical
capability to remove organic coatings from aircraft
exterior surfaces. This matrix, which originally
included test requirements identified by Grum-
man Aerospace Corporation's Engineering Depart-
ment, has been extensively modified. The revised
matrix has been approved by NAVAIR materials
and structures engineers as well as those at the
Cherry Point and Norfolk Naval Aviation depots.
   The Phase la metallic and composite samples
have been stripped and sent  to Grumman
Aerospace Corporation for testing and recoating.
Phase la will be completed by the second quarter
of 1991. The test  panels for Phase Ib have been

  Exposure Control &

  Pollution Prevention
         Chair: James Gideon
     Division of Physical Sciences and Engineering
    National Institute for Occupational Safety and Health

Waste  Minimization  for Army Depot Paint
Stripping Operations
Ronald P. Jackson, Jr.
U.S. Army Corps of Engineers
Toxic and Hazardous Materials Agency
Aberdeen Proving Ground, Maryland

U.S. Army depots perform the overhaul and repair
of tactical equipment. Typical depot maintenance
operations include metal pretreatment (cleaning,
degreaslng, removal of surface coatings) and metal
finishing (electroplating, conversion coating, paint
application) processes. Large amounts of hazard-
ous waste and air pollutants are generated during
these operations. Control,  treatment, and waste
materials  disposal are expensive and often dif-
   Paint removal processes are a major source of
waste generation at Army  maintenance installa-
tions. These operations produce many tons yearly
as exhausted solvents,  spent blast media, waste-
water, sludges, and air pollutants. Consequently,
depot  facilities are  attempting to  prevent the
generation of waste materials at  the source. This
approach reduces the amount that must be track-
ed, treated, and disposed of and can result In
significant cost savings to the installations. Source
reduction also diminishes  the long-term liability
associated with the generation of hazardous
   The U.S. Army Toxic and Hazardous Materials
Agency (USATHAMA) conducts the Pollution
Abatement and Environmental Control Technol-
ogy (PAECT) program  that includes assisting
depots achieve their hazardous waste  minimiza-
tion (HAZMIN) goals. The  program performs re-
search and development leading to adoption of
technology that is required for compliance with
environmental  regulations; will result in sig-
nificant cost/energy savings In comparison with
existing technology; and will allow for minimiza-
tion, recycling, recovery, and reuse of wastes or
excess material in a cost-effective manner. Cur-
rently, USATHAMA is evaluating modifications to
existing depot paint removal processes as well as
commercially available, state-of-the-art tech-
nologies that are more economical and efficient
than existing methods.
   The paint removal method used depends on
the type of tactical equipment being processed and
often varies among depots. This paper discusses
the techniques employed by Army facilities  and
measures being taken to minimize waste from
paint stripping operations.

Abrasive Paint Stripping

A wide variety of abrasive blast media are used
during equipment maintenance  operations at
depot facilities. Types of materials employed In-
clude walnut shells, steel shot, aluminum oxide,
peridot, sand, glass,  and plastic beads. Spent
media are usually disposed of as hazardous waste
because of heavy metal contamination from paint
pigments and surface finishes removed from the
equipment being processed.
   Depots are attempting to minimize waste
generation by using media with longer usable lives.
For example, sand is relatively cheap but fractures
easily. The medium  is  also an  environmental
hygiene concern. Peridot is slightly more expensive
but cost competitive with sand because It is more
durable and recyclable. Steel shot is several times
more expensive than sand; however, it is one of the
most effective media in terms of cost-per-unlt of
surface depalnted. It is extremely durable and can
be reused as many as 50 to 100 times. However,
steel  shot damages sensitive substrates  and
machined  surfaces.  Plastic  beads have been
shown to be more recyclable than most other types
of blast media and do not damage sensitive  sub-
strates such as aluminum.

Plastic Media Blasting

In 1988. USATHAMA conducted  demonstration
testing of plastic  media blasting (PMB) at Let-
terkenny Army Depot (Chambersburg, Pennsyl-
vania) to  assist  depots  in  implementing the
process. Plastic was compared to agricultural
blast  media (walnut shells) and glass beads  to
determine if PMB was a cost-effective alternative.
Results of the test program showed that plastic
media paint removal rates were similar to walnut
shells when performed at optimum operating con-
ditions. Media consumption (waste  generation)
rates  for PMB were about 50 percent lower than
those of agricultural media blasting (AMB). How-
ever, overall depalntlng costs for PMB were 20-to-
30 percent higher than AMB.
    All media tested proved capable of removing
chemical agent resistant coatings (CARC). How-
ever,  neither plastic nor walnut shells removed
deeply pitted corrosion. A combination of 80 per-
cent plastic and 20 percent glass beads success-
fully  removed corrosion but decreased  paint
removal rates about 30 percent.
    Many  depot Installations have implemented
plastic media blasting. Recent reevaluatlons of
paint removal rates indicate that PMB is about 35
percent slower than agricultural media blasting.
The low media consumption rate of PMB is offset
by  the additional time required to  completely
remove surface coatings. Consequently,  some
depots have reported that implementation of PMB
has not significantly reduced overall waste genera-
tion.  Several  depots are investigating  ways to
reclaim the exhausted  plastic media to further
reduce high operational costs and decrease the
amount of disposable waste.

Other Alternative  Blasting Methods

The Joint Technology Exchange Group (JTEG), a
triservlce advisory body, identifies new technology
or processes with the  potential to improve the
efficiency of Department of Defense depot instal-
lations. Several paint removal processes are cur-
rently being evaluated by  JTEG,  Including
high-pressure water, sodium bicarbonate  blast-
ing, carbon dioxide pellets, and plastic media
    Sodium bicarbonate blasting removal rates are
slower than those of the blast media currently
used  at Army depots. The process will generate
sludge that may  require  treatment and/or dis-
posal as hazardous waste. Another potential draw-
back  is that sodium bicarbonate may corrode
some metallic substrates.
   Carbon dioxide blasting, a  relatively clean
process,  is much slower than  current paint
removal methods and may not effectively remove
chemical agent resistant coatings. The possibility
of damage to substrates from thermal shock is also
a major concern. However, the process may be a
waste  reduction technique for cleaning and
degreasing operations requiring the  use  of
chlorinated solvents.
   Neither sodium  bicarbonate nor carbon
dioxide blasting is considered a viable alternative
depalntlng technique for Army depot operations at
the present time. USATHAMA will continue  to
monitor JTEP's test programs with respect to their
applicability for Army use.
Chemical Paint Stripping

Although the removal of paint from tactical equip-
ment is  accomplished with other techniques.
chemical stripping is currently the most cost-ef-
fective method for small, complex parts. Typically,
the equipment to be  stripped Is disassembled
before processing. The smaller parts are loaded
into a basket and placed In a dip tank containing
the stripping  solution. This method generates
large amounts of hazardous waste as spent sol-
vents, wastewater, and paint sludge. Additionally,
paint strippers are 'a source of total toxic organic
(TTO) and volatile organic compound (VOC) emis-
    The U.S. Army Depot Systems Command
(DESCOM) has established a goal of zero genera-
tion for six major waste streams, including chemi-
cal paint removal. Letterkenny Army Depot has
been designated as the Center for Technical Excel-
lence (CTX) for chemical paint stripping. As the
CTX, Letterkenny is  the lead depot for identifying
methods to achieve the DESCOM goal. Some tech-
niques being investigated include replacing strip-
pers containing hazardous materials, increasing
the lives of strippers, and decreasing sludge

Alternate Chemical Paint Strippers
In 1986, the U.S. Environmental Protection Agen-
cy enacted new discharge criteria regulating the
amount of total toxic organic emitted from metals
finishing facilities. The maximum allowable total
toxic organic was established as 2.13 mg/L for
facilities  discharging 10.000 or more gallons of
process wastewater per day. At Army depot Instal-
lations, chemical paint stripping operations con-

                                                                      Reducing Risk In Paint Stripping
tribute approximately 90 percent of the TTO emis-
sions.  A significant contributor is methylene
chloride, the active  component in the Army's
standard chemical stripping formulation.
   Methylene chloride is used in stripping opera-
tions because it can remove almost all types of
paints, Including chemical agent resistant coat-
Ings, relatively quickly without  damaging  the
metal substrates. However, the compound is a
suspected carcinogen and a major contributor of
VOC  emissions. Additionally,  disposal  of
methylene chloride wastes is expensive and often
   The U.S. Army Construction Engineering
Laboratory (USACERL) is completing a study for
USATHAMA  to identify and evaluate the perfor-
mance of commercially available alternate chemi-
cal strippers. The project's objectives  are  to
establish stripping efficiency; alleviate total toxic
organic compliance problems;  and assess  the
health, safety, and environmental hazards of the
identified formulations. The study's results will be
available in August 1991.
   A three-phase approach was used to achieve
this test program's objectives. Approximately 30
formulations were laboratory tested for acceptable
performance during the study's first phase. The
major performance criterion for laboratory screen-
ings was to strip a wide range of surface coatings
within  two hours. The six strippers that met the
stripping performance standard were subjected to
pilot-scale testing at Sacramento Army  Depot
(California). Several other criteria were considered
during the test program's second phase, including
effects  on worker safety, presence of TTO-con-
tributing compounds or other  hazardous
materials, compatibility with metal substrates,
ease of disposal, and cost effectiveness.
   The three most promising strippers from the
second phase were selected  for  demonstration
testing on a depot production line. The strippers
use an oil seal  to retard evaporation, are of a
similar formulation, and require elevated operat-
ing temperatures. The first stripper's evaluation
was completed in 1989. The solution was plagued
by a high evaporation rate and stopped working
after only six months. The second formulation is
presently being  evaluated at Sacramento Army
Depot. The stripper is evaporating at the  rate of
approximately  100 gallons per month,  which
results in monthly materials cost of about $3,000.
The third stripper, currently used in operations at
Red River Army Depot (Texarkana, Texas), also has
an unacceptably high evaporation rate. Both can-
didates do not remove all required surface coatings
and have operational costs at least two-to-three
times greater than methylene  chloride-based
strippers. All three formulations require disposal
as hazardous wastes, which will further Increase
overall operational costs.

Filtration of an Alkaline Paint Stripper

Alkaline paint strippers are also employed during
depot surface removal operations. Over time, an
alkaline stripping solution will lose its strength
because some of the paint residue initially
removed from  parts continues to react with the
active reagents. This residue settles and forms a
layer of sludge at the bottom of the bath. Additional
reagents must be  added periodically to restore
stripping performance.  Eventually,  the  sludge
buildup limits the bath's working depth, and the
addition of reagents becomes so frequent that
replacing the solution is more cost effective. The
spent stripper and sludge must then be disposed
of as hazardous waste. Removing paint residues
from the solution may prolong bath lives, lessen
the number of tank changes, and reduce the num-
ber of waste materials.
   USATHAMA is evaluating the use of a filtration
system to expand the life of a sodium hydroxide-
based stripper at Letterkenny Army Depot. This
study's information will be used to recommend
methods to improve filtration or identify other
ways to extend the lives of chemical paint strip-
pers. The study's final report will be available in
June 1991.
   The  filtration system is being tested on a dip
tank containing approximately 3,000 gallons of
solution. Without filtration,  the tank  must be
replaced every four to six months. Each  tank
change generates about 1,000 gallons of hazard-
ous waste that must be disposed of at a  cost of
$5.50 per gallon. Additionally, refilling the tank
requires approximately $11,000 worth of reagent.
Removing the paint residue  from the  stripping
bath may extend the solution's useful life two to
three times. The Increase in bath life will drastical-
ly reduce waste generation and overall operational
   The filtration system cost approximately
$25,000 and has been operational since January
1991. The unit consists of three filter housings in
series (Fig. 1) currently fitted with 50, 100, and
400 micron bags. The bags are presently emptied
at least twice a week and can be reused several
times. The bag sizes and changing frequency will
be adjusted as the test program progresses. The
sludge is dewatered and collected In a 55-gallon

                       i ict an <: AUD. r
                       UQUIO SAMPLE
                            LIQUID LEVEL
                           TANK 25H
                                         V18         ^  V19
                                        ^XHXHXHXJ— CITY WATER
                                                                       HIAOW PRESSURE
                                                                          SWITCH FOR
                                                                        MOTOR CUT-OFF
                                               PRESSURE GAUGE
                                               YWTH CHEMICAL SEAL
                  AIR CONNECT
--   J
                                                                             3/4" SAMPLE
Figure 1.—Process sketch for the alkaline paint stripping solution partlculate filtration system.
drum as hazardous waste. A progressive cavity
pump Is used to circulate the stripper bath's con-
tents at 50 gallons per minute.
    During the test program's preliminary phase,
the tank was sampled three times over a 44-day
period and factors affecting  its life span were
studied. Solids settling, specific gravity, alkalinity,
and particle size analysis were conducted on the
solution to determine the stripper's and sludge's
characteristics (see Tables  1 and 2). Based on the
data obtained, tank dimensions, bath life, and
                       known depot production rate, It Is estimated that
                       approximately 0.5-1.0 cubic feet of sludge are
                       generated dally.

                       Other Alternative Methods
                       Other alternative paint removal processes have
                       been identified, including molten salt baths, high-
                       temperature air bake ovens, heated fluidized beds,
                       and laser energy. Fluidized bed and laser technol-
                       ogy are described in the following section.

                                                                      Reducing Risk In Paint Stripping
 Table 1.—Summary of analytical results for alkaline
 paint stripping solution at Letterkenny Army Depot.
                            SAMPLE DATE
Total residue (mg/L)
Filterable residue (mg/L)
Nonfilterable residue (mg/L)
Specific gravity liquid
Specific gravity sludge
Alkalinity (mg/L as CaCO3)
End point pH 8.3
End point pH 4.5
341 ,000
 Source: ES&E, 1990.
 Note: NA = Not Analyzed.
 Table 2.—Summary of particle size analysis results
 for alkaline paint stripping solution at Letterkenny Army
 Depot (results reported In microns).
Population data
Volume data












Source: ESE, 1990.
Fluidized Bed Paint Stripper
and Degreaser
The feasibility of using a heated bed of fluidized
aluminum oxide to remove paint and grease from
tactical equipment Is being demonstrated by
USATHAMA at Red River and Letterkenny Army
depots. The systems can remove all types of paints
normally encountered, Including chemical agent
resistant coatings. The process Is an alternative to
chemical dip tanks for parts that can tolerate
temperatures of 750 to 800°F. The ftuidlzed bed
can  significantly decrease hazardous  waste
generation and provides a safer work environment.
   Fluidized aluminum oxide has  heat transfer
characteristics approaching those of a liquid. The
fluidized bed paint stripper (FBPS)  uses heat
transfer between  the  aluminum oxide and the
parts undergoing processing to remove surface
coatings and grease. The amount of air required
for fluidlzation is not sufficient to support combus-
tion in the bed. Consequently, organic con-
stituents of the paint are pyrollzed to carbon and
carbon monoxide while  grease and  oils are
vaporized. The organic material Is combusted in
an afterburner  at 1,400'F. The afterburner ex-
haust is passed through a Venturl scrubber during
operations at Red River to remove any potential
zinc, cadmium, or lead emissions before discharge
to the atmosphere. Figure 2 presents a diagram of
a typical FBPS unit. Any organic grit remaining on
the parts after processing in the bed is removed by
low-energy shot blasting.

                                                        BED ENCLOSURE
                                                                          EXHAUST •*
                                                     COOLING BED HEATED BED
                             VENTURI SCRUBBER
 ••0 orr QMCS

Figure 2.—Components of the fluldlzed bed paint stripper.

   The effects of high operational temperature on
various types of metallic substrates will be deter-
mined during the test programs. Selected parts
from the other trlservices will also be processed.
Data on waste generation, operational parameters,
and production costs will be gathered. Reports on
the FBPS demonstrations  will be available  in
August 1991.

Laser Depainting

Several studies Indicate that paint can be removed
by targeting laser energy directly onto the coating
surface.  Chemical agent resistant coatings, al-
though resistant to most paint-removal systems,
would be susceptible to laser degradation. How-
ever, the use of lasers will Involve high capital costs
because of the sophisticated equipment required.
JTEG is currently evaluating the process.
The Army depots are making progress  toward
meeting DESCOM's goal of zero hazardous waste

generation for six major waste streams, Including    Ing insufficient funding to implement proven tech-
chemlcal paint removal.  The results  of    nology, manpower shortages, and lack of technical
USATHAMA's and JTEG's efforts will assist the    Information transfer among Army and other
installations. However, obstacles remain, Includ-    Department of Defense facilities.

The  Biodegradation  of Paint  Waste
Gail Bowers-Irons
Robert Pryor
Craig Miller
Trung Chau
Technical Research Associates, Inc.
Salt Lake City, Utah
        Ircraft, combat vehicles, logistic equip-
        ment, and ships require constant repair
         id maintenance. Typical aircraft waste
generation numbers are 1.5 tons of material per
C5 or C141 (cargo planes), 0.5 tons of material per
F4 Jet, and 0.4 tons of material per 5,000 square
feet of  commercial plane. Presently,  current
aircraft  chemical stripping requires  365 man-
hours, in addition  to  preparation and  cleanup
time. The chemicals are not reusable, and there is
often a  20,000 gallon  contaminated MEK/paint
water clean-up problem.
    Costs for the current process have been es-
timated at  $10-15/gallon per  100-200 gal-
lon/strip job. Bead blasting requires 36 manhours
combined with additional preparation and cleanup
time. Both of these methods require  a dry strip
method to remove  the  residual  material,
predominately primer. Dry stripping requires 185
manhours per procedure. In the process of dry
stripping, metal is lost. Incineration costs of dry
strip material range from $700 to $1,000 per 55-
gallon drum.
    Enzymatic degradation could replace these
processes.  Technical Research Associates,  Inc.
(TRA), under a Small Business Innovative Re-
search Phase II grant, is developing an enzymatic
paint waste blodegradatlon system. The support-
 ing organization is the Materials  Laboratory,
Wright Research and Development Center,
Aeronautical Systems Division (AFSC), Wright-
 Patterson Air Force Base, Ohio, under contract
 F33615-90-C-5910. The technical monitor is Cap-
 tain Gary D. Meuer.
    TRA is studying mixed Type II bead/Type V
 bead/paint/primer wastes.  The paint/primer
 waste samples were obtained from Tom Byers and
Owen Mitchell, Hill Air Force Base (HAFB), Utah.
The Type II beads are U.S. Technology Thermoset
Urea Formaldehydes. The Type V beads (Dupont
L) are Thermoplastic Acrylics:  stearamidopropyl-
dlmethyl-Beta-hydro-xyethylammonium  nitrate.
The bead/paint  wastes  contain Mil Spec
polyurethane paint and chromate/ strontium
primer.  The results of a representative paint
material data safety sheet (MSDS) are shown in
Table 1. Table 2 shows the results of a repre-
sentative EDAX analysis.

Table 1.—Representative paint MSDS.	
                               WEIGHT PERCENT
 Titanium dioxide
 Amorphous silica
 Carbon black
 Methyl ethyl ketone
 Methyl isobutyl ketone
 Butyl acetate
 Methyl N-amyl ketone
 Methyl ethyl ketone
 Aliphatic polyisocyanate
 Table 2.—Representative EDAX analysis.

 Table 3.—Type II, Type V, and mixed bead/paint waste
 materials solubilization.
Cloudy solution
Light yellow tint
Yellow tint
Yellow tint
Table 4.—Mixed bead/paint UV-Vis spectrophotome-
try analysis.
343 nm
372 nm
370 nm
371 nm
371 nm
371 nm
0.258 A
1.472 A
2.757 A
2.751 A
2.656 A
2.661 A
    The Type II. Type V, and mixed bead/paint
waste materials were placed In 1 molar acid and
base solutions to test solubilization. The solubility
results are shown in Table 3. Table 4 shows results
of mixed beads/paint UV-Vis spectrophotometry
    Blodegradatlon experiments now In process
use a patented and American Type Culture Collec-
tion-registered (ATCC 53922) TRA culture (HAFB-
1). as well as two new Indigenous cultures (HAFB-2
and HAFB-3). TRA can blodegrade a 10 percent
loading in less than 30 hours for a cost of less than
$28 per 55-gallon drum. TRA expects to field test
a scaled,  semlcontinuous system  at HAFB  by
spring 1992.
    Figures 1 and 2 show FTIR scans of Type II and
Type V beads, respectively, vs. mixed Type II/Type
V bead/paint waste. Figure 3 Is an FTIR of non-
proteased blodegraded bead /paint waste vs. un-
treated  bead/paint  waste. All spectra were
converted  to  absorbance  units for the overlay.
These spectra can only be Interpreted qualitative-
ly, based on the wavenumber of location and the
presence or nonpresence of activities at that loca-
tion.  Figures 4 and  5 show  UV-Vis  scans of
blosolubillzed beads /paint waste liquor.
  oooo  jeso 33ao 3070 27«o  2*90 21*0 iaso 1920  1210  soo
                  wovenumber (cm—1)
   File:  PLOTS
                                                    Figure 1.—Fourier Transform Infrared Spectrophotometry
                                                    (FTIR) scans of Type II beads/paint waste. Non-
                                                    biodegradable Type II beads are predominant In these
                                                    mixed Hill Air Force Base bead/paint wastes.
  4000 38so  3300  3070 nso 200 21*0  iaao  1920 1210 soo
                   wavenumber (cm— 1)
    File: PLOT7

Figure 2.—FTIR scans of Type V bead/paint waste.
                                                      4OOO 369O 3.3BO 3O7O  276O 24SO 214O 1830  192O  1210  SOO
                                                                       woveoumDer (cm— I)
                                                       File  PLOT!

                                                    Figure 3.—FTIR scan  of nonproteased  blodegraded
                                                    Type Il/Type V bead/paint waste vs. untreated bead/paint

Vapor Recovery and Recycling of
Methylene  Chloride from  Paint
Stripping  Applications
Paul E. Scheihing
Office of Industrial Technologies
U.S. Department of Energy
Washington. D.C.

The predominant factors affecting the costs of
control technologies are the volume flow of the
methylene chloride-laden airstream, and more im-
portantly,  the  concentration  of methylene
chloride.  Annual vapor emission control costs
have been projected for solvent-laden airflows
ranging from 1,000 cubic feet per minute (cfm) to
50,000 cfm, with  airborne concentrations of
methylene chloride  from 100 parts per million by
volume (ppmv) to 3,000 ppmv. The results of this
study showed that  applications above  500 ppmv
would allow control costs to be kept under $5,000
per ton of methylene chloride controlled.
   The competitive technologies all used adsorp-
tion as a method to remove methylene chloride
vapor from the solvent-laden airstream and con-
centrate it; however, their methods to regenerate
the adsorption bed differed. The three technologies
evaluated were:

    • Adsorption with steam regeneration,

    • Adsorption with inert gas regeneration
     that uses a reverse Brayton cycle
     condensation system, and

    • Adsorption with "decoupled" inert gas
     regeneration that uses a reverse Brayton
     cycle condensation system.
   A "decoupled" inert gas regeneration system
can be physically separated from the adsorption
side of the vapor recovery equipment. Since the
regeneration (desorption) equipment is mobile, it
can be transported from one adsorption con-
centrator to another. Therefore, the cost of the
regeneration equipment is shared among many
adsorption control devices and locations.
   Other technologies that are technically
feasible, such as the destruction of methylene
chloride by incineration, direct condensation of
the vapors from the solvent-laden airstream (using
a reverse Ranklne or Brayton cycle), and off-site
reactivation of adsorbents were screened in the
preliminary stages  of the study  and not found
cost-competitive, under the previously discussed
Competitive Technologies

Adsorption with Steam Regeneration
Figure 1 shows a typical steam-regenerated ad-
sorption system that could be applied to control
methylene chloride emissions. Solvent vapors are
collected on the adsorbent (assumed to be ac-
tivated carbon in this study) and periodically the
adsorbent is regenerated with steam. The equip-
ment consists of a steam boiler, at least two

                                             COOLING WATER

                                                                         AIR STRIPPER
Figure 1.—Steam regeneration system with decanting solvent and water separation.
separate adsorbers (one adsorber is adsorbing
while the other is being regenerated), a blower to
circulate the solvent-laden  airflow  through  the
adsorbers, condenser, separator,  decanting sys-
tem to separate  the steam condensate from the
recovered solvents, and an air stripper to clean the
steam condensate.
    Since methylene chloride is slightly misclble
with water, the decanting process does not remove
it  completely;  however, air stripping takes  the
remaining methylene chloride from the conden-
sate. Then the cleaned condensate can be returned
to the boiler or discharged to the environment. The
air discharged from the stripper is returned to the
adsorbers to prevent discharge of methylene
chloride-laden emissions.

Adsorption with "Coupled" Brayton
Cycle Inert Gas Regeneration

Figure 2 shows an inert (nitrogen) gas regenerated
adsorption system that uses a reverse Brayton
cycle to condense vapors. Solvent vapors are col-
lected on the adsorption bed in the same manner
as the steam-regenerated system; the difference
lies in the length of the adsorption and regenera-
tion cycle of the  adsorbers and in the use of an
inert gas in place of steam. Step-by-step, the inert
gas regeneration  process:
                   • Strips the solvents from the adsorber with
                     hot (above 300°F) inert gas.

                   • Condenses the solvent vapors from the
                     solvent-laden inert gas stream by chilling
                     to extremely low temperatures (-100'F)
                     with a reverse Brayton cycle,  and

                   • Returns the essentially solvent-free hot
                     inert gas to the adsorber for further

                Adsorption with "Decoupled"
                Brayton Cycle Gas Regeneration

                This  method physically  separates inert gas
                regeneration system from the adsorbers. There-
                fore, the equipment components are essentially
                the same  as  those shown In  Figure 2, but the
                adsorbers and the solvent-laden air blower are
                stationed at the emission source and the inert gas
                regeneration system is  mobile  and  can be
                "decoupled" from the adsorbers (see Fig. 3). In this
                way, the reverse Brayton cycle inert gas regenera-
                tion system can serve  many adsorbers  at
                geographically different Industrial sites.
                   The reverse Brayton cycle produces low gas
                stream temperatures by removing heat with a low

                                                                      Reducing Risk In Paint Stripping
Figure 2. — "Coupled" Brayton cycle Inert gas regeneration system (courtesy of Nucon International, Inc.).
                Mobile Regeneration
                                       Solvent Laden Nitrogen Gas
                                      Ho. D,y Nitrogen Gas
                                                                 Carbon   A
                                                                   Bed     (  To Process
                                                                              Not In use
                                                                              while truck Is
                                                                Stationary     regenerating bad
Figure 3.—"Decoupled" Brayton cycle Inert gas regeneration system.
temperature chiller heat exchanger  (heat     the other side of the low temperature chiller again;
regeneration); extracting work energy from the gas     then compressing, and thus  heating, the gas
stream with a turbo-expander to cool it; regenerat-     stream with a turbo-compressor that is driven by
ing heat from the cold gas stream by passing It on     the turbo-expander and a motor-driven vacuum

compressor. The gas stream containing solvent
vapors is cooled significantly enough to condense
a majority of the vapors. Also, it  is heated by
compression to a temperature level (above 300°F)
satisfactory for inert gas adsorption bed stripping
without supplemental heating.
    In the case of methylene chloride, the Inert gas
stream  must be cooled  to  -150eF to remove a
majority (99 percent) of the very low boiling point
solvent. Since the reverse Brayton cycle can reach
a low condensation temperature In a single stage
of turbo compression and expansion. It is a good
method to recover methylene chloride.
    Critical components  of  this system  are two
separate adsorbers with a solvent-laden airblower,
and the reverse Brayton cycle  regeneration sys-
tem, which consists of a dehumldlfler, a motor-
driven  vacuum   compressor,   a   turbo
compressor-expander, a  low temperature chiller
(regenerative heat exchanger), two separators, and
a pump for circulating the recovered liquid solvent.
Vapor Recovery Control
Cost Estimations

The primary influences on the cost of the three
vapor recovery technologies are the volume flow of
the solvent-laden airstream and the concentration
of the methylene chloride within It. For purposes
of evaluation, it was assumed that paint stripping
applications produce airstreams laden  with
methylene chloride solvent concentrations under
3,000 ppmv and the volume flow ranged between
1,000 and 50,000 cfm. Many of the paint stripping
applications have  concentrations under  100
ppmv. However, for applications with very low
concentrations (under 100 ppmv), the cost to con-
trol these emissions by recovery Is exceedingly
high—greater  than $10,000 per ton of solvent
controlled. Therefore, vapor recovery control costs
were  analyzed at  concentrations of 100 ppmv,
1,000 ppmv. and 3,000 ppmv. Table 1  lists key
economic factors  In  the overall cost of vapor
recovery control.

Table 1.—Economic factors assumed to project con-
trol cost for vapor recovery of methylene chloride.
 Methylene chloride recovery
 Solvent-laden airstream time
 Steam cost
 Electricity cost
 Type of adsorbent
 (Dost of adsorbent
 Cost of adsorber structure
 Capital depreciation period
 Interest rate
 Equipment installation factor
$0.25 per Ib. (excludes taxes)

(8 hours per day, 5 days per
 week, 50 weeks  per year,
 2,000 hours/year)
$5.00 per 1,000 Ibs. steam
$0.040 per kw-hr.
Activated carbon
$2.00 per Ib.
$11.00 per Ib. (steam regen.
 made of Hastelloy)
$3.00 per Ib. (both Brayton in-
 ert regen. systems made of
 316L stainless steel)
10 years
10 percent
$20 per CFM of solvent-laden
 volume airflow
    Table 2 summarizes the control cost results of
the study. As you can see, concentrations above
500 ppmv are generally necessary to achieve con-
trol costs below $5.000 per ton. Figure 4 sum-
marizes the regions of applicability for the three
vapor recovery technologies evaluated. The regions
of applicability were made by assuming that con-
trol costs need to be under  $5.000 per ton of
methylene chloride controlled and by comparing
the relative costs of the three technologies.
Table 2.—Control cost for paint stripping with methylene chloride (dollars per year per ton of solvent).
                                               COSTS OF VAPOR RECOVERY CONTROL TECHNOLOGIES
'Cubic feet per minute
"Parts per million by volume

                                                                       Reducing Risk In Paint Stripping
              Volume Flow (CFM)
                             "Coupled" Brayton
                             Inert Regeneration
 "Decoupled" Braytori
 Inert Regeneration

           100      500 1,000  3,000   10,000

         Solvent Concentration (PPMV)
            •Regions of applicability are defined by control costs at under $5,000 per ton
             of solvent and the competitiveness of the technologies to each other.

Figure 4.—Regions of applicability for methylene chloride vapor recovery.
Future Development Needs

The reduction of vapor recovery control costs will
be Impacted by the following critical factors and

    • Production of paint stripping equipment
     that Includes solvent recovery control
     equipment. That Is, every step must be
     taken to get the solvent-laden airflow
     down and solvent-laden air concentration
     up. Of course, the equipment must be
     designed to protect the worker from
     unsafe levels of solvent vapors.

    • Development of a solvent recovery market
     infrastructure that will service many
     industrial users of solvents, such as the
     decoupled regeneration approach.

    • Development of low-cost continuous
     solvent-laden air concentrators (that is.
                           rotating wheel adsorber beds) to increase
                           the concentration of the solvent-laden air
                           downstream of the process but upstream
                           of the fixed bed concentrators. This will
                           allow storage of more solvent on the fixed
                           bed, which therefore, reduces the fixed
                           bed cost.

                         • The ability to fabricate adsorbers out of
                           low-cost materials.

                     The recovery of methylene  chloride from paint
                     stripping applications looks promising if the con-
                     centration level of the vapor stream from the
                     process exceeds 500 ppmv. Paint stripping equip-
                     ment development should be directed at maximiz-
                     ing concentration levels, keeping the safety of the
                     worker in mind.

             Questions  81 Discussion
       Discussion in the question and answer
       periods  of the  maintenance sessions
       focused in large part on the details and
applicability of the many substitute technologies
that were presented. Following the opening ses-
sion, a number of participants commented on the
applicability of different blast media, including
plastic media, to aircraft stripping. There was
some disagreement over methylene chloride's con-
tribution to total toxic organic air releases; Katy
Wolf of the Institute for Research and Technical
Assistance remarked that methylene chloride does
not contribute to photochemical smog. In addition,
there was discussion over whether or not carbon
dioxide  used in CO2 blasting techniques con-
tributed to total emissions of greenhouse gases.
Mike Lewis of Cold Jet, Inc.. noted that the CO2
supplied for blasting is reclaimed as a regenerated
waste gas and as such does not represent  an
additional contribution to greenhouse gas emis-
sions. Paul Soley of Ardrox. Inc., pointed out that
chemical stripping was being associated exclusive-
ly with methylene chloride. He emphasized that
the  chemical Industry is also working on new
chemistries and formulations, such as paint sof-
teners that could be an aid to mechanical stripping
methods in maintenance stripping.
   Following Tuesday afternoon's presentations
on blast  technologies, a short discussion ad-
dressed some of the mechanics of paint removal
using carbon dioxide ice pellet blasting. There was
some difference of opinion over the role played by
thermal shock (contraction of coating due to cool-
Ing) in removing  coatings from the substrate.
H.C.L. Noordermeer of KLM Royal Dutch Airlines
told session participants that the European air-
lines were also facing the problem of what process
to use for coatings removal in the future. He noted
that a task force  of airline representatives and
aircraft manufacturers was reviewing a wide
variety of alternative processes and intended to
formulate guidelines by which airlines could
evaluate  the different stripping processes being
   Wednesday morning's maintenance sessions
Included  more blasting technologies as well as
photo-ablative and laser paint  removal systems.
Discussion after the presentations raised many
questions about the flashlamp/ Infrared and laser
technologies. While heat dissipation was acknow-

ledged as a potential problem for Infrared techni-
ques on aluminum substrates. It was noted that
the technique was very effective on steel structures
or a thicker metal surface that acted as a heat sink.
Dennis Reed of the U.S. Army asked about crack-
hiding problems with blasting techniques that
might smooth over or peen the surface In the
process of removing paint.. Questions were also
raised about the potential for water In high-pres-
sure water blasting to penetrate Into alrframes.
Frank Scharwat  responded  that with the ap-
propriate tools and controls, the process allowed
adequate precision to prevent water penetration.
James Swartz of Northwest Airlines raised the
issue of paint stripping equipment manufacturers
working hand In hand with coatings formulators
to produce a system of paint /paint removal that
would be effective as a coating yet still  easily
removed when desired.
    The final session on Wednesday morning com-
prised presentations  on paint  stripping  waste
management and pollution prevention through
vapor recovery. Discussion Included questions to
Gail Bowers-Irons about the particulars of the
microblal blodegradatlon of paint wastes. Specifi-
cally, discussion  Included questions  about the
ultimate disposition of organic and heavy metal
components of the paint wastes and the effect of
particle size on the effectiveness of blodegradatlon.
John Ogden of General Motors asked what com-
ponents of a system were included in a $28 per
55-gallon drum cost estimate. This cost did not
include capitalization of equipment costs for  a
large-scale system. With respect  to solvent vapor
recovery processes, James Swartz of Northwest
Airlines asked whether the use of solvent recovery
processes would require the operation to obtain a
treatment,  storage, and disposal  (TSD) permit for
treatment  of hazardous wastes. Louis Kovach
replied that if the  solvent is being re-used on site,
it may not  be considered a waste treatment sys-
tem. Willie Smith of McGean-Rohco. Inc., noted
that with paint strippers for aircraft, it is unlikely
that the product you get through vapor recovery
will be re-useable in that state for repeated paint

Current Paint Stripping Practices
              Chair: Sandra Eberle
          Directorate for Program Management and Budget
           U.S. Consumer Product Safety Commission

              Chair: Glenn Simpson
             Directorate for Economic Analysis
           U.S. Consumer Product Safety Commission

Current  Practices  and  Processes for
Paint  Stripping  in Professional  Furniture
Tim B. Inman
Mlnuteman, Inc.
Waterloo, Wisconsin
The Roll of Stripping in a
Commercial Operation

The roll of stripping In a commercial service opera-
tion has changed markedly In the past decade. At
the end of the 1970s and Into the beginning of the
1980s, many so-called "strip shops'" existed. Their
function was purely utilitarian; they stripped old
layers of paint and varnish from furniture brought
to them by hobbyists and treasure hunters. Pieces
came Into the shops from the auction block, the
attic, the basement, or the barn loft.
   A happy convergence of events drove this "an-
tique" hunting passion: Celebration of the Bicen-
tennial, national turmoil, the back-to-the-earth
movement, and no-budget baby-boomers setting
up housekeeping and being willing to use second-
hand furniture. At the same time, a chrome-and-
plastic throwaway attitude In the new furniture
markets created a demand for familiar and solid
furnishings at reasonable prices.
   Thus, initially probably 90 percent of the strip
shop business was just stripping. Customers
would take the cleaned pieces home and apply the
stain and varnish coats themselves. As the novelty
wore off, and as the appeal of the "homemade"
refinlshlng look faded in a more affluent period,
furniture stripping shops began to hear requests
for more complete services.
   Today, the market has changed to the point
that the percentages of work have nearly reversed
themselves, with almost 95 percent of the furni-
ture entering a shop for the full treatment. Only
about 5 percent is there Just to be stripped clean
and made ready for the customer who will do the
final finishing work.
New Products for Stripping

Just as the mix of activity has changed during the
past decade, so has the profile of the  furniture
Items being brought into the shops for service.
Earlier,  solid wood Items like oak chairs and
tables, maple Shaker stands,  and the massive,
solid walnut and mahogany Victorian  furniture
made up the bulk of the work. Currently, Interest
is focused more on the delicate veneers and inlaid
pieces showing  the Art Deco influence of the
1920s. The smaller, more highly styled pieces are
quite popular.
   The condition of the objects has also changed.
Where once no Item was considered for refinlshlng
if it needed  much repair at all. It is now not
uncommon to restore furniture that has been
severely broken and damaged. Where once only
solid wooden articles were refinished, now multi-
ple materials, like leather inlays, metal and ivory
boule. and exotic matched veneers are common.
Processes Typical in
Commercial Shops

Types of Equipment
Essentially two processes are used to remove un-
deslred coats of old finish In all shops: chemical
removal and mechanical removal. Nearly all
professional furniture stripping operations maxi-
mize the use of chemical removal methods.
Mechanical  elimination of finish from furniture
has not thus far proven to be both effective and
nondestructive to the fine wood substrate.

   Within the bounds of the chemical process,
there are three common methods of applying the
various solutions: (1)  by hand (typically with a
brush); (2) through a pumping system (typically
with a hose and brush): or (3) by immersion (in
   It is interesting to note that it has been the
delivery device—the brush, the pump, or the vat—
that  has received the greatest attention in the
marketplace. Salespersons  make extravagant
claims for the type of equipment they are selling.
Actually, the chemical the device delivers is the
important element. Until very recently, this fact
has  received almost  no attention. The  brush
doesn't strip, nor does the pump or the vat; the
chemical, not the delivery device, determines the
success of the process.
   Efficiency dictates that commercial furniture
shops use either vats or pumps to deliver stripping
chemicals to the work surfaces. Pumping systems
are the most commonly found among the shops by
a large margin of four to one over vat systems.
    Pumping systems are very Inexpensive to
make; a motor, a pump, a length of hose, and a
brush are all that are needed to devise a functional
system. Commercially assembled  pumping sys-
tems are superior in design  and easily shipped.
Pumping systems also require almost no  ex-
perience or training to be used successfully.
    Immersion vat systems are also simple tech-
nology, but they are much more expensive and
cumbersome to make. Costs of keeping vats
charged  with chemicals are  higher than in any
other system. Many  refinements have been  ac-
complished over the years to make commercially
designed vat systems superior to  home-made
units, but vats  are the most expensive pieces of
equipment  to transport. Immersion vat systems
also require the most training and experience to
be used to their full advantage.

Types and Quantities  of Chemicals

Until the early  1970s, benzene was the solvent
used to strip chemicals. It is both flammable and
toxic. After its health safety risks became known,
benzene was replaced as a stripper by methylene
chloride products. Nonflammable,  Infinitely safer
than benzene,  and quite effective, these com-
pounds have been used successfully ever since.
    Methylene chloride, by itself, is not the best
paint remover. It must be  spiked with activating
agents to produce the most powerful  results.
Acids, alkalies, amines, and phenols are used for
this  purpose. Wetting agents  also help reduce the
surface tension and hence further Improve the
penetration.  Thus, the explosion of different
removers on today's market—each claiming to be
better than the rest.
   Methylene chloride is also usually the single
most expensive component In the  remover for-
mulas, often by a factor of four to one. Thus, there
is a tremendous incentive to make the product
cheaper by adding less  expensive diluent com-
ponents like  alcohols, toluene, xylene,  acetone,
simple mineral spirits, or even water. Usually this
not only reduces the efficacy of the product but
also, depending upon the compound used, adds
health or flammability hazards—or both.
   Brushing applicators and  pumping system
users are usually limited to  solvent removers.
Immersion vat operators may use water-based
strippers in addition to, or in place of, solvent
applications. Vat operators historically have used
hot water  and lye. The combination Is cheap,
effective, and has been recommended In furniture
refinlshlng guides. Despite these facts, lye will,
unfortunately, damage furniture. Lye will attack
anything  organic, including wood,  glue,  and
veneer. Nevertheless, It continues to be used In
some shops.
    Far superior water-based stripping com-
pounds have been available on  the market for
many years. These complex alkaline compounds
effectively remove many of the older finishes that
solvent  removers like methylene chloride  find

Quantities of Solvent Removers Used

Most people  engaged In removing solvents use
pumping  systems,  and this  process uses the
largest quantity of solvent removers. Many of these
operators use In excess of twelve 55-gallon drums
of product each  year.  By Its very nature, the
pumping process creates the greatest surface area
exposure and hence has the highest evaporation
rate (and operator exposure) In the Industry.
    Despite the fact that pumping systems are the
most common and least expensive process, they
are not the most effective paint removers.
    Immersion vat systems often use both water-
based alkaline removers and solvents. They cur-
rently represent the smaller percentage of market
share. However, vat systems are much more effi-
cient in their use of solvent removers. While many
pumping systems use In excess of twelve 55-gallon
drums per year, few vat operations consume more
than four to six 55-gallon drums per year, or about
one-third  to  one-half of the  consumption  of a

                                                                      Reducing Risk In Paint Stripping
pumping system operator. The market dilemma
from the chemical supplier's point of view should
be apparent.
   Further, vat system operators using proper
techniques and equipment are usually exposed to
less remover vapors and use far less remover per
item than in any other system. Because of their
ability to hold the stripping chemistry in intimate
contact with the finish surface without being sub-
ject to evaporation, vats are also the most effective
delivery vehicles. Vat systems can offer superior
performance as well as superior exposure and
consumption characteristics.
Types of Coatings

As furniture degrades, it is abused. The profes-
sional furniture stripper encounters all types of
paint and finishes including fine French polish,
varnish, interior kitchen enamels, exterior house
paints (lead and mozzarella), floor enamels, and
marine finishes.  Sometimes several finishes are
removed from a single piece—for example, John
Deere green Implement enamel (farm tractor paint)
has been found on a marble-topped Victorian wal-
nut table.
Special Concerns

All of the ordinary business considerations face a
commercial stripping operator: overhead,  time,
labor, and so forth. But a professional furniture
restorer also has some special concerns that con-
trol  and narrow the selection of equipment,
chemistry, and techniques. Hidden below layers of
paint is a substrate of unknown description. This
may be veneer, solid wood, plastic, or metal. The
substrate may be in good shape, or it may be ready
to fall into pieces. All too often, a piece that would
be considered "Junk" becomes  much more valu-
able following restoration.
    Like  a physician, the  professional furniture
restorer seeks first to do no harm. A very special
concern  is  care  of the wooden skeleton hidden
beneath layer-after-layer of grafted skins of paint.
It is bad practice to experiment with unknown and
untested chemistry at the risk of damaging the
unknown substrate.
    In addition, the workplace and personal safety
must also be carefully considered. It is not worth
Jeopardizing health and safety for  the sake of
salvaging an auction find.  In addition  to the
workplace, the  broader environmental  issues
must also be taken into consideration with safe
disposal of wastes and toxics. Handled thoughtful-
ly, no solvent need ever be dumped. By using a
properly formulated blend, solvent removers can
be continually reclaimed and reused. The  paint
solids, consisting mostly of gums and resins, can
be effectively removed and disposed of dry. It is the
same paint that would have been thrown away had
the whole furniture piece been discarded. Of
course, as a result of the stripping, the paint is
collected and  concentrated.  This should make
handling and containment efforts much simpler.
Happily, there Is as much economic incentive for
the commercial operator to reclaim and recycle the
solvents as there Is environmental rationale.
   Reducing air exposure concentrations has not
received the attention it deserves. Hopefully, with
the passage of the Clean Air Act, this will now
change. The many Improperly designed, installed,
or used pumping systems for stripping represent
a tremendous air contamination source for both
the operator and the environment. Designing bet-
ter air handling systems, encouraging more use of
vats and "passive" application devices, and
developing better evaporation-retarding chemistry
will address this problem. Unfortunately, the com-
mercial interests of solvent suppliers  mitigate
against the aggressive marketing of less dangerous
vats, since they can often sell two to three times
as much product to pumping system operators
than they can to Immersion vat users.
   A final issue is flammability. Because of
methylene chloride's nonflammable quality, fires
in commercial shops using a methylene chloride
product professionally designed for the purpose
have not been common for many years. Previously,
when benzene was used, fires were the leading
cause of injury. If today's volume of stripping was
done with flammable products like acetone, lac-
quer  thinner, benzene, or some of  the  newly
proposed flammable methylene chloride alterna-
tives, this risk would Increase enormously.

Furniture stripping has become a very safe oc-
cupation for both  the  operator and the work
product. More  furniture Is being restored and
reused  today than ever before. Thousands of
workers are actively Involved. Including the hand-
icapped in special workshops. Millions of pieces of
furniture have  been given a new lease on life.
Exotic lumber and cabinetry have been preserved
for the enjoyment of generations yet to come, and

the strain on forests to constantly produce more
wood has been eased.
    When  accidents have occurred,  there have
usually been contributing factors such as Inten-
tional misuse. Equipment and workplaces can be
made even safer and more accident free. Equip-
ment design, chemistry formulation, and worker
technique all need to be addressed.
    Regardless of the toxicological aspects of
methylene chloride, there are no products  avail-
able to the industry that are as effective, safe, and
fire resistant as this substance. It is hoped that,
in the zeal to further reduce the very small risks
associated with paint removing, more hazardous
situations are not Inadvertently created.
    Several suggestions should be considered to
Improve safety and health aspects  of the paint
remover Industry. These are:

    • Follow the European lead and encourage
      the use of vat and more passive
      application systems. Minimize exposure
      by limiting surface area exposure. Explore
      alternatives but do not condemn a proven
      product too quickly; the alternatives may
      prove to be worse.

    • Reduce the all-or-none rhetoric in the
      methylene chloride battle. A
      middle-ground compromise may be a
      much more fruitful approach to the
     problem. Instead of a one-step process, a
     multi-tiered approach should be
     implemented. Methylene chloride or the
     alternative solvent removers can be used
     where they are needed'and work best, as
     appropriate. For example, buttermilk
     paint strips best under contact with a
     water-based alkaline material.
         With this approach, the newer, more
     solvent-susceptible layers of unwanted
     finish are removed by Immersion in a
     methylene chloride stripper. Lower layers
     that do not respond well to this solvent
     should be removed with one of the
     alternative strippers. This system not only
     produces less chemical exposure, It
     results in a superior work product.

   Care should be taken not to encourage well-
meaning but unsuspecting people to buy cans of
untested products that proclaim on the outside
when in fact they contain substances that  are
more dangerous.  Citizens, as  well  as  policy
makers, want to believe that a magic new technol-
ogy can  solve all problems; unfortunately,  not
magic, but patience and careful consideration of
available options are required to reduce safety and
environmental risks in  the  paint stripping In-

Do-it-yourself  Paint Stripping Practices
The Household  Market
Mark A. Monique
Savogran Company
Norwood. Massachusetts

The do-it-yourselfer typically purchases paint
strippers for relatively small jobs, such as restor-
ing furniture or reflnishlng wood surfaces. Judging
from estimates based on calls to Savogran's toll-
free 800 Information number, the majority of con-
sumers who use paint remover—85 percent—strip
furniture; the remaining 15 percent strip interior
and exterior woodwork,  metallic items, and
masonry surfaces.
Typical Coatings

A number of different kinds of paint and finishes
are used In and around the home. From the do-it-
yourselfer's perspective,  they can be divided
generically Into two groups:  enamels and clear

A pigmented finish designed to produce a smooth.
hard coating, enamel is easily cleaned and highly
resistant to weather and wear. Enamels are avail-
able for both interior and exterior use. Commonly
used binders In enamel finishes include the follow-
ing resins:

   • Alkyds: Alkyds are a group of synthetic
     resins  that generally possess excellent
     drying properties combined with flexibility
     and durability.

   • Linseed Oil:  Linseed oil  Is a durable,
     medium-gloss resin used largely in house
     and trim paints. It Is also  an Important
     modifying oil in synthetic alkyds.
   • Latex: The  most common latex paints,
     acrylic and  vinyl, are sold In high-gloss,
     semi-gloss, or flat finishes. Latex paints are
     durable and weather well.

   • Epoxy: An  epoxy coating system has
     exceptionally  good adhesion  and is
     resistant to water and mild chemicals.

Clear Finishes

Unlike paints, clear finishes are pigment-free and
therefore do not hide surfaces. However, because
they do not contain pigments, clear finishes do not
stand up to sun and weather as long as enamels.
The predominant clear finishes are:

   • Varnish: A  clear, solvent-thinned  finish
     used on wood surfaces, varnish is generally
     resistant to moisture and wear.  Spar
     varnish is used for exteriors and boats;
     catalyzed varnishes provide a protective
     finish on kitchen cabinets.

   • Shellac: A clear finish made by reducing
     natural  resins  in alcohol, shellac dries
     rapidly and is often used as a sealer to
     prevent bleeding from wood or as a final
     finish on furniture.

   • Lacquer: A fast-drying finish that contains
     nitrocellulose, lacquer is used primarily on
     furniture. It produces a water white finish
     that emphasizes the natural wood grain.

   • Polyurethane:  Polyurethane Is  a clear
     finish that is used as a protective coating on
     furniture,   interior   woodwork,  and
     hardwood floors. It is extremely durable and
     can be modified with an alkyd.

Paint Stripper Application

The  do-it-yourselfer  generally  applies  paint
remover with a natural bristle brush. Coverage
and number of applications depend on the type
and numbers of layers of coating. For methylene
chloride formulations, coverage varies from 50 to
100 square feet per gallon and time to lift the paint
from  15 to 30  minutes. For non-methylene
chloride formulations, coverage is generally 15 to
25 square feet per gallon and time to soften paint
from 30 minutes to 30 hours. Methylene chloride
removers are laid in one pass—not brushed—onto
the surface by working in one direction and apply-
ing remover to about two square feet at a time.
Since non-methylene chloride formulas have low
evaporation rates, the stripper is laid onto the total
area to be stripped.
    When testing shows that the remover has done
its work,  the resulting sludge is removed by a
gentle scraping with a dull putty knife. On carved
or grooved surfaces, use an old toothbrush or
coarse twine. After removing the bulk of the
sludge, wipe away remaining residue with mineral
spirits (or a detergent solution if using the water-
wash method).
Consumer Concerns

Consumers are increasingly more concerned
about product hazards, costs, and effectiveness.
Unfortunately, hazard and cost are two competing
criteria. Manufacturers can stop using methylene
chloride in  solvent-based products, but  costs,
stripping times, and flammability will all increase.
In addition, consumers have reacted negatively to
slower-working dibasic ester (DDE) formulations.
Their need for a faster-acting product seems to
outweigh hazard concerns.
    There is a point at which the cost of a gallon
of paint remover  becomes prohibitive, as ex-
emplified by N-methyl pyrrolidone (NMP) formula-
tions  that  have  a raw material  cost  of
approximately $12 per gallon. A typical NMP for-
mula has a suggested retail price of $10.31 per
32-ounce container, which provides retailers with
a  39 percent margin,  while  representative
methylene chloride removers cost $7.16 per 32-
ounce containers,  giving retailers a 55 percent
margin. Consumer costs for paints are also  af-
fected by the two-step distribution system, which
adds to the final retail selling price.
    Remover effectiveness encompasses certain
application characteristics. Manufacturers have
investigated using amines as possible activators,
but many amines stain wood. Although removers
should not corrode metal or raise the grain of the
wood,  many  non-methylene chloride formulas
contain water, which  affects  fine woods and
veneers. Also, removers should  not  require
neutralization or have an objectionable odor.
Paint Stripping  Formulations

Paint strippers can be liquid, heavy-bodied, or
semi-paste, depending on the Intended applica-
tion. In general, liquids work best for Intricate and
flat horizontal surfaces. Heavy-bodied and semi-
paste strippers cling,  making them Ideal for Ir-
regular surfaces.  Removers are also water
washable or solvent washable. The water-wash
method works well but tends to raise wood grain
and loosen glued veneers. Solvent rinses are basi-
cally problem-free.
    Chemical composition also dictates formula
parameters. Slower-working, low vapor pressure
formulas such as  the DBE must be thickened to
stay on the surface and penetrate the paint film.
Because they act quickly, methylene chloride for-
mulas can be made In  a variety of viscosities. The
following groups of removers are  based on the
major active ingredient(s) In the formulas.

    • Nonflammable  Methylene Chloride: This
      formula generally contains greater than 75
      percent methylene chloride and  5 to 15
      percent methanol, ethanol. isopropanol, or
      a combination of the three. Some formulas
      use mineral spirits to reduce raw material
      cost.  The formula is thickened  with a
      cellulose thickener. Includes paraffin wax to
      retard evaporation, and may also contain
      detergents to make It water  washable and
      activators such  as potassium oleate.
         The nonflammable methylene chloride
      formula is the strongest and most efficient,
      and  the only  one that removes tough
      finishes such  as catalyzed varnishes.
      epoxies, and baked enamels. Lastly, be-
      cause of the high methylene chloride con-
      tent, the products are nonflammable.

    • Flammable Methylene Chloride:  This
      formula generally contains 15 to 20 percent
      methylene  chloride,  20 to 25  percent
      methanol, 35 to 40 percent toluene, and 20
      to 25 percent acetone. Mineral spirits may
      be used in place of a portion of the toluene
      to comply with non-photochemically
      reactive requirements in states  such as
      California. The formula may also Include a

                                                                Reducing Risk In Paint Stripping
  cellulose thickener, paraffin wax to retard
  evaporation, and detergents to make the
  composition water washable.
      This formula is effective on lacquers and
  shellac because of the high acetone and
  methanol levels,  and also  works well for
  short-oil alkyds because of the high toluene
  level. The raw material cost is one of the
  lowest, comparable only to the flammable
  non-methylene chloride formulas,  which
  are less efficient.

• Flammable Non-methylene Chloride: The
  formula generally contains acetone,
  methanol. toluene, and mineral spirits, with
  percentages  varying between manu-
  facturers   depending   on   formula
  parameters. Acetone levels are controlled to
  keep the flash point acceptable, and toluene
  levels  must be  under  20 percent for
  products sold in California. Acetophenone,
  which  has  a strong odor, is  sometimes
  added  to improve efficiency. The formula
  may  include a  cellulose  thickener
  (depending on application), a paraffin wax
  to retard evaporation, and detergents to
  make the composition water washable.
      This formula is effective on the same
  type of coatings  as flammable methylene
  chloride, but may work slower. The flash-
  point is generally lower than that of flam-
  mable methylene  chloride.

• Powdered Caustic  Removers:  These
  removers  generally contain  sodium
  hydroxide, fillers, and  thickening and
  wetting agents. Products are mixed with
  water to form a paste and applied in a heavy
  coat. This formula works slowly and is not
  effective on latex paints. Sodium hydroxide,
  which irritates eyes and skin, will darken
  some types of wood and may raise the grain.
  Caustic removers work well on old milk

• Furniture Refinishers: Formulas currently
  on the market are similar to  the solvent
  composition  of flammable  removers.
  Furniture refinishers, which never contain
  thickeners  and may not  include wetting
  agents, work only on clear finishes and are
  used in conjunction with steel wool. Some
  refinishers contain methylene chloride.

• Dibasic Ester Removers: DBE, which is a
  blend of dimethyl adipate. dimethyl
  glutarate,  and  dimethyl succinate,  is
      emulsified in water and thickened to make
      a paint remover. Wetting agents  are also
      added to improve penetration through the
      paint film. DBE has a vapor pressure below
      0.2mm Hg at 20°C, which helps keep the
      remover wet for extended periods.  DBE
      removers have no objectionable odors and
      are  considered somewhat safer than
      conventional removers; however, they work
      much slower and usually cost considerably
         Users of DBE have reported  cases of
      blurred vision, which are  being inves-
      tigated. Consumers, who are accustomed to
      the almost immediate result of conventional
      removers, must be educated to use DBE,
      which Is applied in a heavy coat and left to
Consumers Product Safety
Council Labeling Requirement

The Consumer Product Safety Council labeling
requirement for products containing methylene
chloride, combined with better point-of-purchase
material that describes important stripping con-
siderations such as worksite  selection,  setup,
cleanup, safety, and health effects, appears to be
having a positive effect on the way consumers use
paint removers. Consumers are not deterred from
buying the products, and, with this information,
now use them more responsibly.
Recent and Future

One of the most recent developments in household
paint strippers has been the introduction of a new
NMP formula. However, the estimated price for the
NMP formula Is $50 per gallon, whereas the typical
nonflammable methylene chloride remover retails
for approximately $20 per gallon.
    Other solvents suggested as  possible
methylene chloride  substitutes because of their
desirable properties such as low toxicity,  high
flash point, and high solvent activity Include:

    • Furfuryl Alcohol: A member of the family
      of heterocyclic compounds known as the
      furans, furfuryl alcohol reslnifles (converts
      to resin) violently in the presence of strong
      acids. Furfuryl alcohol has an objectionable

      Propylene Glycol Ethers: These ethers are
      Ineffective paint strippers. Propylene glycol
      monomethyl  ether  acetate  shows some
      potential as  a cosolvent  In stripper

      G-Butyrolactone:   This   heterocycllc
      chemical has similar properties  to NMP,
      including high cost.

      Propylene Carbonate: This chemical has
      been suggested  as  a methylene chloride
      substitute because  of its success  in the
      electronics industry.  It Is an Ineffective
      paint stripper.

      Trioxane: Trloxane, which Is an anhydrous
      cyclic trlmer of formaldehyde, can sublime
      to produce flammable vapors. Trloxane is a
      crystalline solid that must be dissolved in a
      cosolvent. When the cosolvent evaporates
      from the substrate, trixane recrystalllzes.
      The solid has a flash point below 1.0"C.

      Ethyl-3-Ethoxyproplonate: A linear mole-
      cule that has limited stripping abilities.

      Dimethyl Sulfoxlde: This chemical has an
      extremely objectionable odor and  limited
      stripping abilities.

      Cyclohexanone: A ketone with high flash
      point  and  limited  solvent activity,
      cyclohexanone has exhibited potential as a
      cosolvent In stripper formulations.
   •  Methyl-N-amyl Ketone: This chemical has
      a strong odor and limited solvency.

   •  Alkyl Acetates:  These chemicals have a
      strong odor and limited solvency.

   These compounds have been Investigated In
different  combinations  and with many types of
possible activators. No synerglsm equals the per-
formance of methylene  chloride. The parameters
under which stripper formulation testing Is per-
formed are important. Certain stripper  formula-
tion data can be misleading; for example, data can
vary with the length of time paint panels are dried.
Formulating a cost-efficient  formula Is difficult,
because  the raw material cost for these com-
pounds Is three to eight times more than the raw
material cost of methylene chloride.
   Future developments should Include products
that  exhibit low toxlcity, blodegradabillty, non-
photochemical reactivity, low volatile organic con-
tent, efficient  paint  removal, and flash points
above  100°F. Savogran has  developed  products
that meet all these criteria with the exception of
efficient paint removal at room temperature. How-
ever, to match the efficiency of methylene chloride
formulations, the product must be heated, which
is unacceptable for  the  consumer market  but
tolerable for most industrial applications. (The
high cost also makes these products much more
acceptable for the Industrial market.) While many
efficient  paint stripping products are available,
technology has not progressed to the point where
manufacturers can produce a cost-effective  for-
mula that meets the consumer's expectations.

Comparative  Performance of Substitute
Paint Stripper Formulations
Janet C. Hickman
The Dow Chemical Company
Midland, Michigan
       Chemical suppliers are continually chal-
       lenged to develop safer, more cost-effec-
       tive chemicals for any given application.
including paint strippers for household and com-
mercial furniture reflnlshlng. Methylene chloride
is presently the primary solvent used In chemical
stripping formulations. Concerns about potential
health effects associated with using methylene
chloride have, over the past few years, led to a
renewed search for alternative solvents. This paper
describes a test procedure that Dow Chemical has
used to screen paint stripper formulations and the
results of those tests. It also provides additional
perspectives on issues that must be considered as
industry works to develop new paint-stripping for-

 The Ideal paint stripper would have three major
 characteristics: good performance, a good safety
 and health profile, and low cost. However, In reality
 the choice among existing products requires con-
 sidering a series of trade-offs to gain the greatest
 total benefit for the Job at hand. The next genera-
 tion of paint stripping formulations must meet new
 needs; to accomplish this goal, It Is necessary to
 understand how the formulations currently used
 were developed.
   The development of today's  highly efficient
 paint strippers has a long history, dating to the
 early twentieth century  when Carlton Ellis and
 Boris Lougovoy patented numerous formulations.
 Ellis is further credited with developing nonflam-
 mable strippers to replace such solvents as ben-
 zene, toluene, acetone, and ethanol, which were
 commonly used at that time. Kuentzel and Liger
reported their evaluation of the relative stripping
power of numerous chlorinated solvents in 1947.
Berkeley, Schoenholz. and Sheehy expanded upon
this list In 1955. Concurrently, the introduction of
more chemically  resistant coatings made the
search  for solvents that  would  work effectively
more difficult. It was through the research efforts
of these and many other people that the wide use
of methylene chloride as the primary component
of paint strippers for  both industrial and
household applications evolved.
   Methylene chloride based-furniture strippers
currently used generally consist of the  com-
ponents listed below. While exact formulations
vary, each component has a specific function:

   • Methylene  chloride:  This Is the active
     Ingredient  that penetrates the coating.
     Because of its relatively high evaporation
     rate, once through the coating, the vapor
     pressure generates blisters and lifts the film
     from the substrate.

   • Paraffin wax: This wax retards evaporation,
     forming film on the surface. It contains the
     toxic substance toluene as a solvent for the

   • Celluloslc thickener: The thickener holds
     paint stripper on vertical surfaces. While a
     thickener is often used In formulations for
     consumer use, it may or may not be used in
     commercial strip shop formulations.

   • Methanol: This  Is the active ingredient, as
     well as solvent, for the thickener.

   • Mineral spirits: The spirits keep the paint
      film wet.

Defining  Performance

There are several criteria that define good perfor-
mance. A paint stripper must work on a number
of different surfaces, to remove a variety of dif-
ferent coatings. Particularly when reflnlshlng old
furniture, several layers of different kinds of coat-
Ings may have to be removed, adding another level
of complexity.
    Speed and ease of removing the coating are
also Important to the end user. For example, an
extremely good solvent for  the coating may not
provide the most desirable remover if the solubil-
Ized coating redeposlts on the substrate, making
additional treatments necessary. From  a strip
shop  operator's standpoint, this  could also be
undesirable, because the formulation  would
rapidly  become  contaminated, decreasing the
number of pieces that could be stripped  with a
given volume  of formulation. Finally, the formula-
tion (or the technique) must not harm the sub-
strate, and must not adversely affect the ability to

The  purpose of this study  was to establish a
laboratory method for screening the performance
of paint stripper formulations in a uniform.
measurable manner.
   Thirty-nine paint stripper formulations were
tested for this purpose. These formulations con-
sisted of commercially available products, as well
as formulations prepared In the laboratory from
literature references. The formulations are defined
as completely as possible In Tables 1-4, although
specific product names have been deleted. For
ease  of reference, the formulations  have been
grouped In categories according to components
used in the formulations. "Traditional formula-
tions" are  those  containing methylene  chloride
and/or other standard solvents such as aromatic
hydrocarbons, alcohols, and ketones. "NMP For-
mulations" are those containing standard solvents
blended with AT-methyl pyrrolldone. "Ether/Ester
Formulations" contain  those materials  blended
with   standard    solvents,    and   the
"NMP/Ether/Ester Formulations" represent mix-
tures of all the above materials.
   Boards of oak, maple, and pine were chosen
as representative  of open/closed grain hard/soft
wood substrates. The boards were sanded and
cleaned with a tack cloth. Each board was divided
into  five equal sections using masking tape. Two
coats of a representative coating were then applied
to the unique sections of the board, allowing two
days cure time followed by light sanding and clean-
ing with a tack cloth between coats. The five
coatings used were the following: an alkyd enamel,
latex semigloss enamel, flat acrylic latex, spar
varnish, and urethane varnish. Both sides of each
board were prepared in the same manner.
    One side of the board was stripped two weeks
after coating, the other six weeks after coating. All
coatings were more difficult to remove after six
weeks. Further, early tests Indicated oak to be the
more difficult substrate. Therefore, only strippers
that performed acceptably on the maple and pine
screening were tested on oak. Polyurethane var-
nish was the most difficult coating to remove.
Again, only those formulations that showed good
performance on the first four coatings were actual-
ly tested on the polyurethane varnish.
    The stripping tests were conducted as follows:
Prepared and cured boards were divided into one-
inch segments, again using tape. Five drops of
stripper were applied per square inch. An even
scrape was applied using a .25-Inch spatula on the
surface every 10 seconds  until bare wood was
observed.  The time taken  to strip the  coating
(observe bare wood) was then recorded. With the
exception of trying to remove urethane varnish, an
individual test was suspended after five minutes if
the coating could not be removed.
Results and Conclusions

The data from the tests performed after a six-week
cure are shown  in Tables 5-8. Figures 1 and 2
summarize the data for all formulations in order
of observed  performance for all coatings except
polyurethane varnish. The performance data on
polyurethane varnish are summarized separately
in Figure 3.
   As a group, the traditional formulations out-
performed all other groups of formulations in this
screening test. A second tier of performance, those
formulations taking an average of approximately
1.5 minutes to strip most coatings, was observed.
Performance of this group appeared to  depend
more on the concentration of solvents such as
toluene and xylene in the formulation than the
choice of alternative solvents.  The poorest per-
formers were those formulations that not only did
not include methylene chloride, but also did not
Include toluene or xylene.
   A similar trend for the traditional formulations
can  also be seen for  relative performance on
polyurethane varnish. It is interesting to note that
formulation  number 7, which contains a high

                                                                                          Reducing Risk In Paint Stripping
Table 1.—Traditional formulations for paint strippers.
                                                                      FORMULATION NUMBER
COMPONENT % BY WEIGHT                    1234
Acetone                                                       20                  19.7       22.2                  13.1
Acetophenone                                                                                           55
Alkyl acetates
Amines                                                                                                             13.4
Aromatic blend
Cellulosic                                    1.2                          1.5                              1.5
Dibasic esters
Diethylene glycol n-butyl ether
Ethylene glycol n-butyl ether
Methanol                                    7.8       15                19        26.6       22.2       19         43.9
Methyl amyl ketone
Methyl ethyl ketone
Methylene chloride                          81.1        70      60        55        38         22
Mineral spirits                                6.2
Mixed glycol ethers
Propylene carbonate
Propylene glycol methyl ether
Propylene glycol methyl ether acetate
Toluene                                     2.1        15      20        23.5       15.1       26.1       23.5        27.9
Unidentified                                                                         0.6        6.4                   1.7
Wax                                        1.6                          1.5                              1.5
Table 2.—N-methyl pyrrolldone formulations for paint strippers.
                                                                      FORMULATION NUMBER
COMPONENT % BY WEIGHT	9	10	11	12	13	14	15	16
Alkyl acetates
Amines                                                                                                   10        10
Aromatic blend                                                                                            45        45
Cellulosic                                    1.5
Dibasic esters
Diethylene glycol n-butyl ether
Ethanol                                                           20                  40
Ethylene glycol n-butyl ether
Methanol                                   19
Methyl amyl ketone
Methyl ethyl ketone                                                           20                  40
Methylene chloride
Mineral spirits
Mixed glycol ethers
N-methyl-2-pyrrolidone                        55          50        40        40        30        30        45       45
Propylene carbonate
Propylene glycol methyl ether
Propylene glycol methyl ether acetate
Toluene                                     23.5
Wax                                         1.5
Xylenes                                                 50        40        40        30        30

 Table 3.—Ether/Ester formulations for paint strippers.
                                                                     FORMULATION NUMBER
 Alkyl acetates
 Aromatic blend
 Dibasic esters
 Diethylene glycol n-butyl ether
 Ethylene glycol n-butyl ether
 Methyl amyl ketone
 Methyl ethyl ketone
 Methylene chloride
 Mineral spirits
 Mixed glycol ethers
 Propylene carbonate
        20          42    42    33

        30    25    25    25    33
                                                    1.5     1.5
      18    18

20    42

                                       50    48
                                       30    40
                       19       19     19
Propylene glycol methyl ether
Propylene glycol methyl ether acetate

23.5 20 15 15 15 34










 Table 4.—NMP/Ether/Ester formulations for paint strippers.
                                                                    FORMULATION NUMBER
 Alkyl acetates
 Aromatic blend
 Cellulosic                               1.5
 Dibasic esters
 Diethylene glycol n-butyl ether                    20
 Ethylene glycol n-butyl ether
 Methanol                               19
 Methyl amyl ketone
 Methyl ethyl ketone
 Methylene chloride
 Mineral spirits
 Mixed glycol ethers
 N-methyl-2-pyrrolidone                   27.5     40
 Propylene carbonate
 Propylene glycol methyl ether             27.5
 Propylene glycol methyl ether acetate
 Toluene                                23.5
 Wax                                    1.5
 Xylenes                  	40




                                                  21.8   27.2   22.9
                                                  22.7   22.4   23

40     30     28.7   21.3    28.2    17.9

20     40                           40.3

              26.8   29.1    25.9

40     30

                                                                             Reducing Risk In Paint Stripping
Table 5.—Performance of traditional formulations (after a six week cure).
















Table 6.—Performance of N-Methyl Pyrrolldone formulations (after a six week cure).





















Table 7. — Performance
of Ester/Ether formulations (after a six week cure).































          1  5  2
                 7 3 34 6 14 25 20 13 21 35 12 26 18 30 29
                  FORMULATION NUMBER
                            I ETHER/ESTER CD MIXTURES
                                                                 TIME (MINUTES)
                                                                   11  9
             23 10 31  17 24 33 27 22 16 15 32 28 38 36 37 39
                  FORMULATION NUMBER
                                                                    I TRADITIONAL
                                                                                        I ETHER/ESTER  I	I MIXTURES
 Figure 1.—Stripping performance on all woods and
 finishes except urethane.
Figure 2.—Stripping performance  on all  woods and
finishes except urethane.

                                                               Reducing Risk In Paint Stripping
Table 8. — Performance
of NMP/Ester/Ether formulations
(after a six week cure).

16 11
14 1
4 ~jl ^njdunffllfi








*«i III
ill III






1 4 5 6 23 8 3 12 14 2 13 10 11 34 7 25 18 29 28 28 19 20 21
Figure 3.— Stripping performance on urethane varnish.

percentage of acetophenone, was not
AfVWM^i.aA ._._ A.1— J 	 ..... _ A.l__ ^ 1W1A.1— 4.1 	


0.67 3 6.33
0.67 2.17
0.67 2.83
1 3.83
0.67 2.83
0.5 1.5 4.67
0.67 2.67
1.17 5
1 5
1 5
2.67 3.83

0.83 2.17
1 2.1
0.83 3
1 4.17
0.83 4.83
0.83 2 4.67
1 3.17
1.83 5
2 5
1.33 5
1.67 4.17

0.67 4.5 7.33

1 5

1 4.83
0.67 4 4.67

mulatlons appeared to be the poorer performers
on polyure thane.
Overall, formulations 1 , 4. 5. and 6 consistent-
ly out-performed all other formulations on all sur-
faces and coatings tested. It Is Important to note
that the concentration of methylene chloride In
these formulations ranges from 22 to 81 percent.
I*VIAQA /latci uffMilH tjAYiH tn iTiHiofitp tVisit £it Ipfi^t*
from a strict performance standpoint. It Is possible
to take advantage of the desirable properties of
methylene chloride without necessarily resulting
In a formulation that Is predominately based on
this material.

formulation number 23, a group of NMP formula-
tions stands out as the next best performance on
polyurethanes. While there are slight differences
In rank order, these same formulations also ap-
peared within the second  tier grouping  on the
other coatings. In general, the ether/ester for-
Comments and
It is important to remember that  the  data
presented were generated for laboratory screening
purposes only.  From a practical application

standpoint,  the experiment did not attempt  to
directly translate the time to atrip a teat panel
section to that required to actually atrip a piece of
lurnlture. Also, there la no direct Indicator of the
relative increase In difficulty associated with atrip-
ping coatings that have cured for yeara veraua a
Irw wceka; the teat only ahowa that even a relative-
ly short cure tlmr dors Indeed Increase the difficul-
ty. Attempting to .strip multiple layera of multiple
typea of coatings would add yet another degree of
complexity to the overall equation, Thua, while the
data air useful  In determining general  trenda In
performance, It would he erroneous to assume that
(he addition of practical end-use difficulties would
necessarily  result In a simple, proportional In-
crease In time. Laat,  no attempt watt made  to
assess arty potential differences in recoatabllty or
preparation time required to recoat,
    The laboratory  teat concentrated on aome of
the measurable aspects of performance. Aa men-
tioned previously, other conalderattona are equally
Important In defining the "ideal" paint  stripper,
Including safety and toxlcity, aa well aa coat, waate
dlapoaal, and other environmental aapecta.  It ia
widely accepted  that the methylene chloride for-
mulationa  currently In  use  were developed  in
response to the needa for  reduced flammability
and  performance on a wide variety  of coatings,
These  same formulations  are now  being
scrutinized because of concerna about toxlcity, To
develop better paint a trippers, all these considera-
tions must be evaluated in concert, including ap-
propriate attention to relative risk,  Conversely,
focusing on only one consideration will moat likely
result in almply trading one problem for another
at aome future time.

ACKNOWLEDGEMENT: The experiments and data
presented in this paper were generated  by R.  T,
Roblnette, III, and J. B. Cuclc, Dow Chemical Company,


       Substitute Solvent fii

     Non-solvent Alternatives
              Chain Sandra Eberlc
          Directorate for Program Management and Budget
           II,S. Consumer Product Safety Commission

              Chain Qlcnn Simpson
            Directorate for Economic Analysis
           U.S. Consumer Product Safety Commission

DBE-based Stripper Formulations
Harold L. Jackson
Du Pont Chemicals Experimental Station
Wilmington, Delaware

Du Pont dibasic esters are refined dimethyl esters
of adiplc, glutaric, and succlnlc acids. Dibasic
esters are manufactured from a mixed  acid
coproduct stream obtained from Du Font's three
adiplc acid plants. The primary refined ester
product Is designated DBE. Du Pont fractionates
DBE to provide other mixtures and pure com-
ponents to satisfy market demands (see Fig.  1).
BE n-4 17%
n-3 66%
n-2 17%
n-4, 24% n-4, 90% n»2. 99% n=3,99%
Figure 1.—Dibasic esters.

   The DBEs are stable, low-cost liquids with
high boiling and flash points and low toxlcity; they
possess excellent solvent properties.  DBE Itself
has become one  of the leading high-boiling
oxygenated solvents used In the paint industry.
   As Indicated by their solubility parameters,
DBE. DBE-2, and DBE-3 are similarly good sol-
vents for many of the resins used in paints and
other coatings (see Table 1). Because of their sol-
vency and excellent overall balance of properties,
the DBEs and their blends with other solvents are
being used to replace methylene chloride in several
areas, Including paint cleanup and paint strip-
Stripper Formulations

The DBEs can be used alone for stripping a num-
ber of paints; however, like methylene chloride and
N-methyl pyrrolidone (NMP),  they perform best
when formulated with other selected solvents. Du
Font's interest Is in selling the DBE solvents—not
in manufacturing paint  strippers. Development
and evaluation of paint stripper formulations were
undertaken to provide guidance to customers In-
terested in paint stripper manufacture. These for-
mulations have been presented to the Industry as
starting points that hopefully can be improved by
those in the paint stripping Industry.
    For stripping a wide  range of paints, a base
blend of 70 to 80 percent DBE and 20 to 30 percent
NMP is recommended (see Table 2). Experience
has shown such blends to be  more effective than
either solvent by itself. Further, such blends are
cost effective, since DBE (a relatively low-cost sol-
vent) Is the  principal component, while the high-
cost NMP is minimized. The preferred dibasic
esters in these blends are DBE-2 or DBE-3 be-
cause of their very low vapor pressure.
Table 1.—Dibasic esters properties.

Molecular weight (av.)
Distillation range, °C (°F)

Vapor pressure, 20°C (Torr)
Flash point, TCC, "F
Solubility in H8O, wt. %, 20°C
Solubility parameters (Hansen)
Hydrogen bonding




Table 2.—Paint strippers.
Du Pont DBE-2
Aromatic 1501
Conosol* C-2002
Potassium oleate (50% in H2O)
Methocel* 31 13
Flash point, TCC, °F
Cost (approximate), $/gal"
'Product of Exxon Chemical Co.
2Product of Conoco.
3Product of Dow Chemical Co.
'Materials costs based on "list" prices.
    These formulations were developed with the
objective that they would be used primarily In the
original equipment manufacturing (OEM) sector.
However, in addition to testing for OEM needs, the
formulations were tested on wood coatings to cover
a wide variety of paints and finishes. The excellent
performance on  the  wood  coatings generated
much Interest in DBE-based strippers  for wood


Stripping performance of DBE-based formulations
versus  methylene chloride-based  formulations
was measured on painted wood panels  prepared
according to lobst et al. 1983.  Eight paint types
(Table 3), including five pigmented and three clear
coatings,  were tested over #2  pine kiln-dried
boards (nominally 1" x 6" x 10'). Three coats were
applied with a one-day interval between coats. For
the pigmented paints, each coat  was tinted a
different color. After drying In air for five days, the
boards were dried at 120°F for  two weeks In a
ventilated oven. All  coated  panels were stored
under ambient conditions for at least 60  days
before use.

Table 3.—Paint and varnish  materials.
   The methylene chloride-based strippers used
were the following commercial products:

    • Formby's Paint Remover, Superior Wood
      Formula (Formby's, Inc., Olive Branch,
      MS 38654). According to the label, the
      stripper contains methylene chloride and
      methanol (<4 percent).

    • Zip-Strip* Paint-Varnish and Stain
      Remover (Star Bronze Co., Alliance, OH
      44601). According to the label. It contains
      methylene chloride, mineral spirits, and
      methanol (<4 percent).

Stripper Application and Removal

All stripper  application  and removal tests were
conducted at approximately 75°F.  The stripper
was applied In heavy coat using a brush. The area
covered by the coating was approximately 2.75" x
4.0" or 11.0 square inches.  For the DBE-based
strippers. 2 to 4 g of stripper were used to cover
the  11-square-Inch  area. For  the  methylene
chloride-based strippers, 5 to 7 g of stripper were
    The DBE-based strippers were  allowed  to
remain In contact with the painted surface for 30
minutes. At the end  of this time,  no losses  in
weight of the strippers were noted. The methylene
chloride strippers, each containing a wax to slow
evaporation, were allowed to contact the painted
surface for 20 minutes. At the end of this time, no
losses In weight of the strippers were noted.
    The stripper-treated  coatings were removed
with a putty knife having a 1.5" blade. Whereas
the methylene chloride-based strippers swelled
and lifted the coatings In a somewhat bubble-like
fashion,  the DBE-based  strippers generally sof-
tened the coating with minor lifting and bubble-
like action. The softening action of the DBE-based








Latex exterior enamel

Alkyd enamel exterior


Vinyl acrylic interior


Polyurethane varnish

Marine paint

Marine varnish









Top Coat(s): Muralo Latex High Gloss Enamel
Prime Coat: Bruning 1210 Undercoat
Top Coat(s): Bruning House & Trim
Prime Coat: Bruning 1210 Undercoat
Top Coat(s): Parks Gloss Lacquer
Prime Coat: same as top coat
Top Coat(s): Muralo SemiGloss Vinyl Acrylic Latex
Prime Coat: Bruning 1210 Undercoat
Top Coat(s): Bruning Chemical Resistant Modified
Epoxy Coating #688 White Base
Prime Coat: Bruning 1210 Undercoat
Top Coat(s): McCloskey Gloss Polyurethane
Prime Coat: same as top coat
Top Coat(s): Pettit Easypoxy High Gloss Marine Finish
Prime Coat: Pettit Specialty Fiberglass Undercoat
Top Coat(s): McCloskey Man-O-War Gloss Spar
Prime Coat: same as top coat

                                                                     Reducing Risk In Paint Stripping
coatings generally extended deep Into the coating.
allowing ready removal when scraped with the
putty knife or wiped with a cloth.

Stripper Evaluation

Following stripper application and removal, the
effectiveness of each stripper's performance on
each coating type was evaluated visually. Since, in
the case of the paints, each of the three coats was
tinted differently, the amount of each coat was
rather easily judged. For the clear coatings, it was
assumed that most unremoved coating was  from
the first coat that had been applied.
   Results of the evaluation are tabulated In
Table 4. Plate  I is a photo of the stripped test
panels. The results show that paint and varnish
removal by the DBE-based strippers is generally
as effective as with commercial methylene
chloride-based strippers. However, removal by the
DBE-based strippers is slower by a factor of 1.5.
Because of the very  low vapor pressure of the
ingredients of the DBE-based strippers, they can
be left on the paint for extended periods without
loss  of the  solvents, thereby providing more
flexibility in working time.
Waste  Management and Cost

The solvent components of the stripper formula-
tions  discussed can be recovered for reuse by
distillation under vacuum. Handling of the solid
wastes,  mainly paint components, depends on
their nature and composition. In industrial usage,
such as auto paint booth cleanup, solvent recovery
and reuse are feasible. For small stripping Jobs,
such as the household,  waste handling proce-
dures, like those recommended In the Klean-Strip
Guide to Paint  & Varnish Removal, should be
   As noted previously, materials' cost of the
DBE-based strippers described are in the range of
$5.50-6.00/gal. or $0.61-0.71/lb. Since 2 grams
of stripper will  strip 11 inches, the stripper
materials' cost is $0.04 for 1 square foot. Du Pont
has no data on other costs involved in the stripping
process  and therefore cannot make a  complete
cost estimate.
Handling and Safety

DBE dibasic esters are of low toxlclty and have
such a  low vapor pressure that airborne con-
centrations are extremely small. However, as with
all organic solvents, the DBEs should be handled
with good ventilation to minimize exposure.
    There have been reports of blurred vision as-
sociated with the use of paint strippers containing
DBE. In all cases, the effect was noted when the
DBE was misused, I.e., used with Inadequate ven-
tilation and violations of Du Font's recommended
exposure guidelines. There have been no reports
of blurred vision associated with the use of DBE-2
or DBE-3.
Table 4.—Stripper performance.

1 . Acrylic latex
Exterior enamel
Alkyd primer
2. Alkyd exterior enamel
Alkyd primer
3. Nitrocellulose lacquer
4. Vinyl acrylic interior
Alkyd primer
5. Epoxy
Alkyd primer
6. Polyurethane varnish
7. Epoxy marine paint
Specialty undercoat
8. Alkyd marine varnish

         Plate 1.—DBE solvent paint stripping results.
    Good practice also requires that, as with all
organic solvents,  skin contact should be  mini-
mized. Animal tests indicate DBE is a mild skin
irritant, but is not a skin sensitizer.
stripping action,  strippers containing a 75/25
mixture of DBE and N-methyl pyrrolidone remove
most paints and varnishes as effectively as com-
mercial methylene chloride-containing strippers.

Du Pont dibasic ester solvents, particularly DBE-2
and  DBE-3, can be formulated to effective paint
strippers having low toxicity, low VOC, and
moderate cost. Although slightly slower in their

J. lobst, D. Sellers, R.G. Flowers, and S. Ebbert. 1983.
    Paint Removers. Rodale Product Test. Rep., Product
    Test. Dep. Rodale Press, Emmaus, PA.
Guide to Paint & Varnish Removal. "Kkan-Strlp" Market-
    Ing Dept., P.O. Box 1879, Memphis TN 38101.

Surface  Tension Modification  of
NMP-based  Paint  Strippers
William C. Walsh
BASF Corporation
Parsippany, New Jersey

The solvents traditionally used In paint strippers
include methylene chloride, methanol,  acetone,
and methyl ethyl ketone. In evaluating stripping
speed, these products have some common proper-
ties that play a key role In their ability to remove
paint quickly (Table 1).

Table 1.—Solvent property data.

Methylene Cl
   • All of these solvents consist of small,
     non-complex molecules. This allows fast
     and efficient solvent penetration of the
     cured paint or coating.
   • They all have high vapor pressures
     resulting in fast evaporation rates. The
     quick evaporation of solvent aids in lifting
     paint from the substrate.
   • They also have low surface tensions. This
     allows them to quickly "wet out" all
     surfaces, fill any surface pores, and begin
     immediate penetration of the paint film.

   In combination, these  properties result in
paint stripping formulas that can remove most
common paints and coatings quickly and effective-
ly. N-methyl pyrrolidone (NMP), in comparison,
has relatively different properties of molecular size,
vapor pressure, and surface tension that result in
slower stripping times.
   • NMP is a larger molecule. As such, NMP
     simply requires more time to penetrate a
     given coating.

   • NMP has a lower vapor pressure. After
     penetration of the coating, highly volatile
     solvents will lift as they flash back
     through the paint film. The low volatility
     of NMP slows this lifting process.

   • NMP has a higher surface tension. The
     surface tension of NMP is nearly double
     that of other paint stripper solvents.

   If any of  these key  properties could be
modified,  perhaps the stripping speed of NMP
could be Improved as well. Molecular size is fixed,
and although vapor pressures and surface ten-
sions can be  reduced through increasing tempera-
ture, this is not a common practice in most paint
stripping applications. However,  through the ad-
dition of an  appropriate surfactant, the surface
tension of NMP blends can be modified to improve
stripping speed.
Product Description

Five NMP-based formulas were reviewed in this
study to determine their effectiveness as  paint
strippers. The compositions of these five blends
with their respective flash points are listed in Table
2. (Note: Flash points were determined by ASTM
method D-56, Tag Closed Cup.)
   For safety considerations, cosolvents were
chosen so that low volatility and high flash point
would be maintained In the final blend. As  re-
quired, cellulosic thickeners were added to  In-
crease viscosity.  Further  information on  the

Table 2.—Paint stripper formulas.

Hisol* 152
Dowanol* TPM5
Klucel* H-PR7
Flash Point
31 .0%











 'Footnotes 1-7 reter to product sources.

blending and use of these formulas Is available In
the BASF publication. "Formulating Paint Strip-
pers with N-methyl pyrrolldone."


All of these formulations demonstrated good paint
stripping ability  In  removing commonly used
paints and coatings. During testing, performance
data  were developed  on the ability  of  these
products  to  strip  acrylic  latex,  alkyd,
polyurethane. and epoxy coatings from wood sub-
    Use of NMP paint strippers Is similar to that of
any other stripper. The product is applied to the
substrate with a brush or roller and given suffi-
cient  time to penetrate the coating. A thickened
version will strip walls or ceilings.
    Following application, the residual stripper,
paint flakes, and dissolved pigment are  easily
removed with a standard plastic or metal scraper.
Since all of these products will slowly evaporate.
the following procedure Is recommended to ensure
complete removal of spent solvent from surfaces:

    • Step 1:  After the  stripper and paint have
      been scraped  from the surface, wipe the
      area clean with a cloth or absorbent towel.

    • Step 2:   Using a wet cloth or towel, dean
      any residual formula from the surface. As
      these products rinse well with water,  any
      residual solvent is easily removed.

    • Step 3:  Using a dry cloth or towel, remove
      any excess moisture and then allow the
      surface to air dry for several minutes.

For most projects, a single application of the strip-
per Is sufficient, even when stripping thick (multi-
ple) paint layers.

As  stated earlier,  one of the primary trade-offs is
stripping speed versus solvent Inhalation. One
method for judging the relative risk of Inhalation
Is to compare the ratios of equilibrium vapor con-
centration (EVC)  to permissible exposure limit
(PEL, eight-hour average) for each solvent. These
data are listed In Table 3.

Table 3.—Vapor concentration data (@ 20°C).	
                   EVC        PEL
                  (PPM)       (PPM)       RATIO
Methylene Cl
Hisol* 15
Dowanol* TPM
'Denotes producer's recommendation.
    Higher ratio values indicate relatively higher
risks of inhalation exposure. For Instance, NMP's
ratio of 3 versus methylene chloride's ratio of 900
Indicates that the risk of inhaling a concentration
of methylene chloride  above the recommended
PEL is 300 (900/3) times more likely than when
using NMP under the same conditions.
    In other words. NMP provides the user with a
greater margin of safety from Inhalation than the
more common paint stripper solvents.
    As with any solvent,  rubber gloves must be
used to prevent severe drying and potential blister-
Ing of exposed skin. If any skin comes Into contact
with an NMP blend, the exposed area should be
Immediately rinsed with  water. Also, customers
should use these products In well ventilated areas
and wear goggles throughout  the  stripping
    The NMP blends tested in this study have flash
points in the  range of 140° to 200"F. As such, all
of these compositions result in combustible, but
not flammable, mixtures.
 Product Performance

 NMP-based formulas will effectively strip the fol-
 lowing coatings:
    • Acrylic latex gloss enamel
    • Household epoxy spray paint
    • Polyurethane gloss enamel
    • High gloss polyurethane wood finish
    • Tallow oil alkyd spray paint

                                                                        Reducing Risk In Paint Stripping
   In this study, the listed coatings were stripped
from wood. These formulas also strip similar coat-
Ings from other substrates (metal, plastic, glass,
concrete) effectively.

Time Requirements

With sufficient time,  NMP blends can be quite
effective  paint strippers. In some cases,  these
blends required longer contact time than conven-
tional stripping formulations.
   In general, the longer working times were re-
quired when stripping higher, crosslinked coat-
ings.  For certain  blends,  lowering  the surface
tension resulted in noticeably faster stripping.
   To quantify the Impact that surface tension
has on stripping speed, the original five formulas
were  modified with a nonlonic surfactant,
Fluorad® FC-430. Shown in Table 4 are the
original formulas modified to contain 0.2 weight
percent of Fluorad® FC 430. Flash points of the
new mixtures are listed as well.

 Table 4.—Paint stripper formulas using Fluorad.'

Dowanol* TPM5
Klucel* H-PR6
Flash Point
31 .0%






1 .0%



1 .3%

1 .0%

 'Footnotes 1-7 refer to product sources.

    After addition of the surfactant, each modified
formula was compared to the original, unmodified
version. The results of these tests are shown in
Figure 1.
    Pure NMP   n     »2

            [22 Unmodified
            *3      »4

           Floored modified
NMP Pure
NMP+0.2% Fluorad*
Figure 1.—Surfactant-Induced surface tension reduction.

      To measure relative performance, tests were
   conducted to observe the time  required  to  lift
   various coatings from wood at room temperature.
   The modified NMP blends were tested against the
   original formulas, as well  as Zip-Strip, a common
   methylene chloride-based product. Table 5 lists
   the results of these tests.
      In actual use, those blends modified with
   Fluorad® demonstrated a noticeable improvement
   in  stripping speed  when removing urethane
   enamel and household epoxy, the more complex of
   the coatings tested. This  Increase in efficiency is
   illustrated by Figures 2 and 3.
Table 5.—Comparative stripping times (minutes).

Formula #1 :
+ 0.2% Fluorad
Formula #2:
+ 0.2% Fluorad
Formula #3:
+ 0.2% Fluorad
Formula #4:
+ 0.2% Fluorad
Formula #5:
+ 0.2% Fluorad
Methylene Chloride





























 'Footnote 8 refers to product source.

  Strip Tim* (mlnut**)
  Formula *1  Formula J>2 Formula #3  Formula *4 Formula *6

       £S3 Original Formula*  HI Modified Formula*

Figure 2.—Urethane stripping time Improvement.
  atrip Time (minute*)
  Formula »1 Formula »2 Formula 09  Formula »4 Formula

        E22 Original Formula  •• Modified Formula

Figure 3.—Epoxy stripping time Improvement.

    Even after reducing the time required to strip
urethane enamel and household epoxy, the NMP
formulas are slower than the methylene chloride
product. Again, the trade-off Is one of stripping
speed versus the possibility of solvent inhalation.
NMP works slower but contains less solvent vapor.
Waste Management

Material Recyclability

A significant amount of the spent stripper is poten-
tially reusable solvent. However, as this Is a thick-
ened mixture, conventional distillation techniques
of recovery are unrealistic and any paper waste
collected during use of the product further com-
pounds the problem.
    If a sufficient volume of thickened residue were
Isolated, a filter press could be used to separate
the spent solvent, which could then be distilled
and reused.
Waste Generation

All of the compounds used in these NMP-based
formulas have low vapor pressures. Until physical-
ly removed, a large amount of residue will remain
on the substrate for a long time (Fig. 4).
                                                     Sample Weight (grama)
    Formula #1 Formula 2  Formula #3 Formula 
                                                                         Reducing Risk In Paint Stripping
  Evaporation <*)
                 1      16      2
                Elapsed Time (hours)
Figure 6.—Evaporation loss Is minimal (short term).

   In those areas of the country where household
chemicals are sorted from other garbage, these
bags of residue should be separated for proper
Stripping Cost

Usage cost Is another factor when developing NMP
blends. Each of the five coatings examined in this
study was removed in a single application of an
NMP blend. The methylene chloride product, Zip-
Strip, also removed each coating In a single  ap-
    However, the volume of the NMP blend re-
quired for a single coat was approximately 38
percent less than that required to strip any given
surface area. NMP strippers may be more expen-
sive per gallon than traditional products. However,
less product Is required to achieve similar results.
(See Fig. 7.)
       Qilloni/Squtr* Foot
       NMP-b«»»d Formula*           Zip-Strip

Figure 7.—NMP blends are more efficient.
The search for alternative paint strippers will likely
include several alternative solvents. In comparison
to traditional paint strippers, the primary differen-
ces are Issues of stripping speed versus the pos-
sibility of solvent inhalation  and  product cost
versus usage cost.

   • NMP blends work slower than traditional
      paint strippers, but  NMP generates less
      vapor during the stripping operation than
      do  the more  common  paint stripper

   • NMP blends  may be more  expensive  per
      gallon, but they will cover more surface area
      per gallon  than will  traditional paint

   In evaluating replacements for traditional sol-
vents, these trade-offs must be carefully reviewed
before  selecting and  using an alternative paint
stripper. In some applications, stripping speeds of
NMP-based formulas can be Improved by lowering
the surface tensions of the blends.

Flick. E.W. 1985. Pages 469-73. 492-98 in Industrial
    Solvents Handbook, 3rd ed. Noyes Data Corp.
Monlck, J.A. Pages 70-72 In Alcohols, Their Chemistry,
    Properties, and Manufacture. Relnhold Book Corp.
Rlddick, J. A. 1986. Organic solvents: physical proper-
    ties and methods of purification. Pages 36-40 (n
    Techniques of Chemistry. 4th ed. Vol. n. Wlley-In-
    tersclence Publ. New York.
Weast, R.C. 1989. Pages F-88, D-274-80 In CRC Hand-
    book of Chemistry and Physics, 69th ed. CRC Press.
Product Information Brochure: Fluorad* Coatings Addi-
    tives FC-430, FC-431, 3M Industrial Chemical
    Products Division, Issued 11/89.
Product Sources
1. BASF Corporation, Porstppany. NJ.
2. Ashland Chemical Company, Columbus. OH.
3. Eastman Chemical Products, Inc.. Klngsport TN.
4. Dow Chemical Company, Midland, MI.
5. E.I. du Pont de Nemours & Company, Wilmington, DE.
6. Hercules, Inc., Wilmington, DE.
7. 3M Industrial Chemical Products Dlv.. St Paul, MN.
8. Star Bronze Company, Alliance, OH.
    Hlsol* is a registered trademark of Ashland Chemi-
cal Co. Dowanol* and Methocel* are registered
trademarks of Dow Chemical Co. Klucel* Is a registered
trademark of Hercules, Inc. Fluorad* Is a registered
trademark of 3M Corporation.

                        Appendix A: Sample Preparation

(3) Layers of Alkyd:

  A 2" x 8" x 10" piece of white pine board was sanded and then cleaned of all dust. The board was
then spray painted with three thick coats of alkyd spray paint with 24 hours drying time between each

  Coat 1: a green Tallow oil alkyd spray paint manufactured for Hardware Wholesalers, Inc. (HWI)
2012 green HWI No. 789-855, Lot #F033.

  Cnat 2; a brown Tallow oil alkyd spray paint manufactured for Hardware Wholesalers, Inc. (HWI)
2036 brown HWI No. 789-757, Lot #6174-2734.

  Coat 3: the same green described above.

  Reference:  BASF Laboratory notebook - August 27,1988.
(2) Layers of Household Epoxy:

  A 2" x 8" x 10" piece of pressure-treated wood was sanded and then cleaned of all dust. Two coats
of epoxy spray paint were applied to the surface. A drying time of 72 hours was allowed between
coats. Before application of the second coat, the first coat was lightly sanded and cleaned of all dust.

  Coat 1: NYBCO Epoxy Spray Paint Code #1901 Appliance Snow White, lot # CP-81, manufac-
tured by: New York Bronze Powder Co., Inc., Elizabeth, NJ.

  Coat2r NYBCO Epoxy Spray Paint Code #1912 Coffee Brown, lot # BC-72, manufactured by:
New York Bronze Powder Co., Inc., Elizabeth, NJ.

  Reference: BASF Laboratory notebook - September 19,1988.
(2) Layers of Acrylic Latex Enamel:

  A 2" x 6" x 8" piece of white pine board was sanded and then cleaned of all dust. The board was
then painted with two coats of acrylic latex gloss enamel. The paints were applied with a polyester
bristle brush. A 24 hour dry time was allowed between each application. Also, the surface of the first
coat was lightly sanded and cleaned before the second coat was applied.

  Coat 1: JET-DRI® Acrylic Latex Gloss Enamel Code #00, Gloss White lot #AEA10 13E048,
manufactured by: Desoto, Inc. Des Plaines, IL.

  Coat 2: JET-DRI® Acrylic Latex Gloss Enamel Code #33, Azure Blue, manufactured by: Desoto,
Inc., Des Plaines, IL.

  Reference: BASF Laboratory notebook - September 19,1988.

                                                                 Reducing Risk In Paint Stripping
(2) Layers of Urethane Enamel:
  A 2" x 6" x 8" piece of white pine board was sanded and then cleaned of all dust. The board was
then painted with two coats of urethane enamel. The paints were applied with a polyester bristle
brush. Coat # 1 was lightly sanded and cleaned of all dust prior to application of the second coat, 24
hours later.

  r.nat 1: JET-DRI® Polyurethane Gloss Enamel Code #17 Autumn Brown Lot #AE112 13048,
manufactured by: Desoto, Inc., Gainesville, TXL

  rnat 2: JET-DRI® Polyurethane Gloss Enamel Code #00 Gloss White Lot #AE 132 13E033,
manufactured by: Desoto, Inc., Gainesville, TX.

  Reference: BASF Laboratory notebook - September 19,1988.
(1) Layer of Urethane Wood Finish:

  A 2" x 6" x 24" piece of white pine board was sanded and then cleaned of all dust. The board was
then painted with polyurethane stain, which was covered with a urethane high gloss top coat. Both
stain and top coat were applied with a polyester bristle brush. Time between application of stain and
top coat was 24 hours. The stain coat was very lightly sanded and cleaned of dust prior to top coat

  Stain; High gloss polyurethane varnish stain Code # 61, Dark Oak Lot # 7568500612, manufac-
tured by: Red Devil Paints and Chemicals, an Insilco Company, Mt. Vernon, NY.

  Top Coat: High Gloss Polyurethane Code #70, Clear lot # 75685 00702, manufactured by: Red
Devil Paints and Chemicals, an Insilco Company, Mt. Vernon, NY.

  Reference: BASF Laboratory notebook - September 19,1988.
  JET-DRI  is a registered trademark of Desoto, Inc., Des Plaines, IL.

                    Appendix B:  Surface Coverage Comparison

Zip-Strip Sample

  A piece of finished oak board was measured and weighed. A coating of Zip-Strip was then applied
with a polyester bristle brush. The total surface of the wood was coated with the same thickness of
the stripper.  (All thin spots in the Zip-Strip layer were filled in.) A single application was required
to lift the finish that was on the surface of the oak substrate.  The resin system of the finish was not

  Measurement of board:  6" x 4" x 3/4"
  Weight of board alone: 227.5 Ig
  Weight of board + Zip Strip: 2S4.62g
  a. 6" x 4" = 24 in of surface coated with Zip-Strip
  b. 27.11c at 1.181 g/cc = 22.955 cc/24 in2
  c. 144 in  = 1 square foot = 137.73 cc

NMP Formula Sample

  A piece of finished oak cut from the same board described above was measured and weighed. A
coating of Formulation 4 (see Table 2) was applied with a polyester bristle brush. The total surface
of the wood was coated with the same thickness of stripper. A single application was required to lift
the finish away from the oak.

  Measurement of board:  9 5/16" x 4" x 3/4"
  Weight of board alone: 29137g
  Weight of board + Formulation 4: 31938

  a. 9 5/16 x 4" = 3725 square inches coated with Formulation 4
  b. 2821gat 1.0962g/cc = 25.73cc/3725in
  c. 144 in  = 1 square foot = 99.46 cc

  1000 cc = 1 liter  = 1.057 quarts

  NMP technology will cover 38.05 square ft/gallon (single application)

  1000cc/99.46cc = Xsqft/sqft
  X = 10.054 square ft /liter
  10.054 sq ft/X = 1.057 quarts/4 quarts
  X = 38.05 square ft/gallon

  Zip-Strip will cover 27.48 square ft/gallon (single application)

  1000cc/137.73cc =  X sq ft/sq ft
  X = 726 square ft/liter
  726 sq ft/X = 1.057 quarts/4 quarts
  X= 27.48 square ft/gallon

  A gallon of NMP formula will cover 38.46% more surface area than a gallon of Zip-Strip.


Woodfinisher's  Pride: An  Alternative  to
Current Chemical Paint Strippers
Steve Johnson
Creative Technologies Group, Inc.
Greenville, South Carolina
Current Technology and
Environmental Concerns

During the last five years, methylene chloride, the
active ingredient that has been used In chemical
paint strippers since the 1970s, has come under
increasing scrutiny for Its potential to damage
human health and the environment. Methylene
chloride has been shown to be an extremely toxic
chemical, and emissions and wastes resulting
from its use must be disposed of under EPA's
hazardous waste guidelines. Furthermore, it has
been linked  to the development of cancer In
animals, although its effect as a carcinogen on
humans has not been proven.
   Environment is becoming a consumer issue.
Effective products are no longer enough. Surveys
suggest that consumers will pay more for products
that do not pose health and environmental risks
(see Tables 1, 2, and 3 and Fig. 1 for results of
consumer surveys). These issues  have led
manufacturers to search for alternative methods
of stripping paint.
   Many of the products that have been formu-
lated to meet these needs have been marketed
without being thoroughly tested and evaluated.
Although some of these preparations do seem
safer, performance is markedly inferior to stand-
ard removers. In fact, it Is rare to find a product
that is both safe and effective, and in some cases,
alternatives contain chemicals that are equally as
hazardous as methylene chloride.
Percent   Aware
  70 r-




Source: National Tracking Study, 1990, Creative
      Technologies Group, Inc.

Figure 1.—Methylene chloride awareness (n=334),

Woodfinisher's Pride: A True

Woodfinisher's Pride is an alternative to methylene
chloride paint strippers that Is both safe and effec-
tive (see Tables 4 and 5 for summaries  of
Woodfinisher's Pride's performance and toxicity
attributes). Its qualities make It an excellent health
and environmental choice—It can be used indoors


(n = 334)
Median Age =
< $15M
< $25M
< $40M
< $50M
< S60M
< + $60M
No answer
Median income
ristics of survey respondents.
34 F
$36,800 °

Product Formulations Biodegradable
Product Formulations Mixture assumes the
Removed Coatings/ disposal status of
Finishes the particular coating
(EPA TCLP Procedure)
Product Packages Polyethylene + nylon
Reuse of Packages User receives $1.00
for each container
returned for reuse/
Source: Creative Technologies, Inc.
Igure 2.— ^Woodflnlsher's Prlda environmental attributes.
ompetitive price and created an effective market
tratfttv fnr tVi«» r»rnrtii/»t
 Source: National Tracking Study, 1990, Creative Technologies Group, Inc.
 Table 2.—Opinion of methylene chloride among aware
 Not environmentally safe
 Source: National Tracking Study, 1990, Creative Technologies Group, Inc.

with adequate ventilation, has low toxlcity, is non-
flammable and biodegradable, and cleans up with
soap and water. The active  Ingredient in  the
product, N-methyl pyrrolldone (NMP). has been
used Industrially for over 25 years, and thus has
over a quarter  century of  testing and usage to
substantiate claims (see Fig. 2).
    The product was not previously brought to the
consumer market because It Is relatively expensive
and early formulations performed poorly. Now, the
Creative Technologies Group, Inc., has success-
fully developed  a formula for consumer use at a
    Woodflnlsher's Pride Is a paint and varnish
stripping gel.  The product Is suitable for wood,
glass, and metal, and can remove lacquer, acrylic,
polyurethane, alkyd enamel, shellac, latex, var-
nish, and epoxy. Because traditional methylene
chloride strippers evaporate  twice as fast as
Woodflnlsher's Pride (and require "patchwork ap-
plications"). Woodflnlsher's Pride is actually 27
percent less  expensive to use than the other
products. In most cases, it removes multiple layers
of coatings in 30 minutes with no reapplication
(see Table 6  for a  cost comparison of Wood-
flnlsher's Pride with  traditional strippers). With a
rate of evaporation 360 times slower than methy-
lene chloride, the product stays wet for hours, thus
extending flexibility of use. It does not leave a waxy
residue, as do many strippers, and will not raise
wood grain or lift veneers because it does not
contain any water.
         Primary Ingredients

         Woodflnlsher's Pride for paint works by swelling
         the polymer bonding paint to the substrate, caus-
Table 3.—Unmet paint stripping consumer needs (n = 334).
                                       IDEAL PRODUCT
                CURRENT PRODUCT
                              (GREATEST PRODUCT
Safer around children
Biodegradable/environmentally safe
Easily removable from curves or comers
Source: National Tracking Study, 1990, Creative Technologies Group, Inc.
Key: 10 = Extremely Important
     1 = Not at All Important

                                                                                  Reducing Risk In Paint Stripping
Table 4.—Attributes of Woodfinlsher's Pride.


Stripping gels
Consumer paint and varnish

NMP + Activators
NMP/BLO + Activators

Replace Traditional Strippers
30 minutes or less
No special tools
Steel wool/metal scrapers
Eye/skin irritant
Flash point = 194F
Not flammable
No offensive fumes
One-step application
Soap and water cleanup
Personal safety
15-20% more expensive
  unit price (less expensive
  for total job)
Source: Creative Technologies Group, Inc.
ing the coat to break and lift from the surface. The
product for varnish breaks  the carbon-nltrogen-
oxygen/urethane bond, causing the  varnish  to
separate from the surface.

    Woodfinlsher's Pride contains three primary
Ingredients:  NMP  (N-methyl  pyrrolldone) Is a
water-soluble, biodegradable  solvent;  it has low
toxlcity,  Is  nonflammable and noncarclnogenlc,
and has been approved by EPA for  preharvest
usage (see Table 7 for N-methyl pyrrolidone test
results).  Gamma-Butyrolactone, a second  active
ingredient,  is also water  soluble and bio-
degradable, and has been cleared by the Food and
Drug Administration for use in multipurpose food
flavorings as defined by the Food Extract Manufac-
turers Association. The International Agency for
Research on Cancer concluded that Gamma-
Butyrolactone is noncarcinogenlc in rats and mice.
The third ingredient, Bitrex, is a nontoxic bittering
agent designed to prevent accidental Ingestlon by
 Table 5.—Woodfinlsher's Pride paint and varnish formulas' Irritation and toxiclty test results.

 TESTS                                                      FORMULA
 Acute oral toxicity:
   (LD-50 TEST)
 Primary skin irritation test
   (applied to abraded and intact sites, then
   occluded and examined)
 Primary eye irritation test
   (average ocular irritation scores)
   UNWASHED EYES:  1 hour
                     4 days
                    14 days
                              1.5-5.0 g/kg

                              Pll = 1.29
                              (slightly irritating)
                              (severe irritant)
                                    5.11 g/kg

                                    Pll = 1.54
                                    (mildly irritating)
                                    (extremely irritating)
 Source: Creative Technologies Group, Inc.
Table 6.—Cost-per-use comparison of Woodfinlsher's Pride vs. traditional strippers.
Average Retail Price: 32 ounces
Per ounce
Ounces Required per Square Foot
Cost per Square Foot
Total Difference


+ 42%
+ 42%
Source: Creative Technologies Group, Inc.
Note: Calculations based on the following lab data:
   Ounces required determined by ability to remove three coats of paint or varnish to bare wood, and considers any reapplication required due to evaporation
   of product from surface.
   Actual data:
   Methylene Chloride Products:
    Cost per ounce
    Ounces needed per square foot
   Cost per Square Foot

   Woodfinisner's Pride:
    Cost per ounce
    Ounces needed per square foot
   Cost per Square Foot






Table 7.—Af-methyl pyrrolidone, (primary Ingredient in Woodfinisher's Pride) Irritation and toxlclty tests results.
TESTS                                                                          RESULTS
Acute oral toxicity
(LD-50 on a variety of species)
Subacute feeding studies
(Wistar rats, Charles River mice, beagle dogs, game birds)
Skin irritation/chronic dermal toxicity
(rabbits, humans, guinea pigs)
Ocular toxicity
Inhalation hazard testing
(cats, rabbits, guinea pigs, rats, mice)
Injection toxicity
Carcinogenicity/mutagenicity studies
(Ames Test, Mouse Lymphoma Assay, CHO Forward Mutation Assay,
Unscheduled DNA Synthesis Assay)
(2-year inhalation study)
Embryotoxicity/teratology studies
Toxicity to aqueous organisms
Regulatory approval
   EPA preharvest approval
   EPA postharvest approval
   FDA slimicides-indirect food additive
          Low order of toxicity

          Low order of toxicity

          Skin irritant

          Eye irritant
          No effect
          (even at saturation)

          No activity
          Not teratogenic/embryotoxic at high levels (1 g/kg)
          Rapidly excreted
          Highly biodegradable
          Jan. 1985 (40 CFR 180-1001 (D) Pending
          Approved (21 CFR 176.300) GRAS
 Source: Creative Technologies Group, Inc.
Comparison with Other

Methylene Chloride Strippers
Woodflnisher's Pride does not contain methylene
chloride or other flammable or toxic chemicals; as
a result, the fumes are not dangerous when in-
haled, and it does not require extreme ventilation.
Also. Woodfinisher's Pride  does  not evaporate
quickly, so pieces do not have to  be stripped in
sections (see Figs. 3, 4, and 5 for  comparison of
Woodfinisher's  Pride with traditional methylene
chloride strippers).

Nonmethylene Chloride Strippers
With the exception of products containing dibasic
esters,  strippers presently being used as a sub-
stitute  for methylene chloride  products contain
other harmful and flammable ingredients such as
methanol, toluene,  and  acetone.   Dibasic  ester
products such as 3M's Safest Stripper are difficult
to apply, require several hours for  the product to
work,  and contain a high percentage of water,
which is damaging to wood substrates.
  % Weight Loss
  of Formulation





10 Minutes   20 Minutes  30 Minutes
 Source: Creative Technologies Group, Inc.
 Key:   0 Woodfinisher's Pride
        EM3 Traditional Strippers

Figure 3.—Formulation volatility comparison of
Woodfinisher's Pride vs. traditional atrippera.

                                                                                       Reducing Risk In Paint Stripping
 of Coats  Glidden  Red Devil Rickel's Pittsburgh Glidden  Rickel's Modern  Muralo   Muralo McCloskey Red Devil  Sears
      f  Acrylic   Acrylic   Latex    Latex   Exterior  Acrylic   Deck   Acrylic   Vinyl-   Polyure   Polyure   Latex
           Latex    Enamel  Exterior           Latex    Latex   Enamel  Enamel   Acrylic  Varnjsh   Enamel  Enamel








 Source: Creative Technologies Group, Inc.

 Key:    LMJ Traditional methytene chloride strippers
 Woodfinisher's Pride
 Figure 4.—Performance of Woodfinisher's Pride vs. tradtlonal methylene chloride strippers after elapsed time of 15
 of Coats Glidden Red Devil Rickel's Pittsburgh Glidden  Rickel's Modern  Muralo  Muralo McCloskey Red Devil  Sears
       -  Acrylic   Acrylic   Latex    Latex  Exterior  Acrylic   Deck   Acrylic   Vinyl-   Polyure   Polyure   Latex
           Latex   Enamel  Exterior            Latex    Latex  Enamel  Enamel  Acrylic  Varnish   Enamel  Enamel








 Source: Creative Technologies Group, Inc.

 Key:   t£j  Traditional methylene chloride strippers
Woodfinisher's Pride
Figure 5.—Performance of Woodfinisher's Pride vs. traditional methylene chloride strippers after elapsed time of 30

                                                              being debated, Woodflnisher's  Pride Is an
                                                         alternative that can provide excellent results and

Woodflnlsher's Pride  is  a  high-performance     generate good profits for retailers. Tables 8 and 9
product that is safer for the environment and the     compare response to Woodnnlsher's Pride and a

user than methylene chloride preparations. While     leadlnS methVlene chlorlde br^d.
the health consequences of methylene chloride are

Table 8.—Consumer study of Woodfinisher's Pride vs. Formby's/Strypeeze for stripping surfaces (N = 55, side-
by-side use).	
                                                         WOODFINISHER'S                           METHYLENE
Able to coat entire surface                                        7.73 *                                  6.50
Able to use inside                                               8.94 *                                  6.27
Biodegradable/safer to use                                        8.80 *                                  4.68
Able to clean up with water                                        8.50 *                                  5.57
Right consistency for vertical surfaces                               8.48 *                                  5.64
Able to reuse applicator brush                                     8.42 *                                  5.73
Easy to use                                                    8.24 *                                  6.47
Having a pleasant scent                                          8.06 '                                  4.91
Easy removal from surfaces                                       7.80 *                                  6.22
Safer around children                                            7.35 *                                  4.70
Easy removal from curves/corners                                  7.07 *                                  5.29
Easy removal of several layers                                    6.89 *                                  5.22

Overall Attribute Evaluation:                                       7.73 *                                  6.50
Overall Preference:	71% *	27%
Source: Consumer Usage Study, Creative Technologies Group, Inc.
Note: Paints tested were enamel, polyurethane, alkyd, latex, and acrylic.
• = Statistically significant at the 95% confidence level.
Key: 10 = Most satisfied
      1 = Least satisfied
Table 9.—Consumer Study of Woodfinisher's Pride vs. Formby's/Strypeeze for stripping varnished surfaces (N
= 157, side-by-side use).	^	

                                                          % PREFERRING                         % PREFERRING
                                                         WOODFINISHER'S                         METHYLENE
Biodegradable/safer for environment
Able to clean tools with soap/water
Easy to clean up
Having a pleasant scent
Able to use inside
Right consistency for vertical
Able to coat entire surface at once
Easy to use
Safer around children
A good value for the money
Removing coatings easily
Taking less time to do project
Able to remove several layers of varnish
Overall Preference
Source: Consumer Usage Study. MARKETING SPECTRUM.
Note: Varnishes tested were polyurethane and shellac.



Bix  Stripper:  An  Alternative to
Methylene Chloride
Gerald L Bixenman
Bix Manufacturing Company
Ashland City, Tennessee
       The risfcs/rom using paint strippers contain-
       ing methylene chloride are among the
       highest ever calculated/or chemicals Jrom
consumer products.
   This statement from  a 1985 Consumer
Products Safety Commission news release was
widely quoted in  the media and  discussed  on
celebrity and talk shows.
   The claim that there was no viable alternative
to methylene chloride was  stated  or implied in
virtually all of these accounts, but no source was
ever mentioned.
   There is, however, a viable alternative that has
been sold successfully for almost  30 years: Bix
Stripper, a stripper that has never contained
methylene chloride.
   While Bix Stripper will not remove epoxy, the
coating most frequently encountered by retail cus-
tomers Is cellulose lacquer.
   In fact, Bix  Stripper Is far superior to
methylene chloride formulations as a stripper of
lacquer, polyurethane,  varnish,  and shellac.
Epoxy-type coatings are seldom encountered on
furniture, cabinets, woodwork, and pianos that
retail consumers work on; they are usually found
In Industrial and business situations.
   Bix Stripper "melts" paint and finishes rather
that "blisters" them. The air that gets under the
blisters causes methylene chloride removers to dry
out quickly. In contrast,  when  the coating is
"melted" air cannot get under It, so It remains wet
and keeps working much longer.
   Most methylene chloride  strippers are
designed to remove the top coat. Repeat applica-
tions to remove multiple coats require more work
and much more remover. Bix Stripper's melting
feature enables the consumer to remove the bot-
tom coat first, thus requiring less work and much
less stripper.
   Bix Stripper is used extensively in interior
restoration. Its slow evaporation cuts vapor emis-
sions to a minimum, while removing the bottom
coat first saves a great deal of labor and material.
Bix stripper Is sold  in over 75 percent of home
centers, all hardware cooperatives, most hardware
and paint sundry distributors, and hundreds of
paint stores. It outsells methylene chloride for-
mulations in most areas. There is a viable alterna-

Substitute Chemical  Formulations  for
Professional  Furniture  Refinishing
David L. White
Kwick Kleen Industrial Solvents Inc.
Vincennes, Indiana
        Rrick Kleen Industrial Solvents manufac-
        ures industrial paint removers for the
        ommercial trades. According to a recent
CONSAD report contracted for by the Occupation-
al Health and Safety Administration, Kwick Kleen
products consume 7 percent of  the methylene
chloride used in this industry.  Kwick Kleen's
products are sold throughout the United States
and Western Europe for use in furniture reflnish-
ing and restoration, original equipment manufac-
turer recycling  of rejected parts, and general
recycling or manufacturing of durable goods.
   Kwick Kleen manufactures removers in six
chemical groups: non-flammable  methylene
chloride, petroleum base and oxygenates (with less
than 20 percent methylene chloride),  non-
methylene chloride proprietary,  N-methyl pyr-
rolldone, aqueous, and caustics.
   Kwick Kleen has experimented with the follow-
ing chemicals, which are being promoted as pos-
sible substitutes for methylene chloride:

   • Alkyl acetates

   • Dlacetone alcohols

   • Dibasic esters

   • Furfuryl alcohols
   • Monochlorobenzene

   • Monochlorotoluenes

   • Monoethanolamlne

   • Methyl amyl ketone

   • Af-methyl pyrrolldone

   • Propylene glycol monomethyl ether

   • Acetate trioxane

   Only N-methyl pyrrolldone and a combination
of two of the above sold as a non-methylene
chloride proprietary blend by Kwick Kleen show
any promise for use in the furniture trades.
   Because of the characteristics of wood and the
many finish treatments, paints, and combinations
of both that may have been applied to an item,
paint removal from the substrate poses unique
problems. There are 13 different types of groups of
clear finishes and over 30 different finishes. Add
paints, and there are thousands of combinations
that could be on the surface of the furniture.
   A marketable remover must meet 25 paint
remover characteristics before It can be Introduced
as a Kwick Kleen product. Recent tests were per-
formed on four types of finish coatings: stained

                                                                      Reducing Risk In Paint Stripping
and varnished, stained and lacquered,  multiple
coats of enamel paints over clear varnish, and
acrylic paint over stain and varnish. The first three
Items were chairs and the fourth a measured area
on a flat surface.
   Tests used the flow-over method. The time
stripped In minutes, percent of coating removed,
percent of stain removed, color to substrate (wood),
and percent of chemical bleed-out after stripping
are shown in the following table:
Methylene chloride
% coating
% stain
Color substrate
% bleed out
% coating
% stain
Color substrate
% bleed out
W-methyl pyrrolidone
% coating
% stain
Color substrate
% bleed out
Dibasic esters (DBE)
% coating
% stain
Color substrate
% bleed out
& & 3 COATS 1 COAT




    Labor varied from one re-coat for methylene
chloride  to 28 re-coats for the DBE remover.
Scrubbing was limited to no more than three tries
to allow the remover to do Its work. When com-
pared to the methylene chloride blend during this
test, the proprietary blend required 17 percent
more time, the NMP 20 percent more, and the DBE
took four times as long.
    Each of the substitutes Is more labor-intense
and costs  considerably more than methylene
chloride removers. The current prices per gallon in
55-gallon drums of the removers tested are as
follows: methylene chloride blend.  $4.95:
proprietary blend, $8.00:  N-methyl pyrrolidone
blend, $12.09;  and the  dibasic ester blend.
$17.95. The amount of remover used was 2,874
mil of the methylene chloride blend. 2,164 mil of
the proprietary blend. 1.710 mil of the N-methyl
pyrrolidone, and 2,043 mil of the dibasic ester.
Sludge from  the methylene chloride blend was
air-dried to a hard  solid  for land-fill disposal;
sludges from the other blends required hazardous
disposal because they were wet and flammable.
    It Is extremely Important to dispose of sludge
properly  because both the remover and paint
sludge pose threats  to human  health  and the
environment. Depending upon the thickness of
paint sludge, methylene chloride can evaporate
within hours,  leaving dried paint  and trace
residues of solvents. Thickeners will  also be
present if the formula was a semi-paste.
    Because of the low volatility of solvents found
In N-methyl pyrrolidone,  DBE,  and most other
substitutes, drying time extends Into days. Paint
sludge removed from an 80-square-inch test panel
at the Kwlck Kleen laboratory remained wet for
over 60 hours; inspection of the  sludge disclosed
continued solvent activity.
    Kwick Kleen has determined that sludge dis-
posed of while wet into a land fill poses an environ-
mental threat because  it  includes solubillzed
heavy metals, such as lead. EPA must consider the
environmental Impact of millions of gallons of wet
paint sludge as compared to that  of dried paint
chips of methylene chloride-based paint removers.
    To  rebutt a negative  statement about the
Flowover*system, repeated tests  have shown that
wood soaked in a paint remover absorbs  up to 80
to 90 percent more solvent than  wood exposed to
paint remover that has been applied by brush or
Flowover*pump. With a pump  system,  Interior
areas of desks and chests of drawers, undersides
of tables, or unfinished, unexposed areas of Items
are wetted  once with remover to prevent stains
from runs. The finish Is then scrubbed away with
the remover, which is applied through the brush
and directed only to the surface where needed. In
a soak tank,  all areas of the item, Including the
unfinished  Inside, are exposed to and absorb the
chemicals while the  remover is working on the
finished surfaces.
    Furniture can be stripped 20  to 30 percent
faster with a Flowover*brush than in a soak tank
because of  the brush's abraslveness and the cut-
ting action of  the remover flowing through it.
Moreover, proper ventilation Is easily  achieved
with a Flowover*system because  fumes can be
drawn from around  and  underneath the work
table. Research done by the National Institute for
Occupational Safety and Health  indicates that 85
percent  of the Industry  uses  a pumped flow
method to apply remover.
    Lastly,  the only equipment-related fatalities in
this industry have occurred when workers fall into
tanks or are overcome by chemicals when leaning
into tanks. In the Flowover*system, remover Is
pumped Into a tray at an optimal working height.


thereby eliminating the need for employees to lean
down into the tank.

Methylene chloride is the only suitable paint and
coating remover that is non-flammable. This Is of
considerable concern to most users since many
coatings  are  lacquers containing nitrocellulose
that, when mixed with a flammable remover, be-
come a substance similar to napalm.
    Because workers must be close to the work
and normally have the remover on gloves, apron,
and boots while working, a fire often results in
death. The National Fire Protection Association
data on fires in furniture repair shops from 1984
to 1988 show an average of one death and three
injuries each year. A death for each  100 fires Is
very high when compared to other business fires.
    With the Industry currently using only 5 per-
cent flammable paint removers.  It would be a
conservative estimate to increase the number of
deaths In proportion with the use. If the industry
converted to 100 percent flammable removers, the
number of deaths could rise to 15 and injuries to
45 per year. However, these figures do not take into
account the increase In hours that would result
from the slow cutting speed of the substitute paint

An  Alternative to  Methylene Chloride for
Removal of Lead-based  Paint
Stephen C. Arndt
Arndt Brothers Industries
Milford, Connecticut
        Housing authorities and environmen-
        talists nationwide are demanding the
        removal of lead-based paints from dwell-
ings and other structures in response to the in-
creased recognition of lead poisoning hazards. The
ingestion of lead in the form of paint chlpsand dust
can cause neurological damage, especially in
children and fetuses. In recognition of this hazard,
lead-based paints  have been  banned since the
1970s, but the problem of removing such paint
from older homes,  public buildings, and steel in-
dustrial structures, such as water tanks, remains.
   Until recently,  the paint removers used most
widely contained blends using methylene chloride,
a substance that In itself  poses substantial en-
vironmental and health risks. These substances
required multiple applications and are not suitable
for lead-based paint  removal because  of these
hazards and the problems created for disposing of
the resultant mixed hazardous waste.
An Alternative Method of
Paint Removal

A new form of caustic paint removers has proven
more effective and much safer, providing a "mini-
mum of chemical with the maximum effect." In the
late 1980s, a method called the Peel Away Paint
Removal  System was developed by Dumond
Chemicals, Inc., and has gained wide acceptance
among housing authorities and other groups chal-
lenged with large-scale paint (especially lead-
based) removal projects.
    The chemical  compound In Peel Away I is a
thick alkaline paste that is spread or sprayed over
lead-based paint. The paste is then covered with a
laminated cloth provided by the manufacturer,
which controls evaporation. The cloth Is  left on
until all the paint has emulsified; when removed,
the paste and paint adheres to it, and the stripped
surface is washed clean and neutralized.
   Designed for the one application removal of
multiple layers of paint from wood, brick, plaster,
metal, concrete, stucco, cast Iron, marble,  or
fiberglass, the system offers the advantages of safe
and effective lead-based paint removal and con-
tainment. First, the paint Is kept damp throughout
the removal process, assuring that lead-based
paint particles will not be dispersed throughout
the atmosphere in the area being stripped. The
paste, paint, and cloth are then removed Intact,
allowing for easy disposal. The paste contains no
toxic fumes or flammable solvents.
    Peel Away  ST-1 is also effective on multiple
layers of lead-based paint on steel structures; It
adheres to all Irregular surfaces and forms a self-
sealed environment in  about one hour. The
alkalinity of the product protects stripped steel
from corrosion. Peel Away contains a low percent-
age of caustic  chemicals—about 7 to 8 percent.
The paste form provides the ability to build thick-
nesses in proportion to the number of layers of
paint being  removed, ensuring a one-application
process. The paste form eliminates  danger from
chemical splash, and there is no chemical runoff
from unnecessary repeated applications. It also
clings to overhangs and verticals, making the ap-
plication process easier and safer.
 Procedures and Cost

 Proper set-up and procedure require dressing in a
 PVC suit, rubber gloves (taped to sleeve), a half face
 mask respirator (when removing  lead-based
 paints), and eye protection. The system allows for
 potential hazardous materials to be kept separate,
 i.e., liquid from solid waste. Other considerations

include the potential for heat exhaustion among
workers, especially those wearing chemical suits.
and the availability of clean water for emergency
use. A recent test on a four-bedroom apartment
where  lead-based  paint was being removed by
several methods showed no detectable exposure to
lead by workers using the Peel Away method.
   The process provides cost  control as well.
Since there is only one application, bids can be
accurately assessed and compared. It is also pos-
sible to estimate the total material cost and the
amount of by-products that will need disposal. The
solid waste generated is roughly equal to that of
material used (number of gallons of caustic paste
remover). The loss of water from  evaporation is
compensated by the absorption of liquified paint
and the fibrous laminated covering.
   The liquid waste from  the cleaning process
varies  from job  to job and from contractor  to
contractor; specialized vacuum equipment will
minimize the amount of water needed. High pres-
sure is not necessary and not recommended. The
procedure works best with a light spray and soft
scrub brush.
   As part of the Peel Away paste, there is a
natural buffer to bind the lead, severely reducing
the extent and rate in which these toxic metals
could one day re-enter the environment. As the old
paint is emulsified and enters a liquid phase, this
allows for an exchange of ions between the lead
and the buffers, forming a  new compound, lead
hydroxide.  In most instances, these buffers will
reduce the hazard classification as measured by
the TCLP. most likely to either a special waste or
even a non-hazardous level.
   Peel Away is also especially effective for histori-
cal renovation projects, since it can penetrate deep
grooves and crevices in decorative work. Approval
should be sought from local historical commis-
sions before beginning any such project.
   Caustic paste paint removers are not suitable
for hardwoods, veneer of plywood, aluminum, and
some decorative plasters; they also have difficulty
with  epoxy  coatings, urethanes, baked-on
finishes, and latex-on-concrete. To minimize risks
associated with a caustic paste remover, do a test
patch on different substrates. The test will verify
that the surface is suitable for the caustic paste
removal process and will determine the level of
corroslvlty of solid and liquid wastes and the best
method to treat or dispose of them. It will allow the
user to determine the optimal thickness and time
frame for the process. It will also allow testing for
the best method for cleanup and subsequent coat-
Ings or refinishing.
Projects Completed with
Peel Away

A number of large-scale paint removal projects
have recently been completed using the Peel Away
method. In 1988,  the Chattanooga Housing
Authority, Chattanooga, Tennessee, began remov-
ing lead-based paint  from more than  700,000
square feet In housing units throughout the city.
The  surface was 97 percent plaster. 2 percent
wood baseboards, and 1 percent metal door cases
and  headers.  The  best all-around surfaces  for
stripping and  containment with Peel Away were
metal  and plaster. Apartment units averaged
2,400  square  feet, and six people  were able to
complete 7,200 square feet (approximately three
units)  per day. The project cost was $2.75 per
square foot stripped.
   Texas A&M University at College Station used
the Peel Away process to strip 16 four-story ROTC
dorms. The surfaces were primarily rough porous
plaster with a heavy latex coating and a nonlead
paint abatement. Peel Away was applied  with a
Graco ram pump on 55-gallon drums with a 150-
foot hose. With one person spraying and three or
four persons applying the blanket, the average
coverage was 10,000 square feet per day. Because
of the roughness of the plaster, the larger portion
of the  crew was used for the final cleanup and
rinsing of the walls.
    Many historic renovation projects were also
completed successfully using Peel Away to strip
lead-based paint. One example, the First Church
of Christ. Milford, Connecticut, was built in 1839.
Its surface wood totals 19,500 square feet, and the
steeple Is 150 feet high. In one application, Peel
Away successfully removed more than 20 layers of
old lead-based paint.  The contractor set cost at
$6.15 per square foot (total cost $120,000), which
Included  total removal of lead-based  paint,
removal of lead-lined hazardous waste, surface
preparation, all necessary caulking and reglazlng,
one coat of oil primer, and two top coats of oil paint.
The  approximate cost  for hazardous waste dis-
posal was $20,000.
    Clearly,  the new approaches to caustic
removal of lead-based paint are economically vi-
able, effective, and safe. Peel Away, a process
developed by Dumond Chemicals. Inc., has been
shown to be especially promising and effective In
a variety of applications.
    This presentation focused on Peel Away I and
ST-1.  However,  Dumond Chemicals makes a
multifaceted range of removal products that strip
coatings from all types of surfaces.

        Exposure Control &
        Pollution Prevention
              Chair: Sandra Eberle
          Directorate for Program Management and Budget
           U.S. Consumer Product Safety Commission

              Chair: Glenn Simpson
            Directorate for Economic Analysis
           U.S. Consumer Product Safety Commission

Case Study: Control  of  Methylene
Chloride  Exposures During  Commercial
Furniture  Stripping
Cheryl L. Fairfield
Amy A. Beasley
National Institute for Occupational Safety and Health
Cincinnati, Ohio
      The furniture stripping Industry Includes
      an estimated 20,000 workers  who are
      employed by approximately 6,200 small
businesses, averaging three employees each. Fur-
niture strippers, In general, do not have an oc-
cupational safety and health program as an
Integral part of their business. Therefore, these
small businesses are unlikely to develop innova-
tive controls to protect their workers.
   At the National Institute for Occupational
Safety and Health (NIOSH), researchers  have
documented time-weighted average exposures to
methylene chloride In the furniture stripping In-
dustry ranging from 12 parts per million (ppm) to
over 2,000 ppm. The Institute recommends that
methylene chloride be regarded as a potential
occupational carcinogen and that methylene
chloride be controlled to the lowest feasible limit.
Researchers from the Engineering Control Tech-
nology Branch of NIOSH are therefore conducting
field research to develop, document, and evaluate
effective controls for methylene chloride In furni-
ture stripping facilities.
   NIOSH researchers implemented a control at
one facility on a retrofit basis. Workers who
stripped furniture in this facility using the existing
ventilation system had exposures to methylene
chloride of 600 to 1.150 ppm. NIOSH researchers
designed, installed, and evaluated a new ventila-
tion system (Flg.l), which Incorporated these
primary improvements:

   • A new local ventilation hood,

   • An increased amount of makeup air to the
     stripping area,
   • Removal of a panel of charcoal filters that
     caused a pressure drop, thus hindering
     the effectiveness of the ventilation, and

   • Improved work practices.
Figure 1.—New ventilation hood Including a slot hood and
a downdraft hood.
   The new ventilation system was tested over
three days with charcoal sorbent sampling tubes
for methylene chloride. The sampling results Indi-
cated that the new ventilation system lowered
exposures from 600 to 1,150 ppm to a geometric
mean of 25 ppm, with lower and upper confidence
intervals of 11 and 58 ppm, respectively (Fig. 2).
Conclusions and recommendations at the end of
the case study include the following:


    M»CI Concentration (ppm)
     Got 80  Nov 80  Jan 90  M«r(1)90  M«r(2)90  M«r(3)90
                     Oil* of !••(

Figure 2.—Methylene chloride exposures for old and new
control designs.
    • This facility should use the installed local
      ventilation as a combined hood,

    • Elimination of crossdrafts Is an important
      factor in improved control, and

    • Further reductions can be achieved by
      installing ventilation controls In the rinse

    Several other surveys have been conducted of
ventilation controls for methylene chloride in fur-
niture stripping, and reports from these surveys
are being prepared. In  one study,  a ventilation
system was designed at the same time that a new
stripping tank was Installed. The additional design
flexibility allowed for control to similar levels as
this other case study but  with considerably less
exhaust air. A final report will be completed In late

An  Investigation of the Reduction  of
Methylene Chloride  Volatility in Paint
Eric L. Mainz
Vulcan Chemicals
Wichita, Kansas

In 1986, Vulcan Chemicals and Occidental Chemi-
cal initiated a research project at the University of
Missouri-Rolla to identify  additives that would
reduce the evaporation rate of methylene chloride
In paint remover formulations.
   Research since 1988 has focused on develop-
ing a basic understanding of the evaporative
process in  these mixtures. To achieve this, an
experimental matrix was created in which a model
formulation was built up step by step. Common
elements of commercial stripper formulations—
methylene chloride, wax. thickening agent,
methanol, and toluene—were added in successive
matrix levels. At each level, additives that could
reduce the evaporation of methylene chloride were
Included In comparative studies.
   Researchers knew surfactants  provided
evaporation  barriers in volatile organic liquids.
Barrier enhancement was thought to be mainly a
question of desolubillzing wax in a critical area of
the solution near the surface. However, experi-
ments with surfactants In complex stripper for-
mulations did not show barrier enhancement.
Relatively small polar molecules such as N-methyl
pyrrolldone. Y-butyrolactone, and propylene car-
bonate showed some promise in preliminary tests
using simples solutions of methylene chloride,
wax, and other components.
   In another approach, researchers tested
glycerine as an additive because Its mutual immls-
ciblllty with methylene chloride suggests It can
form a liquid barrier film that could complement
the wax barrier. Experimental results In more
complex model formulations seem to have con-
firmed this concept. However, the effectiveness of
glycerine and the other additives depends on the
balance of polar and nonpolar solvents. In limited
testing, glycerine demonstrated barrier enhance-
ment in some commercial formulations.
   Both thermodynamic (equilibrium) and kinetic
(dynamic) effects were considered. However, while
lowering the equilibrium vapor pressure (i.e., the
thermodynamic activity) can appreciably lower the
evaporation rate, any drastic lowering will also
affect methylene chloride's ability to penetrate and
attack a coating. Therefore, the greatest chance of
success appeared to lie with a study of the kinetics
of evaporation.
   Evaporation rates are usually controlled by
creating a physical barrier between a liquid and
the vapor space above. Incorporation of wax Into
the formulations is the most common way to form
a barrier in commercial paint stripping products.
Some previous studies on solid films, including
waxes, have suggested that their brlttleness could
lead to erratic effectiveness. By contrast, a liquid
form could  be "self healing." The  researchers'
preliminary conclusion was that a combined liq-
uid-solid film might provide the optimum barrier.
Experimental Procedures

Sample Preparation
The desired quantity of wax was weighed Into a
tared bottle and the  approximate  amount of
methylene chloride added to obtain the targeted
wax concentration. This mixture was warmed In
hot water, often bringing methylene chloride to a
boil (in a fume hood) until the wax dissolved. The
bottle was dried, its contents rewelghed, and suf-

flclent methylene chloride added to achieve the
desired wax concentration.
    If appropriate, a thickening agent was weighed
into a 20  mL  screwcap bottle and methylene
chloride-wax solution added until solution volume
totaled  15 mL.  The solution was shaken and
reweighed before adding other components or ad-
    All samples were allowed to stand overnight
before evaporation rates were measured. By the
next day, the samples had usually gelled and, in
many cases, some of the wax had formed a
separate layer.


Aldrlch HPLC grade methylene chloride was used
in all formulations. Several different waxes were
used: a pure paraffin canning wax; a slightly
softer, lower-melting, microcrystalllne  wax (the
so-called "slack wax"); and simulated slack wax
that was prepared by mixing the paraffinic can-
ning wax and 5 to 20 percent hexadecane. Com-
mercially  available samples  of hydroxypropyl
cellulose (S23) and ethylhydroxyethyl cellulose
{SI05) were  used  as  thickening agents.
Hydroxypropyl  cellulose was favored because it
gelled more consistently in the presence  of
methylene chloride and other components or ad-
ditives. Unless  otherwise  noted,  the common
chemicals were purchased from Aldrlch or Fisher.
Surfactants were generally made available by the


Samples were evaporated from glass petri dishes,
approximately 9 cm In diameter and 1 cm deep,
that were topped with a slightly larger dish  or
loosely fitted cover. Samples were weighed on a
Sartorlus Top-Loading Balance. Model 1205 MP.
readable to 0.001 gram, that was interfaced to a
strip chart recorder (full scale = 2 grams).
    Since it was hard to take accurate weighings
In the fume hood, researchers put a baffle around
the petri dish. Initially, the baffle was made out of
a two-pound coffee can with a hole one Inch In
diameter In the top lid. Later, a similar baffle was
made of glass to enable researchers to observe the
surface of the sample during the evaporative

Evaporation Protocols

Initially, samples were shaken and then poured
directly into a tared dish on the balance. A timer
was started, the baffle set in place, and an initial
weight reading taken as quickly as possible. The
normal pattern of evaporation for samples that did
not contain wax was a rapid weight loss almost
linear with time. The rate loss persisted until the
sample had dried.
   When wax was in the formulation, the initial
period of rapid weight loss came to a fairly abrupt
halt and was followed by a much slower rate of
evaporation that remained  generally  constant
until  most of  the  methylene chloride  had
evaporated. Unfortunately, samples containing
wax showed very poor reproductibility, with great
variation in time to "shut down," the total weight
loss  prior to the shutdown, and in the rate of
evaporation after shutdown. Variations between
replicates of a factor of two, and sometimes sub-
stantially more, were not uncommon. Variations
were also seen in the surface films formed by
replicated solutions.
   Researchers worked diligently  to  find the
cause of variations between even essentially dupli-
cate samples. Insights about the barrier-forming
process gained from modifying evaporation tests
were incorporated Into test Protocol 1 and con-
firmed the  importance of wax film In controlling
the shutdown process. However, no real solution
was  achieved and Imprecision was a continuing
problem in assessing additive effectiveness.

• Protocol 1

Samples were shaken and poured Into a tared petri
dish set on the Sartorlus balance, the baffle was
set in place, and weight loss was recorded until 10
minutes after shutdown. Next, the petri dish was
covered for  10  minutes, then the cover was
removed and weight loss recorded again. The later
result (corrected for elapsed time) was taken as the
rate of evaporation.

• Protocol 2

At higher concentrations of wax or as more effec-
tive  additives were studied, Protocol  1 became
prohibitively slow.  To Increase productivity, a
number of chimneys  were  constructed  so 14
samples could be monitored simultaneously. In-
stead  of continuously recording  weight loss,
samples were weighed at 15-minute intervals for
two hours or more (if necessary) to achieve a total
weight loss of at least 0.1 gram.
    Replicate samples showed no consistent varia-
tion  with their position In the hood. Replication
was poorer than In Protocol 1 but still better than
experienced In the early stages of the project for
samples with lower evaporative losses.

                                                                      Reducing Risk In Paint stripping
Strippablllty Testing
Stripping evaluations on prepared test panels were
performed according to spot tests  described in
Robert Kodak's article (New Shelter, July/August
1983) on alkyd and urethane enamels.
   Five mL of stripper was placed on a test panel,
covered with a watch glass, and allowed to stand
20 minutes before a single pass scrape was made
to remove loosened paint and stripper.  Stripped
spots were evaluated visually, and the color of the
layer remaining was reported. In cases where the
paint was stripped to the primer, an estimate of
the primer area was reported, hi addition, the
degree of primer showing was determined by using
a wire grid (80 units per square Inch) and basing
the relative percentage of primer showing on the
relative percentage of grid openings that showed
   Direct comparison of results from the visual
and grid methods showed a less than 5 percent
variation. Resulting data showed a similar varia-
Test Panels

The panels were made from 6-by-12-inch pine
boards coated with four layers of either a good
quality alkyd enamel in one series or four layers of
a good quality commercial urethane enamel in a
second series. Each layer of paint was a different
color; the base primer coat was white. This made
the number of layers removed readily apparent.
   Several approaches were used to condition the
test panels. For one set, each layer of paint was air
dried prior to applying a subsequent layer. The
painted panel was then placed in a forced-air oven
at 110°C for 24 hours. A second set of panels was
prepared by successively air drying (24 hours) and
baking each applied layer overnight. For a third
set, each paint layer was air dried and the painted
panels were "aged" at room temperature for  10
weeks before being used.
Results and Discussion

The Experimental Matrix
The goal of the research was to develop a matrix of
data that detailed information on the evaporation
rate of methylene chloride In increasingly complex
mixtures of components—methylene chloride,
waxes and/or oils, thickening or gelling agents,
lower alcohols (methanol),  and toluene—that are
frequently found in commercial paint strippers.
The matrix was then expanded to include additives
that might reduce methylene chloride's evapora-
tion rate.
   The successive levels of the experimental
matrix, in order of increasing complexity, were as

    • Methylene chloride

    • Methylene chloride, wax

    • Methylene chloride, wax, gelling agent

    • Methylene chloride, wax, gelling agent,

    • Methylene chloride, wax, gelling agent,
     methanol, toluene.

   In addition to the main branch of the matrix,
studies were also conducted on the following mix-
tures that did not include wax:

    • Methylene chloride, gelling agent

    • Methylene chloride, methanol

    • Methylene chloride, gelling agent.

   At each  matrix level, additives  were  incor-
porated into the formulation to determine their
impact on evaporation rate. The additives studied
at University of Mlssourl-Rolla fell into four general
groups: five-membered  ring, heterocyclic com-
pounds; nonionic, surface-active chemicals; high-
ly oxygenated, simple organic compounds; and a
miscellaneous group of chemicals that were tried
mostly on an exploratory basis.

Methylene Chloride Studies

Much of the initial effort centered on developing
weight-loss  protocols. The weight-loss studies
were run as part of the overall data gathering effort
on the  first levels of the experimental  matrix.
Measured evaporation rates for  methylene
chloride alone were generally fairly uniform until
dryness for any given sample. A number of studies
were done in which the effect of a baffle, cover,
position within the fume hood, and other opera-
tional factors were evaluated. Overall, the
reproduclbility for methylene chloride alone was
fairly good. Actual results from a variety of test
situations  generally  fell within 26  to 31
mg/min/in2. The overall average (Table  1) was
29.1 mg/min/ln2.

Table 1.—Methylene chloride, wax solutions.






Methylene chloride
Methylene chloride
+ hexadecane
Methylene chloride
+ wax
+ wax
+ wax
Methylene chloride,
slack wax
+ wax
+ hexadecane
+ wax
+ hexadecane
+ wax
+ hexadecane
+ wax
+ hexadecane
















                                      18.8 -
Methylene Chloride—Wax

Samples containing wax exhibited a more complex
evaporation rate curve. There was
initial shutdown period prior to for-
mation of the wax barrier where the
evaporation roughly approximated
that of methylene chloride. After the
wax barrier had formed, a substan-
tially lower evaporation rate (steady
state rate) was observed. Again, this
evaporation rate usually persisted
for a substantial period of time.
    However, reproducibility of
evaporation rate measurements in
systems containing wax was quick-
ly found  to be problem.  Repro-
ducibility was a problem not only for
the  steady state  rate mea-sure-
ments but also for the length of time
prior to shutdown. In an attempt to
overcome this problem, researchers
tried a considerable  number of
weight-loss protocols. Replicate
samples from the same  master
solution could (at times)  exhibit
evaporation rates that differed by a
factor of 2 to 10. Unfortunately, no
simple cause (or, in turn, solution)
was  found  for  the  lack  of
    Increased  replication did help
in developing a useful database.
The overall experimental strategy,
as  noted previously,  centered  on
measuring the effect of individual
components or additives  on the
evaporation  rate. Within  the











framework of the experimental matrix, a consider-
able number of individual experiments was
designed to Illustrate the impact of small changes
in concentration of either additives or com-
ponents. Often these experiments seemed to sub-
stantiate the theory that changes in concentration
affected the evaporation rate.
    Sometimes  a  greater than  usual spread in
results brought into question whether a difference
in evaporation rate was associated with the vari-
able being tested. Rather than try to differentiate
or explain the differences in second order effects
as being associated with relatively minor changes
in concentration, the focus of this report was kept
on the broader concepts: between elements of the
matrix or "with versus without" comparisons for
    A wax level of 0.5 percent by weight seems to
be about as effective (Table  1) as  1.0 percent by
weight in reducing the evaporation rate. The single
data point for the 1.5 percent solution needs more
replication. However,  Figure 1  shows the shut-
     O  1% wax

     A  0.5* wax
i   i
                      I - 1 - 1 - 1 - 1 - 1 — L
                                                       8- 10  12  11  16  18
                                                              time, minutes
                         20  22  21  26  28  30 32
                                  Figure 1.—Evaporation rate—methylene chloride, wax solutions.

                                                                      Reducing Risk In Paint Stripping
down period was about one-third less with a 1.0
percent  wax solution  than with a 0.5 percent
   An attempt was made to see whether wax type
affects barrier quality. A highly refined paraffinlc
wax  and the so-called  "slack" wax are used In
commercial formulations; both are similar in that
they are composed of long-chained parafflnic
hydrocarbons. However, slack wax consists of a
broader  molecular weight range, and some of the
hydrocarbons present are normally liquid at room
   Slack wax was simulated in these studies by
using a mixture of paraffinic wax and hexadecane.
The latter was chosen to represent the liquid frac-
tion  in slack wax because It is  essentially non-
volatile.  Hexadecane did not contribute much to
the solubillzation of wax in these predominantly
methylene chloride  solutions as  the wax-
hexadecane solutions are normally cloudy.
   The  overall evaporation  rate averages for
paramnic wax and slack wax were 1.9 and 1.5
mg/min/in2, respectively (Table 1). While close,
the lower numbers for  cloudy hexadecane solu-
tions suggest that the closer wax is to its satura-
tion point in a formulation, the more readily the
barrier will form and its effectiveness improve. The
evaporation rate  for methylene  chloride
hexadecane solutions (Table 1)  were within the
range seen for methylene chloride alone.
   A number of additional experiments were run
(Table 2) that focused solely on components' effect
on the evaporation rate. Evaporation rate data are
shown for:

   • Methylene chloride alone,

    • Methylene chloride in binary mixtures
     with methanol or a gelling agent, and

Table 2.—Effect of wax In simple mixtures.







Methylene chloride
Methylene chloride
+ wax
Methylene chloride
+ methanol
Methylene chloride
+ methanol
+ wax
Methylene chloride
+ gelling agent [S23]
Methylene chloride
+ gelling agent [S23]
+ wax
Methylene chloride
+ gelling agent [S23]
+ methanol
Methylene chloride
+ gelling agent [823]
-I- methanol
+ wax





















    • A ternary mixture of methylene chloride,
      methanol, and a gelling agent.

    Data are also presented  for each  solution
where wax has been added as an additional com-
ponent that suggest mixing methanol and a gelling
agent affects (to a modest extent) the evaporation
rate of methylene chloride solutions that do not
contain wax. Obviously, from the data (Table 2),
wax is the key element in establishing the evapora-
tion rate, which is well understood within the paint
stripping Industry.
    Interestingly,  the  contribution  of methanol
and gelling agent seems to be observable even in
more complex solutions that  contain  wax. In
methylene chloride-wax  solutions, methanol or
the gelling agent (823) seem to contribute roughly
equally to reducing the  evaporation rate. Their
effectiveness seems to be additive as the combina-
tion of gelling agent, wax, and methanol drops the
evaporation rate another 0.9 mg/min/in2.

Surfactant Studies

The first class of additives studied were nonlonic,
surface-active  materials; Included  were  a
fluorlnated  compound  and various nonlonic
ethers and esters (Table 3). Some of these
materials, such as the sucrose esters, were recog-
nized by Cox in a British patent No. 1.023.213 as
being particularly effective  In reducing  the
evaporation rate for volatile organic compounds.
Most of the surfactants seemed to have some effect
(Table 4) in lowering evaporation as the observed
rates generally fell In the 15 to 24 mg/min/in2
    Of the materials  studied (Table 4).  only the
mixed sucrose esters Croda F-50  and F-110 and
sorbltan monostearate were effective in substan-
tially reducing the evaporation rate of methylene
chloride. Interestingly, only those sucrose esters
containing monostearate were effective in reduc-
ing evaporation rate. Likewise, monostearate was
effective while neither  the monopalmltate or
monooleate seemed to impact the evaporation sig-
nificantly. The monostearate  appeared to form
platelets on the surface.
    These results differ somewhat from the obser-
vations made by Cox for benzene-surfactant solu-
tions. The evaporation rate for methylene
chloride-Croda F-50 was one  of the lowest
recorded in the early stages of this study.
    An additional set of experiments were run with
methylene chloride and some pf the surfactants.
However, these tests (Table 5) also included 0.5
percent wax. The average evaporation rate for

Table 3.—Surfactants.
Crodesta F-10
Crodesta F-50
Crodesta F-110
Alkamuls SMO
Alkamide L7DE
Alkamide 1002
Arlacel 20
Arlacel 40
Arlacel 60
Arlacel 80
Brij 30
Croda Inc.
Croda Inc.
Croda Inc.
Alkaril Chemicals
Alkaril Chemicals
Alkaril Chemicals
ICI Americas Inc.
ICI Americas Inc.
ICI Americas Inc.
ICI Americas Inc.
ICI Americas Inc.
ICI Americas Inc.
Sucrose distearate
71/29 mixture of sucrose di- and mono-stearate
48/52 mixture of sucrose di- and- mono-stearate
Sorbitan monooleate
Lauric-myristic monoethanolamide
Coconut alkanolamide
Sorbitan monolaurate
Sorbitan monopalmitate
Sorbitan monostearate
Sorbitan monooleate
Polyoxyethylene (4) lauryl ether
Polyoxyethylene (23) lauryl ether
Table 4.— Methylene


chloride: surfactant studies.

Methylene chloride
Methylene chloride
+ surfactant additive
Zonyl FSN 100
Crodesta F10
Crodesta F50
Crodesta F1 10
Alkaril A1002
Alkaril AL7DE
Alkaril SMO
Arlacel 20
Arlacel 40
Arlacel 60
Arlacel 80






wax-methylene  chloride was 1.9 mg/min/in .
Neither of the  two Croda sucrose derivatives
seemed to be beneficial in that the evaporation rate
for these materials in wax-methylene chloride
solution was higher than the baseline rate.

 Table 5.—Methylene chloride, wax: surfactant

Methylene chloride
+ wax
Methylene chloride
+ wax
+ surfactant additive
Zonyl FSN 100
Crodesta F50
Crodesta F110
Arlacel 40
Arlacel 60







    Zonyl FSN-100 seemed to be very disruptive to
the barrier. One can speculate that the fiuorocar-
bon caused some "wetting" problems that resulted
in poor adhesion between wax platelets.
    Of the two sorbitan derivations tested, Arlacel
40 was much more effective than when present as
the sole additive in methylene chloride—1.1 ver-
sus 23.3 mg/min/in2. On the other hand. Arlacel
60, which was effective  in methylene chloride
alone, with an evaporation rate of 0.1 mg/min/in2,
seemed to be  less effective in the presence of
wax—0.7 mg/min/in2. The evaporation rate for
Aracel  60-methylene chloride-wax solution was
still lower  than that shown by the methylene
chloride-wax baseline measurements.
    The data suggest that the influence of large
surfactant molecules on the wax barrier can be
significant both in a positive or negative direction
in relatively simple solutions. They also Indicate
that the wax barrier formation takes place within
a small region near the surface and is Influenced
by the concentration of wax and  changing
solubility limits for wax in this region. The ability
of these large molecules to participate in barrier
formation in more complex solutions containing
gelling agents Is questionable.  The focus  of re-
search efforts at the  University of Missourl-Rolla
therefore was shifted  to smaller, more mobile

Additive Selection

In selecting additives that might desolubillze wax
and thus decrease the evaporation rate, attention
was next given to compounds that contained  a
high concentration of polar groups or groups that
might be capable of forming hydrogen bonds with
methylene chloride. The primary candidates were
alcohols, ethers, esters, and amines. Other than
the  shorter  alcohols and  amines, these com-
pounds are mlsclble with  liquid-saturated

                                                                      Reducing Risk In Paint Stripping
hydrocarbons and are not expected to be very
effective at desolublllzing wax.
   The flve-membered ring heterocyclic deriva-
tives were the first generation of the additives that
were studied. Prior studies of simple heterocyclic
compounds containing a carbonyl  functionality
had shown that they were capable of very strong
Intermolecular  Interactions,  perhaps stronger
than  conventional  hydrogen bonding,  as
evidenced by boiling points, in excess of 200"C.
Included in this group were Y-butyrolactone, 2-
pyrrolidone,  N-methyl  pyrrolidone,  and related
compounds. After this study had been underway
for some time, a patent was issued to Dow Chemi-
cal detailing the use of propylene carbonate as an
additive to reduce evaporation rate in paint strip-
per formulations. For comparison studies,
propylene carbonate was  included in the sub-
sequent test programs.
   During the course of these studies, the limited
mlscibility of methylene chloride and glycerine
suggested that glycerine might offer some unique
opportunities as an  additive. Glycerine, whose
density ranges between that of wax and methylene
chloride, might  also come out of a solution near
the surface and  provide a unique layer to comple-
ment the wax barrier. These considerations lead
to the inclusion  of  glycerine and the  related
ethylene glycol as the second generation of addi-
tives in this  research effort. The effectiveness of
glycerine also led  to studies with various
polyethylene glycols of different molecular weights
as well as a polyethylene glycol-methyl ether.
Finally, some experiments were run on amlne
additives. The polyglycol and amine additives were
considered the third generation of additives.

Methylene Chloride, Wax:
Additive Studies

The simple flve-membered ring heterocycles had
limited influence  on the  evaporation rate  for
methylene chloride (Table 6). This was also true in
more  complex  solutions  containing methanol
and/or a gelling agent (Table 7). Of the materials
studied, only propylene carbonate  seemed to
reduce the evaporation rate in methylene chloride
solutions without  wax that contained a gelling
agent and methanol.

Tables.—Methylene chloride: additive studies (no wax).
Table 7.—Methylene chloride, gelling agent, metha-
nol: additive studies (no wax).
Methylene chloride
Methylene chloride
+ -y-decanolactone
Methylene chloride
+ S-decanolactone


Methylene chloride
+ gelling agent [S23]
+ methanol
Methylene chloride
+ gelling agent [S23]
+ methanol
+ heterocyclic
A/-methyl pyrrolidone
Propylene carbonate
Methylene chloride
+ gelling agent [S23]
+ methanol
+ glycerine










    However, a  wide range  of flve-membered
heterocyclic ring derivatives appear (Table 8)  to
enhance the effectiveness of the wax barrier  in
relatively simple methylene chloride-wax solu-
tions. Although replication is insufficient, the most
effective additive was Y-decanolactone. N-methyl
pyrrolidone, butyrolactone, and  propylene  car-
bonate were equally as effective. All of these addi-
tives compared (Table 8) favorably against
methanol in reducing the overall evaporation rate.
The average evaporation rate for  this class  of
materials was 1.2 mg/min/in2 as compared to the
baseline without additives of 1.9 mg/min/in2.
Tetramethylene sulfone, succlnimide, and glycol
sulfite  were considered to be  marginal in their
effectiveness and not studied further.
Table 8.— Methylene chloride, wax: additive studies.



Methylene chloride
+ wax
Methylene chloride
+ wax
+ heterocyclic additive
N-methyl pyrrolidone
Propylene carbonate
Tetramethylene sulfone
Glycol sulfite
Methylene chloride
+ wax
+ methanol


0.5-1 .5








                                                    Some limited studies were done to see if paraf-
                                                 finic versus slack wax had an impact on  the
                                                 evaluation of the additives. None of the flve-mem-
                                                 bered ring compounds fared as well (Table 9) in
                                                 solutions  containing  8 to  12  percent of
                                                 hexadecane. The issue  appears to be  one of

solubility, with the hexadecane undoing (to some
extent)  the  polar  influence of the heterocycllc
derivatives. This Issue will be taken up again when
the experimental matrix Is expanded to Include
 Table 9.—Methylene  chloride,  slack wax: additive


Methylene chloride
+ wax
+ hexadecane
Methylene chloride
+ wax
+ hexadecane
+ heterocyclic additive
A/-methyl pyrrolidone
Propylene carbonate

0.5- 1.5
8 -12

0.5- 1.5
8 -12





 Experimental Matrix Studies

 The next level of experimental matrix to be studied
 consisted of rnethylene chloride solutions contain-
 ing wax and a gelling agent, hydroxypropyl cel-
 lulose (S23). In these studies, the level of S23 was
 kept  constant  at 1 percent while the  wax con-
 centration  ranged from 0.5 to  1.5 percent. The
 baseline evaporation rate for the three-component
 system was 1.26 mg/min/in2 (Table 10). All of the
 five-member  heterocyclic  derivatives studied
 (Table 10)  resulted in a substantial decrease in
 evaporation rate when Incorporated into the for-
 mulation at a level of 1.0 weight percent. In this
 phase of the study, N-methyl pyrrolidone and Y-
 butyrolactone gave the best results.
Table 10. — Methylene chloride, wax, gelling



Methylene chloride
+ wax
+ gelling agent [823]
Methylene chloride
+ wax
+ gelling agent [823]
+ heterocyclic
W-methyl pyrrolidone
Propylene carbonate
Methylene chloride
+ wax
+ gelling agent [823]
+ polyhydroxy
Ethylene glycol











    Results for the second generation  additives
were  even better. Solutions containing either
glycerine or ethylene glycol exhibited an order of
magnitude reduction In evaporation rate. While
the complexity of these solutions Is  relatively
modest as compared to commercial formulations
currently being sold by paint stripper manufac-
turers, these results were once considered very
promising and contributed to the continuation of
the sponsored research project for another year.
    The experimental program moved on to the
next matrix level with the inclusion of methanol in
the formulation. The only  component  that was
held constant in concentration was the gelling
agent (S23), at 1 weight percent. Wax was varied
from 0.5 to a high of 2.0 percent in one experiment,
while methanol ranged from 2.0 to 4.0 percent.
The baseline evaporation rate was determined to
be 0.46 mg/mln/in2 (Table 11) from a fairly large
number  of experimental  tests.  As a whole, the
flve-membered ring heterocyclic compounds still
appeared to contribute  to a reduction in the
evaporation rate with the overall average being
0.30 mg/min/in2.

 Table 11.—Methylene chloride, wax, gelling agents,
 methanol, additives.




Methylene chloride
+ wax
+ gelling agent [823]
+ methanol
Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ heterocyclic
W-methyl pyrrolidone
Propylene carbonate
Methylene chloride
+ wax
+ gelling agent [823]
+ methanol
+ polyhydroxy
Ethylene glycol
Methylene chloride
+ wax
+ gelling agent [823]
+ methanol
+ polyglycol additive
PEG 140
PEG 208
0.4-1 .0















                                                                       Reducing Risk In Paint Stripping
   In this series of tests, 6-decanolactone ap-
peared to be the best performer. Both of the second
generation additives continued to look good.
   Again,  for a fairly large number  of  tests,
glycerine solutions showed an average evaporation
rate of 0.13 mg/mln/ln2, while the corresponding
number for ethylene glycol was 0.20 mg/mln/in2.
Some limited testing with polyglycol derivatives Is
also presented (Table 11) and, in many respects,
the materials also look promising in these rather
elementary formulations.
   For both the flve-membered ring heterocycles
and the polyhydroxy compounds of the second
generation, the effect of the additives was less at
this matrix level (Table 11)—as compared to the
prior level (Table 10).
   Possibly this trend reflects the contribution
that methanol makes to desolubilization of the wax
without the presence of any additional additives.
The observed difference between the so-called first
and second generation additives  may be a result
of the "liquid" barrier. These results suggest that
additives  such as  the  five-membered  ring
heterocycles, which  seem  to rely primarily on
reducing the solubility of wax, will at best be only
marginally effective in high "methanol" paint strip-
per formulations—that  is, formulations  with
greater than 10 percent methanol.
   The next matrix level studied in this laboratory
program involved the addition of toluene to the
formulation. While both  toluene and methanol
content were varied within limits, these experi-
ments did feature fixed concentrations of wax and
gelling agent at 1.0 weight percent. Toluene was
Included In the matrix because it has been found
In commercial formulations and it represents a
wax "solubilizer" as compared to methanol, which
is believed to  reduce the solubility of wax. The
baseline evaporation  rate developed for this five-
component matrix was 0.41 mg/min/in2 (Table
12) and differed only modestly from the baseline
observed for solutions that did not contain toluene
(Table  11).  While  the flve-membered  ring
heterocyclic derivatives still showed some ability
to reduce  the evaporation rate,  the gap with
baseline results narrowed considerably (Table 12
versus Table 11). The effectiveness of glycerine was
also less in solutions containing toluene; however,
there was still a 50 percent reduction as compared
(Table 12) to the baseline measurement.
   Results for ethylene glycol solutions were ex-
pected as they exhibited highly elevated rates as
compared to the baseline solutions. The reason for
these results is unclear, although the trend agrees
with the earlier slack-wax studies. Perhaps In the
presence of wax solubilizers, higher additive levels
Table 12.—Methylene chloride, wax, gelling agents,
methanol, toluene, additives.




Methylene chloride
+ wax
+ gelling agent [823]
+ methanol
+ toluene
Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ toluene
+ heterocyclic additive
A/-methyl pyrrolidone
Propylene carbonate
Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ toluene
+ polyhydroxy additive
Ethylene glycol
Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ toluene
+ polyamine additive
Triethanol amine














are needed to impact the evaporation rate. Yet, the
baseline data do not suggest that toluene weakens
the evaporation barrier.
   Some additional experiments are reported on
tests involving the use of polyfunctlonal amines as
additives. While the data (Table 12) appear to be
comparable to those recorded for glycerine solu-
tions, other observations bring into question the
use of amines in this application. Specifically, the
solutions  appeared  to  "salt-out"  on standing.
Speculation postulated that the amines catalyzed
the hydrolysis or reacted with methylene chloride
with   the  resultant  formation  of  amine
hydrochlorides. Since  commercial formulations
must  exhibit long-term stability,  no further
studies were performed with amine additives.

Thickening Agent Comparison

The final set of studies within the matrix Involved
a comparison of  gelling  agents. The thlxotropic
agent used In most of the laboratory studies was
hydroxypropyl cellulose (S23).  Comparative runs
were made with another gelling agent,  ethylcel-
lulose (S105). both with and without glycerine. In

these experiments, comparisons were made both
for methylene chloride/wax/gelling agent/metha-
nol and methylene chlorlde/wax/gelllng agent/
methanol/toluene solutions.
    For the purposes of this segment of the study.
the data were combined (Table 13) without factor-
Ing In the presence or absence of toluene. In both
comparisons,  solutions  containing   the
hydroxypropyl cellulose (S23) thickening agent ex-
hibited lower evaporation rates than were seen for
formulations containingethylcellulose (SI 05). The
effectiveness of glycerine as an additive was mar-
ginal in these experiments. A substantially better
reduction was noted earlier (Table 12) with similar

Table 13.—Gelling agent studies.




Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ toluene
Methylene chloride
+ wax
+ gelling agent [S23]
+ methanol
+ toluene
+ glycerine

Methylene chloride
+ wax
+ gelling agent [S105]
+ methanol
+ toluene
Methylene chloride
+ wax
+ gelling agent [S 105]
+ methanol
+ toluene
+ glycerine





1 .0-2.0








 Commercial Formulations

 The real  test for any additive would be in its
 successful incorporation in a commercial stripper
 formulation.  The program was not designed to
 develop a "commercial" formulation nor to break
 down the many possible combinations used today
 In commercial paint removing products. To gain
 an insight as to whether the additive concept could
 be employed commercially, glycerine was added to
 three formulations. As seen In the resultant data
 (Table 14), there Is a substantial variation in the
 evaporation rates of the commercial stripping for-
 mulations. In one case (Formulation B), the addi-
 tion of glycerine substantially Increased  the
 observed evaporation rate. However, Formulation
 B already exhibited an evaporation rate substan-
 tially higher  than most of the "model" formula-
tions. Two other commercial products (A and C)
exhibited low evaporation rates. Although the level
of replication was insufficient to draw firm con-
clusions, there may have been  some additional
reduction of evaporation rate because of the addi-
tion of glycerine.

 Table 14.—Commercial formulations.



Formulation A
Formulation A
+ glycerine
Formulation B
Formulation B
+ glycerine
Formulation C
Formulation C
+ glycerine









Stripping Effectiveness

Some variations of cure conditions for test panels
used In this study were noted previously. There
was some concern whether differing conditioning
protocols would significantly affect the outcome of
the stripping tests.  A series of test panels were
tested for strlppabllity by a commercial stripper.
These test panels included:

    •  A one-year-old panel In which each layer
      was oven-baked for 24 hours before a
      subsequent layer was applied;

    •  An air-dried, 10-week-old test panel; and

    •  An oven-baked. 10-week-old panel in
      which each coating layer was air-dried for
      24 hours before a subsequent layer was

    Stripping rates were determined for alkyd and
urethane coatings, two ratings (Table 15) for each
test. The first number represents a visual estimate
of the percentage of white primer visible after the
stripping solution was scraped from the surface.
The second number represents an attempt at a
more quantifiable estimate in which a wire grid (81
units per square inch) was placed over the test
area and ratio grid units showing white to the total
number of grid units in the stripped surface area
was calculated. While the two results  are com-
parable, the grid unit seems to result in a lower
estimate of effectiveness. The mode of preparation
for alkyd test panels seems to have minimal effect.
Somewhat surprisingly,  the urethane panels
prepared by air drying between the application of
each coating layer with subsequent oven-drying of
panels were the most difficult  to strip.
    Stripper tests were also run for model formula-
tions  containing methanol and glycerine (Table

                                                                       Reducing Risk In Paint Stripping
 Table 15.—Test panel conditioning: stripping tests.
Oven-baked, 1-yr. old
Air-dried, oven-baked, 10-weeks old
Air-dried, 10-weeks old
100 (96) 90 (90)
100 (98) 70 (65)
100 (95) 90 (88)
 "The first number of each pair is a visual estimate, while the second number
 is a calculated ratio from reading a grid.
16). The formulations tested consisted of
methylene chloride, wax (1 percent), and thicken-
ing agent (1 percent S23), along with the specified
levels of methanol and glycerine. These results
suggest that glycerine can contribute to the effec-
tiveness  of the stripper. The ratio of glycerine
relative to methanol Is Important; a  1  percent
glycerine, 4 percent methanol formulation may be
 Table 16.—Stripping tests: methanol, glycerine

50 80
99 (a)
90 40
95 50
100 100
85 20
 (a) wood grain visible
             optimum. As expected, alkyd test panels stripped
             easier than urethane coatings.
                 A more extensive series of formulations con-
             taining flve-membered ring heterocycllc com-
             pounds and glycerine were tested next  for their
             strlppability. The formulations that were chosen
             exhibited  an  evaporation rate  below 0.20
             mg/mln/ln2. These test formulations (Table 17)
             Included wax (1 percent), thickening agent (1 per-
             cent S23), and specified levels of methanol and
             toluene. Unlike the prior study, results for none of
             the additives were as good as the baseline results.
             Again, these formulations included toluene, which
             was shown to negatively affect the additives' ability
             to reduce the evaporation rate.
Conclusions and

The  testing  program included alcohols (wax
desolubllizers) and hydrocarbons (wax solubi-
lizers). Many commercial formulations also In-
clude activators and surfactants to enhance the
onset of the stripping process and aid in removing
stripping residues. Extension of the matrix to in-
clude activators and surfactants would be valu-
   The experimental data Indicate the effective-
ness of additives Is moderated as the formulations
become more complex. Each component in the
formulation can affect the effectiveness of the ad-
Table 17.—Stripping tests: methanol, toluene formulations.

/V-methyl pyrrolidone
Propylene carbonate



















dltlve.  One of the critical factors is the balance
between  polar and nonpolar solvent functions
within the formulation. Taken in total, the work
strongly suggests that an additive approach can
contribute to a reduction in evaporation rate.
   Of the additives studied, glycerine seems uni-
que in that it may, because of its limited solubility
in methylene chloride, provide a liquid barrier to
complement the more usual wax barrier. The other
five-membered  ring heterocyclic compounds
studied also appear to have  some potential  in
reducing the evaporation rate of methylene
chloride. Their performance should be equivalent
to that provided by propylene carbonate, which
has been patented by Dow Chemical Company for
this end-use application. Of these materials, N-
methyl pyrrolidone seems to have the most poten-
   Since there is considerable variety in formula-
tions used in paint remover products In the United
States, it is apparent that these additives must be
tested  within the framework of the individual
manufacturer's formulations. To this end, Vulcan
Chemicals and Occidental Chemical have entered
into an agreement with the University of Missouri
to facilitate the evaluation of these additives by
paint remover manufacturers.

                PAINT  STRIPPING
            Questions Si Discussion
      Discussion in the Household and Commer-
      cial sessions focused on consumer
      sophistication in using paint strippers,
the safety of substitute strippers, and methods of
pollution prevention and exposure control. Dis-
cussion in the first breakout session focused on
consumer end-uses of strippers and the extent to
which consumers are aware of the types of coat-
ings that they are removing. The discussion was
prompted by a suggestion that different stripper
formulations could be marketed for the removal of
different coatings.  Participants noted that the
primary obstacle to this is limited consumer
knowledge of the coating being removed. In addi-
tion, the area or item to be stripped is often covered
by several layers of possibly different coatings,
making it impossible for even the most informed
consumer to determine the suitability of a par-
ticular stripper.
   Questions following the substitute formula-
tion presentations  on Tuesday afternoon were
aimed at the appropriateness of labelling any paint
stripper as "safe."  Sandra Eberle of the  CPSC
pointed out that, in general,  disclaimers are not
permissible In labelling under the Federal Hazard-
ous Substances Act (FHSA) and that there is no
official definition of "non-toxic." The discussion
pointed  to a general dissatisfaction with the
amount of Information available on the safety of
substitute paint strippers. Other comments were
made about rinsing the substrate with alcohol
when applying NMP-based strippers. Gerald L.
Bixenman noted that there was a contradiction in
marketing NMP products as non-flammable while
simultaneously recommending the use of a highly
flammable alcohol rinse with the stripper.
   Wednesday's first presentations in the
household /commercial session was followed by a
discussion of an integrated approach to pollution
prevention. Some proponents of methylene
chloride-based strippers maintain that little waste
is  generated in using these strippers  since
methylene chloride evaporates, leaving only dried
paint to be landfilled. Ed Balrd of Wilson Imperial
pointed out that evaporated methylene chloride
should not be thought of as disappearing, since it
remains in the air. Janet Hickman of Dow Chemi-
cal added that the ideal control system would be
one in which the stripping material is recovered
and prevented from going into the environment.

Also in this session, trends In coating and strip-
ping were discussed. Nancy Llndqulst, a profes-
sional finisher, remarked that  there Is a trend
towards tougher and tougher coatings and a con-
current trend towards weaker and more benign
strippers. This poses  challenges to the stripper
Industry, particularly In the removal  of
polyurethane coatings.
    In the final session, questions predominantly
concerned Cheryl Fairfleld's presentation of en-
gineering controls for furniture stripping. Several
people expressed interest in the details of the
NIOSH study and the costs of implementing the
controls described in the study. Cheryl Falrfleld
said that the details of the study will be published
and a pamphlet will be produced for furniture
strippers. Mechanical barriers to exposure control
were  also discussed.  Gordon Bock of the Old-
House Journal asked if anyone had experimented
with mechanical barriers to control evaporation.
Michael Clarkson said that this type of system had
been tried in the UK. but that consumers had some
difficulty using it.

        Chair: Mary Ellen Weber
    Director, Economics and Technology Division
        Office of Toxic Substances
      U.S. Environmental Protection Agency

Panel  Reports:  Summary  of Findings
Christine Wh maker
Office of Risk Reduction Technology
Health Standards Division
U.S. Occupational Safety and Health Administration
James Gideon
Division of Physical Sciences and Engineering
National Institute for Occupational Safety and Health
Washington, D.C.
Sandra Eberle
Program Management and Budget
U.S. Consumer Product Safety Commission
Washington, D.C.
Original Equipment

• Christine Wh Maker
To summarize the major themes that were ad-
dressed in our panel sessions, I would like to begin
by considering what would be the characteristics
of a perfect paint stripper. Based on the applica-
tions described for OEM paint stripping, such a
substance or process would have good stripping
effectiveness on a wide variety of coatings; it would
be both fast and complete In Its stripping action;
It would be low cost, have low toxlclty, and be
effective on both  new and old paint films and
coatings; It would have no odor and would be
completely non-flammable. Unfortunately, there is
no perfect paint stripper. The best paint stripping
product or process will be different for each ap-
plication. All of the alternatives discussed in the
OEM sessions have trade-offs with respect to ap-
plicability,  effectiveness, and cost. The goal in
selecting the correct  process is to optimize the
formulation or technique for the requirements of
particular paint stripping applications.
   We can review several major themes that were
discussed in the OEM panels.
   No one single method of stripping paint is Ideal
for every paint removal application.
   For example, cured paints pose very different
technical requirements for effective removal than
do uncured paints. Combinations of several
methods (hybrid techniques) for effective removal
are sometimes much more efficient with respect to
both cost and performance than a single method
alone. We heard about the combined use of chemi-
cal strippers and plastic media blasting, very cold
liquid nitrogen accompanied by plastic media
blasting; sponge blasting with chemical stripper;
and the use of coatings and water rinses.
   For substitute chemical solvent formulations,
we can conclude that there are some promising
substitutes, including NMP, though at this time
they may be quite expensive. The challenge for
chemical formulations is to devise a formulation
which reduces cost and still maintains stripping
effectiveness. For mechanical strippers, there are
some limits to the processes' applicability. These
limitations are a function of both substrate com-
position and the type of coating to be removed. This
may, of course, be equally true for chemical strip-
pers. For example, we heard that Ultra High Pres-
sure Water may best be used on steel, Iron, and
equivalent substrates; cryogenic systems work
best on thicker coatings, and may not be  ap-
propriate for some soft substrates.
   Other stripping methods described In the OEM
sessions Included the use of barrier coatings—
protective covers—that are water rlnsible. These

coatings are particularly suitable for use to remove
overspray in paint booths.
    In addition to stripping effectiveness, a num-
ber of other issues are Important to the evaluation
of paint stripping processes. The time required for
stripping, for example, Is an Important considera-
tion. Substitute stripping methods, although not
as fast as methylene chloride, seem to be effective
within an acceptable time period. Paint stripping
methods vary widely with respect to type and
extent of costs incurred. Chemical solvents can be
costly to purchase  on a regular basis, while
mechanical strippers may have  a large capital
outlay to finance equipment purchase. Recycling
of methylene chloride strippers may reduce en-
vironmental releases and improve cost profile.
    Concerning toxiclty, one Interesting address
highlighted several approaches to reduce volatile
organic releases that can be used without Incur-
ring appreciable added costs or process changes.
Among these were a reduction in volume of strip-
per used, which may be accomplished  through a
change In the method of stripper application. For
example, thlxotroplc strippers may adhere to sur-
faces better, or the use of spray instead of mop and
bucket may provide more efficient coverage for
certain paint clean-up operations. Finally, In some
cases, it  may be appropriate to replace some sol-
vent use with water-based barrier coatings.
 Maintenance Paint Stripping

• James Gideon
The objective of paint stripping is to remove the
coating while leaving the substrate intact. There
are a series of constraints in this process, includ-
ing air and water pollution, generation of solid
waste,  protection of workers,  and  cost. Paint
removal involves an inherent contradiction be-
cause  coatings  are getting tougher while sub-
strates are often becoming thinner  or use more
exotic materials, such as fiber-reinforced epoxy. A
safe removal method must have a fundamentally
different effect on the coating than  on the sub-
    Paint can be removed  In several ways. The
time-honored method Is to degrade the coating by
using  a solvent such as methylene chloride, a
traditional baseline stripper. Our session only
touched on the other solvents; primarily, we dis-
cussed a variety of mechanical methods. Including
dry media blasting techniques that use wheat
starch and plastic media; two hybrid systems, COa
pellet blasting and Ice blasting; and  two wet sys-
tems, the high-pressure or ultra high pressure
water technique and slurry blasting, using sodium
    In addition, we have discussed applying ther-
mal energy to coatings through flash lamps—es-
sentially a high-intensity, pulse-light infrared
source of energy that has been used commercially
on buildings, steel structures, and some aircraft—
and lasers that, given a precise control of
resonance, time, and temperature, are potentially
capable of removing coating.
    Our session indicated that there are probably
more questions than answers, since many of these
technologies are  under development or applica-
tion. We do not have a great deal of Information on
either cost or removal rates for specific systems.
both of which vary from case to case. Although it
may be  difficult to collect definitive Information.
these data are needed to make decisions.
    Another area Is waste management. A spokes-
man from the Department of Defense talked about
efforts to reduce removal wastes by recycling, sub-
stituting, or concentrating waste streams. An In-
novative method uses  genetically engineered
microbes to blodegrade various plastic media and
some paint residue. Another presentation dis-
cussed the recovery of methylene chloride vapor
with fixed systems and others that are potentially
    After reviewing the technology, we decided that
the paint removal industry faces the following

    • The industry should determine the
      long-term effects of the various techniques
      on  the  substrate. This information  is
      critically Important when selecting a viable
      paint removal process in the aerospace
      Industry since aircraft are made of thin
      metal skins. It may be difficult to evaluate
      subtle effects that occur over time; however.
      this issue has  underlined  airlines'
      conservative decisions when picking new
      paint-removal methods.

    • Manufacturers  must compile  good,
      objective Information on cost, productivity,
      and  how well (given differing techniques)
      these methods work to remove paint In a
      given situation.  No one paint stripping
      method is the panacea; therefore, a number
      of techniques will develop specific market

    • Industry should address the increasing use
      of composites  and high  technology
      materials in airplanes and the challenge of

                                                                     Reducing Risk In Paint Stripping
     selecting a paint removal method that will
     be  compatible—as well as a method for
     existing older airplanes for  which the
     composite components have become more

   • Manufacturers and  consumers should
     recognize  that a synerglsm  may exist
     between technologies. For example, in one
     case, paint was chemically softened and
     then removed by  high pressure water
     blasting. Because there are fundamentally
     different approaches for removing coating,
     it may be possible to apply more than one
     technique sequentially to do the best Job.

   • The industry's continued use of automated
     paint  removal systems can  potentially
     protect workers, increase productivity,
     provide consistency that comes from
     robotics,  and lower  costs.  This  is
     particularly true in the aerospace industry
     where it may be possible to strip many of
     the same types of aircraft  in one facility.
     Despite higher capital costs, it might be
     viable to construct larger facilities  that
     could service many airplanes.

   • An exciting prospect is the use of a systems
     approach designed to rethink the protective
     coating system  on  airplanes or other
     vehicles over the life  cycle of  the coating
     system. It may be possible to optimize both
     the protective features of the coating and
     the ability  to safely,  easily, and  cost
     effectively remove it if both coating efficacy
     and removal are considered  as  design
     parameters of a completely new system.

Comment (Carmine Carbone): It would be helpful
to have capital expense costs and  operating costs
Included  in the summary report. Also, I'd like to
define the components that  make up these costs
and  scale them  to  narrow- and wide-bodied
Household and Commercial

• Sandra Eberle
As I sit here and listen to my colleagues discuss
what went on in their sessions, I hear a lot of
similarities. Many of the same challenges are con-
fronting these people. In the consumer and com-
mercial market, the challenges from the furniture
refinlshers and professional restorers are no
greater than stripping wide-bodied airplanes of
delicate construction. They include a number of
issues that focus on consumer acceptance and
both personal  and household safety. Examples
include refinishers who have their children in
playpens in the area where they work and small
commercial shops where children work side-by-
side with their parents. Participants have environ-
mental concerns about  waste and air emissions
and also others about material costs in terms of
time and  labor. Foremost,  however, we  heard
about new products.
    We were very fortunate in our panel members.
They included  professional refinlshers and more
than a few homeowner users; major chemical com-
panies, who spoke about basic research; and for-
mulators,  the people who work on new product
ideas. A lot of special needs  have to be met for
acceptance in this  consumer and commercial
reflnishing market.
    I'd like to touch on a couple of themes. First,
the barriers to product development that might, in
another area, be called research needs. There's a
lack of uniform information on product safety—on
the toxlclty of various ingredients. Each individual
formulator seems to be seeking this Information
from different sources and having different degrees
of success. The data may exist but certainly are
not readily available.
    Safety and toxlcity data, if they exist, are open
to interpretation. There is no baseline of uniformly
agreed-upon standards on what Is hazardous or
safe—not even for flammability.
    The other barrier to product development is
the inconsistency in testing information. Products
were tested on a variety of substrates; however,
removal codings were not uniform. The age of the
coating is important, as is the arrangement of the
layers and the nature of different coatings.
    Although certain inconsistencies exist in the
basic types of strippers, formulations are not
uniform. Manufacturers use different activators as
well as varied amounts of chemicals In the for-
mulations, which makes it difficult to compare a
company's work on a methylene chloride-based
formulation versus one containing dibasic esters
or Jtf-methyl pyrrolidone. Everyone is testing them,
but they are all testing different formulations so
conclusions are inconsistent. A lot of work has
gone Into optimizing certain formulations, and
those products' effectiveness is close to if not the
same as that of methylene chloride-based formula-
tions. Again, that conclusion is complicated by the
lack of testing uniformity.

    Mark Greenfield said that we are all environ-
mentalists, and certainly that came through from
each panelist and presenter. There is a concern
about the environment but no uniform level of
knowledge, understanding, and acceptance.
    The history of the development of paint-strip-
ping formulations goes back well before benzene
strippers. Manufacturers have made a consistent
effort to refine formulations and meet safety and
health needs.  The more durable  coatings being
used on furniture require new innovations in strip-
ping formulations. An emerging new issue is the
danger to humans from lead-based paint in hous-
ing. There will be a greater need to strip architec-
tural  elements such as window frames, panel
doors, and even walls in dwellings.
    All these new products must be accepted by
consumers and professionals, who share a unique
problem: often the nature of the substrate is un-
known. Delicate veneers,  exotic woods,  or ivory
inlay may lie beneath those layers of coatings. The
furniture restorer and successful consumer-user
do not want to damage that substrate, so they have
to be sure the paint stripper will not harm the wood
itself or the glues.  The consumer has different
preferences and experiences other problems than
the professional.  If professionals can identify the
coatings, they may be  able to use specific strip-
pers. Even if consumers can identify varnish, they
may not be able to pick a specific varnish stripper.
So  while specialized products may be appropriate
for the commercial  professional, the consumer
probably needs a product  with  a fairly broad
    Consumers really hate stripping;  it's messy,
smells bad, and  taking these multiple layers of
coatings off is unpleasant, hi that context, strip-
ping is Just one part of the process but not an end
in itself. The consumer refinisher faces multiple
issues: whether  to  darken or stain  the wood,
problems with bleed through, and the stripper's
impact on any new  finish. All of this should be
taken  Into consideration when  manufacturers
develop new products.
    Working time, especially for the professional,
is important in terms of acceptance. New products
that require more time than traditional ones have
to overcome consumer expectations about strip-
ping speeds. Consumers also expect to see blister-
ing and lifting; many  new products just soften
paint. Lastly,  if the  consumer cannot use tradi-
tional tools, that's another detriment  to the new
    In  the commercial market, traditional equip-
ment Includes pumps  and vats.  Changes that
would vastly  reduce exposure and costs while
providing more worker and environmental safety
would be necessary for new products.
    In terms of safety, the professional faces Issues
of equipment, changes in process, engineering
controls, worker protection, and the adequacy of
information about protection. Other issues in-

    • Respirators—are they effective when
     working with traditional methylene
     chloride paint strippers?

    • Flammability;

    • Lead paint abatement;

    • Worker safety;

    • Child safety (basic contact with the
     product or fumes);

    • Toxlclty, both acute and chronic;

    • Use of products indoors or in an enclosed

    • Labelling. CPSC is surveying to find out if
      consumers read and heed labeling on
      methylene chloride-based paint strippers.
      To what extent are labels effective in
      changing consumer behavior?

    • Eye and skin irritation. The basic issue of
      exposure is that, all other things being
      equal, the user will have a greater risk
      from the more volatile substance than
      from the one that is less volatile even if
      toxiclty is the same.

    • The consumer's ability to follow
      directions. Can consumers use caustics
      and acids safely? A certain amount of
      market history says they will; however, a
      certain amount says there's  a possibility
      of very serious injuries.

    • Environmental concerns, an area where
      there Is the most need for follow-up

    • Waste, be it waste into sludge streams
      and landfills or emissions into the air.
      Very little cognizance is being taken of
      concern about emissions into the air and
      recovery of solvents. Materials often
      require testing to determine  whether they
      are a hazardous waste and then need
      specialized treatment;

    • Communication between formulators and
      users, both small shop or commercial
      refinishers and householders. What Is

                                                                  Reducing Risk In Po/nf Stripping
expected of them If they're going to be
good environmental citizens?

Vapor recovery, the whole issue of volatile
organic compounds.

Costs: the cost of the materials versus the
amount of the material used; costs of
labor, of application time and waiting
time; costs in terms of profit margin In the
distribution chain; and cost of waste
disposal and emission control. Certain
new product applications include being
able to estimate, consistently, costs for
labor, disposal, and material.

New products. Everybody, unfortunately,
is testing something different on
something different. Major types of new
products include the dibasic esters,
N-methyl pyrrolidone, traditional
      flammable paint stripping products,
      caustics, and DCM products. Among the
      new methylene chloride products are
      various vapor-retardant systems, barriers,
      glycerins, waxes, additives, gel resins, and
      innovations that would lessen exposure
      from the use of DCM products.

    •  Lastly, new problems. Manufacturers are
      developing new coatings that are difficult
      to remove, such as polyester, some of the
      acid-catalyzed coatings, and certain

    I would echo the other chairman in saying that
we  had a great group  of people. They were  a
resource not  only when they were speaking but
also as an audience.  It is clear that many issues
need  further  research and that solutions have
been only partially achieved.

The  Next Steps:  Planning  for the  Future
Katy Wolf
Institute for Research and Technical Assistance
Los Angeles, California
• Mary Ellen Weber
Dr. Katy Wolf is the director of the Institute for
Research and Technical Assistance, a nonprofit
organization that provides technical information
and helps  demonstrate  new technologies.  Her
focus is on industries that use chlorinated sol-
vents and other ozone-depleting chemicals. For
the last three years, Katy has been looking at over
14 industries and analyzing reduction of
chlorinated solvents.
    Before that, Katy Wolf was a researcher at the
Rand Corporation, where she  worked on use,
release, and control measures for ozone-depleting
substances in chlorinated solvents. Katy has her
B.S. in chemistry, her M.S. in physical chemistry,
and a Ph.D. in chemical physics; in addition, she
teaches at U.C.L.A. I would  like to present Katy

• Katy Wolf
I'm glad to be able to speak to you. As you heard
from the short biography, halogenated hydrocar-
bons are my life; I have worked on chlorinated
solvents and other ozone-depleting substances for
much of my career. They're very interesting. I'm
excited about working in all of the industries where
these substances are used.
    Before I begin, I'd like all of us to thank the
EPA for putting on this excellent conference. It has
been extremely useful for sharing information
about paint stripping. I want to urge EPA to put
on conferences focusing on other end-use areas
for chlorinated chemicals.
    Many people have asked me throughout the
conference if anyone had data on using methylene
chloride. Production of methylene chloride domes-
tically in 1988 amounted to about 229,000 metric
tons.  Demand—which is equal to  production
minus exports plus imports—amounted to some-
what less, 207,000 metric tons. That figure will
vary on yearly, depending on whether exports
exceed imports.
    Methylene chloride has various end-use ap-
plications, the largest being paint stripping. It is
important to note here, too, that methylene
chloride is a ubiquitous solvent; It's used widely in
a whole  range of different applications. The
category  called "other" is very, very large and
composed of a number of different applications.
    Of the 50,000 metric tons of methylene
chloride used for paint stripping, 10,000 metric
tons  are consumed  in original equipment
manufacture; 20.000 metric tons in military (the
majority), commercial, and other applications; and
20.000 metric tons by consumers. Paint stripping
by householders accounts for about two-thirds of
total consumer use,  with contract stripping by
outside furniture refinlshers accounting for the
remaining third.
    Methylene chloride blended with other com-
pounds makes an excellent paint  stripper.  It
penetrates the cured film paint matrix readily,
bubbling up the material;  with the addition  of
other chemicals, it can remove all kinds of coatings
very quickly,  even  epoxy-based primers and
polyurethane topcoats on military vehicles.
    Methylene chloride provides two environmen-
tal benefits. Since it does not have a flash point,
It's not flammable. Virtually all of the alternatives
have flash points, either in the flammable or com-
bustible range. Also, methylene chloride does not
contribute to photochemical smog, so under sec-
tion 111  of the Clean  Air Act, it is an exempt
material and is usually  exempted by local air
districts. So firms, to avoid using photochemically

                                                                      Reducing Risk In Paint Stripping
reactive substances, have turned to methylene
   There has been some discussion over the last
few days about the regulatory regime that sur-
rounds  methylene chloride. I will briefly sum-
marize the information.

   • Although  the results  remain extremely
      controversial,  methylene chloride has
      tested positively in carclnogenicity trials
      with certain animal species. Whether or not
      those data are translatable to human beings
      remains controversial.

   • The  Occupational Safety and  Health
      Administration will promulgate a proposed
      rule to lower the workplace exposure level
      significantly, from the current level of 500
      parts per million to 25 parts per million.

   • The   Consumer   Products'   Safety
      Commission required labeling in the past
      but has made It  voluntary. Household
      products that contain methylene chloride
      should be labeled.

   • Under the Clean  Air  Act Amendments,
      methylene chloride has been designated a
      toxic air contaminant. It's not clear yet what
      that will mean, except that, over the next
      seven  years,  regulations  will  be
      promulgated for paint stripping and other
      sectors that use methylene chloride.  It's
      likely that certain control technologies will
      be required, depending upon the Industry
      where the substance is used.

   • EPA may also require industries using the
      substance  to adopt maximum available
      control technology (MACT).

   • The California Air Resources Board has also
      designated methylene chloride a toxic air
      contaminant. Over the next few years, they,
      too,  will  be requiring  use of  control
      technology in various end-use sectors. In
      California,  methylene chloride  Is also
      named under Proposition 65, which lists
      chemicals known to cause cancer and birth

   • Finally,  in  California, the Southcoast Air
      Quality Management District is passing a
      new rule that will affect methylene chloride
      users, particularly In the paint stripping
      category. Users calculate  whether or not
      they exceed the allowable risk level—10"6 at
      this stage. If they do (and it's very likely that
      paint stripping operations will), then they
      are required to put  in what's  called
      T-BACT."  toxic  best  available control
      technology. However, the district has not
      defined what T-BACT is for any Industry,
      which must be done before the rule becomes
      effective.  Users that exceed the risk will
      spend money on a control technology that
      might be denied a permit. The district has
      already started levying a fee of 19 cents a
      pound on methylene chloride users, which
      is  significant because  the  bulk price of
      methylene chloride Is 29 to 30 cents per

    Some of the trends in the  paint stripping in-
dustry that have occurred and some that can be
predicted for the near future Include:

    • Movement away from  use  of methylene
      chloride by many auto production firms
      because  of  pressure from unions and
      workers. They still use methylene chloride
      in  various applications  where  alternatives
      are hard to find.

    • The new OSHA permissible exposure level
      will move firms away in all sectors because
      25 parts  per million is an  extremely low
      exposure level. Ventilation levels In the
      workplace will have to  be raised to meet
      those standards. It's not clear yet whether
      OSHA will promulgate a proposed rule that
      will allow  use of  personal protective
      equipment for a few years and then require

    • The OSHA regulation and the Clean Air Act
      Amendments  and state  and  local
      regulations requiring control technology of
      various kinds will be extremely significant.
      The interaction between the  new  OSHA
      permissible  exposure  level and control
      technology is also important. The higher the
      air flow in the workplace, the larger the air
      stream that must be treated for a control
      technology, making it extremely expensive.
      Furniture refinishers can certainly Increase
      the airflow in the workplace, but they may
      not be able to afford the control technology
      required under  the  Clean Air  Act
      Amendments or local regulation.

    In the original equipment manufacturing sec-
tor, there are four basic end uses for methylene

    • The first  is booth stripping, which is done
      in many auto assembly facilities and other
      plants  with assembly  lines.  Parts move

      through a paint booth  on racks and
      hangers, and a worker sprays them with a
      paint gun.  The paint that is oversprayed
      onto the sides of the  booth is removed
      periodically—that's booth stripping.

   • When workers change the type or color of
      the paint, they have to clean the guns and
      lines—another  end use of methylene

   • Paint that is dropped on the floor must also
      be cleaned up periodically.

   • Finally, methylene  chloride is used  in
      immersion stripping for racks, hangers, and
      hooks that  are  caked with paint and
      rejected parts that need to be worked.

   Firms can use many alternatives to methylene
chloride when booth stripping because the paint
is usually not cured; therefore. Just about any
solvent will remove It. In addition, a whole range
of other processes are available. Alternatives in-
clude 1,1,1 -trlchloroethane. which will be banned
for Its contribution to ozone depletion in a few
years; high pressure water; sodium bicarbonate;
strippable or peelable  coatings, which are best
used in operations  that don't have a huge paint
buildup; and various physical methods, such as
chiseling  the paint off.  Some firms recover
methylene chloride In paint booths; however, it is
an expensive  process that usually results in a
contaminated product.
   Gun and line cleaning can be performed with
other chemical strippers or firms can use a gun-
cleaning station, which  Is a 55-gallon drum with
a fitting on top for the gun. Instead of spraying the
solvent into the atmosphere, you put the gun into
the fitting, shoot It, and collect the solvent for
   For immersion  stripping, emissions can  be
better contained by using a water blanket and by
covering the vat when It's not in use. Alternatively,
firms can use on-site  distillation  or  send the
material to be cleaned  off-site. Other processes
include alkaline acid strippers, a cryogenic tech-
nique, and blasting with wheat starch are also
options. Firms can also avoid painting altogether;
however, it may be more economical to paint and
strip In one place, and customers may prefer the
painted merchandise.
   By the year 2000, use  of methylene chloride
by original equipment manufacturers  will have
been reduced to nearly one-eighth of today's level.
   In the maintenance stripping sector, there are
many alternatives to using methylene chloride.
   •  Dry abrasives Include plastic media and
      wheat starch; wet abrasives use sodium
      bicarbonate, high  pressure water, and
      various fracture technologies;

   •  A whole  range of techniques work  on
      spectroscopy: laser, flash lamp, and

   •  A  biodegradation  technique  uses
      microorganisms and  takes approximately
      four or five weeks;

   •  American Airlines has chosen not to paint
      aircraft—they put on decals and keep their
      aircraft polished; and

   •  Finally, there are evaporation retardants.
      which,  when  added  to methylene
      chloride-based strippers, lower both the
      amount of stripper used for the Job and

   In the year 2000. methylene chloride will be
used  in maintenance stripping only about one-
fourth as much as it is currently. In the consumer
sector, two-thirds of the methylene chloride sold
is used in household stripping and one-third In
professional refinlshlng. primarily for wood-based
products although metal and plastic Items are also
stripped. A  variety of alternative chemicals are
available, some with flash points in the flammable
range, others In the combustible range.  Vapor
recovery for contract stripping  and evaporation
retardants may be viable for this market. The
combination of the OSHA PEL (permissible  ex-
posure level) and control technology that may be
required will be difficult for many businesses to
meet and may discourage future use of methylene
   Flammable alternatives are low molecular
weight hydrocarbons with flash points in the flam-
mable range and include things like acetone and
mineral spirits. Most of these substances  do not
strip cured paint well by themselves, and all of
them  pose a workplace danger because they  are
flammable. Also, they are photochemically reactive
and generally heavily regulated by EPA in the local
air districts. Many have  unscrutlnized chronic
health effects; mineral spirits, for Instance, have
never been tested for chronic toxiclty.
   There are a whole range of hydrocarbon sol-
vents with flash points in the combustible range.
These are  simply higher molecular weight
materials made of carbon, hydrogen, nitrogen, and
oxygen. We've heard a lot about dibasic  esters,
N-methyl pyrrolidone, and alkyl acetates. These
materials are not nearly as volatile as either  the

                                                                      Reducing Risk In Paint Stripping
flammable or chlorinated solvents and  don't
evaporate readily. They remain on the surface
much longer and therefore require a longer strip-
ping time.
    Hydrocarbon solvents are not exempt from
either Clean Air Act or local air district regulations,
so they are, by definition, VOCs. They contribute
to photochemical smog, even though the evapora-
tion rate is lower than for methylene  chloride.
Many have unscrutlnized chronic health effects.
Data on these solvents should be collected and
evaluated by the proper government agencies in
the next few years.
    Some thoughts on the other processes:

    •  Plastic media blasting is widely used in the
      maintenance sector. Substrate damage may
      occur with this particular technology, and
      many commercial airlines have  been
      reluctant to adopt it. In addition, use of
      plastic media produces a large volume of
      waste that, if it contains  chromium, is
      considered hazardous. When using plastic
      media in a hangar, firms  must prevent
      worker exposure to the dust generated in
      the stripping  process. Since dust control
      can  be  expensive, media blasting can
      require  an  extremely  high  capital

    •  Sodium bicarbonate is a  wet,  abrasive
      technique  that's very effective.  Since
      corrosion might occur if it is used to strip
      whole air frames, firms generally are using
      this  technique on panels, which  are then
      neutralized with an acid rinse. This method
      generates a liquid waste stream that must
      be put  through a wastewater treatment

    •  With carbon  dioxide  blasting, carbon
      dioxide  can add to the  global  warming
      problem. However, there is no net addition
      of carbon dioxide from this paint  stripping
      method  because the carbon dioxide was
      taken from other processes that would have
      emitted it. Nevertheless. California's
      Southcoast  Air Quality  Management
      District always  regulates  sources in its
      jurisdiction, so there may be future rulings
      on the carbon dioxide technique.

    •  Laser, flash lamp, and infrared technology
      may result in decomposition products from
      the  paint  that are dangerous.  These
      methods can make chrome airborne and
      convert polyurethanes  into cyanides,  for

    I'd like to talk briefly about how the regulatory
process has worked over  the last 15 years. A
chemical is used for a  number of years, then
evidence starts emerging that it might pose health
and environmental effects of various kinds, so it is
designated an evil chemical. Sometimes limited
action is taken, and later stronger action, either a
ban or environmental controls that are designed
to reduce or eliminate the use of the chemical.
    Now, what's  wrong with this process? One
problem is that government offices, even within the
same agency and certainly among different
governmental agencies,  have  different agendas;
nobody is taking an integrated look at the problem.
For example, the global change office at EPA will
be banning depleting substances over the next
decade. However, EPA  is practically marketing
photochemically reactive substances; they're en-
couraging  people  to move out of  the  ozone-
depleters into the smog-producing chemicals.
    On the other hand, the Southcoast Air Quality
Management District has put such stringent
regulations on smog-producing chemicals that, in
effect,  they've moved everybody  into the ozone
depleters. So  we have this tension between dif-
ferent government agencies. Also, nobody wants
chemicals to go in the air, neither the Southcoast
Air  Management District nor the ozone depletion
people, so they encourage cleaning solutions that
will shove the whole problem into the sewer. A
different office, the Office of Water at EPA. would
be concerned about these releases. Nobody seems
to have overall responsibility.  Rarely are govern-
ment people familiar with the actual processes.
They will discourage the use of particular chemi-
cals but not be aware of what processes people are
adopting and what chemicals they're using  in-
    I would like to commend  the Office of Toxic
Substances at EPA for  holding this conference
because it is useful to have a  dialogue back and
forth between the Agency and industry. The Office
of Toxic Substances is positioned perfectly in EPA.
It doesn't have responsibility  for any particular
medium nor  does it ban any particular set of
substances that contribute to a particular prob-
lem. So it is  most likely to take this integrated
    These various offices  at  EPA or other
governmental agencies pick out a chemical that
they dislike and ban It. Unfortunately, they don't
know about the alternatives, which are not ade-
quately scrutinized by the time they are marketed.

Many of the paint stripping alternatives being
proposed have not been adequately scrutinized for
their  health and environmental effects. There
simply is no systems approach to regulation, and
this encourages the use of dangerous processes
and alternatives.
    So what does this mean for paint stripping, in
particular? Because the regulations on methylene
chloride are extremely severe, many users will
simply stop using  It. We hear a lot about  how
nothing else can perform as well. It doesn't matter.
Once something goes on these lists and the regula-
tions become stronger, people won't continue to
use it. It simply is not cost effective to do so, no
matter how technically desirable the substance.
Users will adopt alternatives, and at the moment,
these substances are more or less unrestricted.
    What  can we do about this? We have to get
back in gear and agree that our aim is not to ban
ozone-depleting substances  or  get  rid of one
chemical but to better protect human health and
the environment overall. The regulators should
ask themselves if the current regime In place and
pending on methylene chloride is what they want.
And, at  that time, they should be  aware  that
methylene chloride use will decrease significantly
over the next several years and use of may alter-
natives will Increase. If this Is not the desired path,
then rethink the regulations and  make them less
stringent because almost certainly what's In place
will move people toward the alternatives.
    If it is the desired path, we need to look at all
the alternatives, to scrutinize their  health and
environmental effects as rapidly as possible. If we
identify severe problems, we have to  restrict the
alternatives as we have methylene chloride and
prevent their use in the marketplace.

Closing  Summary
Mary Ellen Weber
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C.
       Before I summarize, I would like to publicly
       recognize people from the Office of Toxic
       Substances who have worked  long and
hard on this conference. It Is the first conference
that we at EPA have ever put on, and I would like
to acknowledge Llbby Parker, Dan Axelrad, Susan
Krueger, and Bob Lee. I'm  also grateful  to our
contractors. JT&A, Inc.. and Abt Associates.
    The  Office of Toxic Substances Is anxious to
start EPA's next 20 years In a new vein. We are
painfully aware that there has been a separation
of activities between the various offices at EPA, and
the sort of "it's not in my territory" kind of men-
tality. That has been  a  result of the existing
statutes under which we operate and not because
people fail to recognize the Implications of what
they do.
    TSCA is uniquely positioned, however, to deal
in a multi-media fashion to try to help EPA's other
offices coordinate their activities. We already have
a number of interoffice task forces on clusters of
chemicals or industries as a whole. That is going
to be the way of the future, to  try to look at an
entire package of problems, a whole Industry, and
examine it from a multi-media standpoint—air,
water, solid waste.
    Some of the new code words we're using—like
life cycle—may sound like jargon, but they are
deeply  part of the actions, practices, and
philosophies at EPA. We are committed to looking
at the product from the point of view of production
use and disposition. And our method is not going
to be nearly so much focused on traditional com-
mand and control regulations, which ultimately in
its extreme is the "ban approach" to things, but
rather on trying to work on Information exchange
and technology transfer. We want to be a center
that provides new information on technologies and
methods that are available or emerging, and per-
haps to even force some technology in approaching
risk reduction, hopefully from a more voluntary,
cooperative standpoint.
   A number of programs are underway that we
think are going to make it much more financially
attractive for producers and users of chemicals to
use and distribute substances in an environmen-
tally responsible way—and to take that stance as
a marketing approach. Companies are finding en-
vironmentalism sells. Also,  companies are dis-
covering that if they  capture wastes instead of
discarding them, they are recapturing products
and saving money.
   We recognize that there are some trade-offs in
the new paint stripping methods. You put a lid on
the vat to stop vaporization, but then you've got to
dispose of a lot more of the product. In the past,
we've failed to consider the potential dangers of
alternatives  when we've looked at banning or
regulating substances, their use,  production, or
distribution. Unfortunately, we also have limited
resources—and that's where you all come in. We
need your help. We need information and test data.
We will be happy to give you our data, and we are
trying much harder to be sure that when we try to
contain a problem here, we don't cause a problem
   The accomplishments of this conference are
numerous. One of our original goals was to foster
a  spirit of what we're now calling "product
stewardship." It means having the producers (par-
ticularly) but also the users take responsibility for
informing the public about the safe uses of their
   Another goal of the conference was to increase
international understanding. It is clear that there
will probably always be certain difficulties because
of differences in cultures, philosophies in risk, and
scientific disagreements. But we must recognize
those differences and make them explicit. I think
we have accomplished that, but even more impor-

tantly, we have made it possible for some of our
international guests to exchange Information with
each other and with us on where they're going and
where they've been. If we're looking for alternatives
and substitutes for chemicals, we need test infor-
mation, and the United States no longer has the
resources or the ability to do all of the testing for
everybody everywhere.
   Another thing I've heard is that industry has
enjoyed the opportunity to talk face-to-face with
those of us who are regulators. We are delighted
with this opportunity to network, and there have
been some surprises. The big surprise for me was
discovering that there has been networking not
only within government agencies at this con-
ference but also within individual companies that
would not have happened had this conference not
taken place.
    The conference has made much more explicit
the understanding  that  any time  you want to
mitigate a risk, you must deal with the trade-ofis.
We cannot look at solutions to health and environ-
mental problems in isolation because there are
ripple effects. We need to look at the safety and
efficacy of substitutes when suggesting them as
alternatives to our current practices. And we've
had a chance to look at a multi-media approach to
risk reduction in paint stripping.
    We're very grateful to all of you for coming, and
I hope that our paths cross again.

Attendees List

                         INTERNATIONAL  CONFERENCE

                            ON  REDUCING   RISK  IN

                                  PAINT  STRIPPING

                                        Presented by the
                       U.S. Environmental Protection Agency

     February 12-13,  1991  •  Omni Shoreham Hotel  •  Washington, D.C.

                               ATTENDEES LIST
Abbott, Kenneth
Stripping Technologies, Inc.
2725 Ginter Road
Tucson, AZ 85706

Albright, David
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-794)
401 M Street, S.W.
Washington, DC 20460
(202) 245-4028

Algaler, Mark
Hillyard Chemical Company
302 North 4th Street
St. Joseph, MO 64502

Arle, Paul  G.
Church & Dwlght Company
3121 County Knoll
St. Charles, MO 63303

Arndt, Steve
Amdt Brothers Industries
695 West Avenue
Milford, CT 06460
(203) 876-8065

Auer, Charles
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-778)
401 M Street S.W.
Washington, DC 20460
(202) 382-3442

Austln-Crumpton, Susan
Besway Systems, Inc.
P.O. Box 682
Madison, TN 37115
Axelrad, Dan
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3686

Balrd, Ed
Wilson Imperial
115 Chestnut Street
Newark, NJ  07105
(201) 589-6050

Bander, Andrea
The Valspar Corporation
2841 South Ashland Avenue
Chicago, IL  60608

Bauer*, J.J.
Bell Helicopter
P.O. Box482, Dept.8E
Ft. Worth, TX 76101

Bennett, Jim
United Technologies, Inc.
P.O. Box 1900
Huntsville.AL 35807

Bhanot, Sanjay
Cleveland State University
6154 Park Ridge Drive
North Olmsted, OH 44070

Blxenman, Gerald L.
Bix Manufacturing Company, Inc.
Ashland City Highway Box 69
Ashland City, TN 37015
(800) 447-0070
Blxenman, Benny
Benco Sales, Inc.
P.O. Box 1215
Crossville, TN 38557

Blumke, Jill
Warren, Ml 48397-5000
(313) 574-8834

Bock, Gordon
The Old-House Journal
435 Ninth Street
Brooklyn, NY 11215

Boomis, James A.
NLB Corporation
29830 Back Road
Wixom, Ml 48096
(313) 624-5555

Boubel, Richard
Office of Deputy Secretary of Defense
201 North Washington Street
Alexandria, VA 22314
(703) 325-2211

Bowers-Irons, Gall
Technical Research Associates
410 Chlpeta Way, Suite 222
Salt Lake City, UT 84108-1209
(801) 582-8080

Boyer, David W.
ProSoCo, Inc.
755 Minnesota Avenue
P.O. Box 171677
Kansas City, KS 66101
(913) 281-2700

* registered, but did nor. attend.

Brown, Calvin
Norfolk Aviation Depot
Code 93600
Materials Engineering
Norfolk, VA 23511-5899
(804) 444-8297

Brown, Mike
Key Houston
13911 Atlantic Blvd.
Jacksonville, PL 32225

Burchlll, Michael
Atochem Space North America
620 Olde Yorke Road
Somerville, NJ  08876
(201) 704-2321

Burckle, John
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati, OH  45220
(513) 569-7506

Burinsky, Frank C.
NALCO Chemical
50 West Big Beaver Road
Suite 400
Troy, Ml 48084
(800) 233-7539

Burr, Gerald
230 Park Avenue South
New York. NY 10003

Callans, Dave
Turco Products/Division of Atochem
   North America
P.O. Box 195
Marion, OH 43302

Cammer, Paul
Halogenated Solvents Industry Alliance
1225 19th Street, N.W.
Suite 300
Washington, DC 20036-2411
(202) 223-5890

Campanella, Paul
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-794)
401 M Street S.W.
Washington, DC 20460
(202) 382-3945

Cantor,  Doreen
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-794)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3777
Carbone, Carmine
Northwest Airlines
Dept. C-8872
Minneapolis - St. Paul International
St. Paul, MN  55111

Carries, Robert
Striptech International
P.O. Box1875
Mount Pleasant, SC  29465

Carra, Joseph
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3686

Cates,  Michael
Maxwell  Labs
8888 Balboa Avenue
San Diego, CA  92133

Cavanagh, Colleen
Abt Associates
4800 Montgomery Lane
Suite 500
Bethesda, MD 20814

Cederberg, Inger
National Chemicals Inspectorate
P.O. Box 1384
S-171 27 Solna, Sweden
(46/8) 730-6794

Chen, Charles
Galaxy Scientific Corporation
71 Cantilllon Blvd.
Suite 100
Mays Landing, NJ 08330
(609) 625-0200

Chen, Chla
U.S. Occupational Health and Safety
Health Standards Division
U.S. Department of Labor
200 Constitution Ave., N.W.,
   Washington DC

Cheppe, Eli
Church & Dwight Company
469 North Harrison Street
Princeton, NJ 08543
(609) 683-5900

Chevallier, Marie Pierre
Atochem SA
4 Cours Michelet
Le Defense / CO Cedex 42
929 091  Paris
Le Defense France
(33/14) 900-8080
Clarke, Garth
Pittsburgh, PA 15235
(412) 256-2735

Clarkson, Michael J.
Henkel Chemicals Ltd.
292-308 Southbury Road, Enfleld
London, England EN1 1TS
(44/81) 443-2777

Colbert, Ken
Church & Dwight Company
469 North Harrison Street
Princeton, NJ 08543
(609) 497-7158

Contl, Mike
Abt Associates
4800 Montgomery Lane, Suite 500
Bethesda, MD 20814
(301) 913-0500

Cortina, Tom
Halogenated Solvents Industry Alliance
1225 19th Street, N.W.
Suite 300
Washington, DC 20036-2411
(202) 223-5890

Cozljnsen, Ron
Purac Incorporated
1845 East Band Road
Arlington Heights, IL 60004

Crutcher, Larry
E.I. duPont de Nemours & Company
Chestnut Run Plaza HR1091
P.O. Box 80
Wilmington, DE 19880
(302) 999-4841

Darr, D.E.
Union Carbide Chemicals and Plastics
   Company, Inc.
P.O. Box 8361, Building 740-5109
South Charleston, WV 25303
(304) 747-3649

Davis, Jack
General Motors
Truck & Bus Division
Flint, Ml 48551
(313) 236-5565

deArras, P.
Cl de la Croix Blanche Est
3, Rue Clement Ader
Fleury Merogis
91700 Salnte Genevieve
Des Bois, France

De Haye, Don
Turco Products/Division of Atochem
   North America
P.O. Box 195
Marion, OH 43302
(614) 382-5172

Deel, Omar
Battelle Columbus
505 King Avenue
Columbus, OH 43201-2693
(614) 424-4405

Dehls, Allan W.
Wilson-Imperial Company
115 Chestnut Street
Newark, NJ  07105
(201) 589-6050

DeMartlno, Tony
The Softness Group
250 Park Avenue South
New York, NY 10003
(212) 674-7600

Desmarlas, Leon
Spray-Strip,  Inc.
1307 Central Court
Hermitage, TN 37076
(800) 421-9498
(615) 883-5707

Dletrichson, Eva
National Chemicals Inspectorate
P.O. Box 1384
S-171 27 Solna, Sweden
(46/8) 730-6802

Dlstaso, John
Turco Products/Division of Atochem
   North America
P.O. Box 195
Marion, OH  43302

Dotson, Richard A.
Aero-Blast Products, Inc.
630 East Bronson Street
South Bend, IN  46618
(219) 288-0461

Drust, Bert E.
Aero-Blast Products, Inc.
630 East Bronson Street
South Bend, IN  46618

Dugard, Paul
ICI Americas, Inc.
General Chemicals • Tatnall 2
Wilmington,  DE 19897
(302) 886-4844

Durante, Anthony
GAP Chemicals Corporation
1361 Alps Road, Bldg. 8, Floor 2
Wayne, NJ 07470
(201) 628-3891

Eaken, Bill
R.W. Eaken, Inc.
P.O. Box 171
Leesport, PA 19533
(215) 926-2136
Eberle, Sandra
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 532
Bethesda, MO 20816
(301) 492-6550

Etheridge, Oscar
U.S. Coast Guard
Aircraft Repair and Supply Center
Elizabeth City, NC 27909-5001

Evans, Reuben V.
Headquarters - U.S. Air Force Reserve
Portland, OR 97218-2797
(503) 335-4573

Faghanl, Davood
GAF Chemicals Corporation
1361 Alps Road, Bldg. 8, Floor 2
Wayne, NJ 07470
(201) 628-3891

Fairfield, Cheryl
National Institute for Occupational
   Safety and Health
4676 Columbia Parkway
Mail Stop R5
Cincinnati, OH 45226

Flnberg, William S.
P.O. Box 254
Burke, VA 22009-0254
(703) 978-7202

Fisher, Linda
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-788)
401 M Street S.W.
Washington, DC 20460
(202) 382-2902

Flaherty, Ralph T.
BASF Corporation
100 Cherry Hill Road
Parsippany, NJ 07054

Flanagan, Ken
W.M. Barr & Company, Inc.
P.O. Box 1879
Memphis, TN  38101
(901)775-0100, Ext. 277

Fogerty, Kevin
Galaxy Scientific Corporation
71 Cantillion Blvd., Suite 100
Mays  Landing, NJ 08330
(609) 625-0200

Foley, Lester
Deane & Company
Point Claire, Quebec
    H9R1A8 Canada
(514) 697-3730

Fortin, Thaddeus
Haas Corporation
American and Cumberland Streets
Philadelphia, PA 19133

Fuslak, Frank
GAF Chemicals Corporation
1361 Alps Road
Wayne, NJ 07470
(201) 628-4123

Ghlo, John
W.M. Barr & Company, Inc.
P.O. Box 1879
Memphis, TN 38101
(901) 775-0100

Gideon, James
National Institute for Occupational
   Safety and Health
4676 Columbia Parkway
Mail Stop R5
Cincinnati, OH 45226

Gillen, Matthew
Occupational Health Foundation
112616th Street, N.W.
Washington, DC 20015
(202) 887-1980

Gillman, Hy
Arco Chemical Company
3801 West Chester Pike
Newtown Square, PA 19073

Girman, John
U.S. Environmental Protection Agency
401 M Street S.W.
Washington, DC 20460
(703) 308-8790

Grainger, John
Turco Products/Division of Atochem
   North America
7300 Bolsa Avenue
Westminster, CA 92684
(714) 892-7179

Grayson, Lisa
JT&A, Inc.
1000 Connecticut Avenue, N.W.
Suite 802
Washington, DC 20036
(202) 833-3380

Graves, Beverly A.
Gardner Publications/Products Finishing
6600 Clough Pike
Cincinnati, OH  45244-4090
(513) 231-8020

Greenwood, Mark
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-792)
401 M Street, S.W.
Washington, DC 20460
(202) 382-7505

Guillory, Anne
Norfolk Aviation Depot
Code 363
Materials Engineering
Norfolk, VA 23511-5899
(804) 444-8811

Gruber, John
Abt Associates
4800 Montgomery Lane
Suite 500
Bethesda, MD 20814
(301) 913-0500

Haag, Harold
Aqualon Company
P.O. Box15417
Wilmington, DE 19850-5417
(302) 995-3174

Haloftis, Alimene
U.S. Occupational Safety and Health
Office of Health Standards
U.S. Department of Labor
200 Constitution Avenue, N.W.
Room N-3718
Washington, DC  20210
(202) 523-7174

Handsy, Carl
Warren, Ml 48397-5000

Hanna, Fayez
U.S. Occupational Safety and Health
Office of Risk Reduction Technology
U.S. Department of Labor
200 Constitution Avenue, N.W.
Room N-3718
Washington, DC  20210
(202) 523-7174

Hansen, Jim
LC.P. Chemicals
Edison, NJ 08818
(201) 225-6600

Hassur, Steven
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC  20460
(202) 382-3686

Hayes, William
Dow Chemical
2020 Dow Center
Midland, Ml 48674
(517) 636-2664

Hayes, Arthur J.
Federal Aviation Administration
800 Independence Avenue, S.W.
Washington, DC  20591
(202) 267-9937
Head, James
Laser Technology, Inc.
10131 Colonial Industrial Drive
South Lyon, Ml 48178

Heastrup, Jed C.
Aerolyte Systems
1 Cable Car Drive
Washington, MO 63090
(314) 239-6721

Hershfield, David
U.S. Occupational Safety and Health
Office of Regulatory Impact Analysis
U.S. Department of Labor
200 Constitution Avenue, N.W.
Room N-3718
Washington, DC 20210
(202) 523-7174

Hickman, Janet
Dow Chemical
2020 Dow Center
Midland, Ml 48674

Higgins,  Bill
Cold Jet, Inc.
455 Wards Comer Road
Loveland, OH  45140

Miller, Tony
Turco Products/Division of Atochem
   North America
P.O. Box 195
Marion, OH 43302
(614) 382-5172

Hirsch, Al
Flow International
21440 68th Ave, South
Kent, WA 98032
(206) 872-4900, Ext 536

Holmes,  William
Health & Safety Executive
Magdalen House
Stanley Precinct
Bootle, Merseyside L20 307
United Kingdom
(44/51) 951-4791

Holzberg, Alvin (Al)
511 Gwynn Street
Babylon, NY  11702
(516) 661-4469

Honig, Steve
The Softness Group
250 Park Avenue South
New York, NY  10003
(212) 674-7600
Howanitz, Joseph
Fine Organlcs
205 Main Street
Lodl, NJ 07644
(201) 472-6800

Hussaln, Fayyaz
American Blorganlcs, Inc.
2236 Liberty Drive
Niagara Falls, NY 14304
(716) 283-1434

Hutson, vlcki
Abt Associates
4800 Montgomery Lane
Suite 500
Bethesda, MD 20814
(301) 913-0500

Ignasiak, Mike
Turco Products/Division of Atochem
   North America
P.O. Box 195
Marion, OH  43302
(614) 382-5172

Inman, Tim
Minuteman, Inc.
115 North Monroe
Waterloo, Wl 53594
(414) 478-2001

Jackson, Ronald
Aberdeen Proving Ground
Aberdeen, MD 21010-0541
(301) 671-2054

Jackson, Hal
DuPont Experimental Station
P.O. Box 80366
Wilmington, DE 19898-0366
(302) 695-3671

James, Roger
Royal Australian Air Force
Australian Embassy
1601 Massachusetts Avenue, N.W.
Washington, DC 20036
(202) 797-3048

James, Evangeline
Continental Airlines
7300 World Way West
Los Angeles, CA 90045
(213) 646-5847

Johnson, Todd  L
U.S. Army
Depot System Command
Chambersburg, PA 17201-4170
(717) 267-9427

Johnson, Steve
Creative Technologies
7 North Laurens Street
Greenville, SC 29601
(212) 674-7600

Johnson, P.G.
ICI PLC Chemicals & Polymers Limited
P.O. Box 19, Weston Point
Runcom, Cheshire WA7 4LW, United
(44/92) 851-4444

Jones, Thomas R.
Martin Marietta Hazwrap
RO. Box 2003, Mail Stop 7606
Oak Ridge, TN 37831-7606

Jones, Stephen R.
U.S. Occupational Safety and Health
Office of General Counsel
U.S. Department of Labor
Room S-4004
200 Constitution Avenue, N.W.
Washington, DC 20210

Keller, George
Continental Airlines
7300 World Way West
Los Angeles, CA 90045
(213) 646-5847

Kelly, Terry
Blu-Surf, Inc.
P.O. Box 190
Parma,  Ml 49269
(517) 531-3346

Klosowski, Mary A.
BASF Corporation
1609 Biddle Avenue
Wyandotte, Ml 48192

Konopka, Joe
U.S. Technology Corporation
1346 East Monroe
South Bend, IN 46615
(219) 287-4732

Kovach, J.  Louis
Nucon International
7000 Huntley Road
Columbus, OH 43229-1035
(614) 846-5710

Kremer,  Rod
Vulcan Chemicals
P.O. 80X530390
Birmingham, AL 35230-0390
(205) 877-3511

Krenson, John G.
Besway Systems, Inc.
P.O. Box 682
Madison, TN 37115

Krueger, Bruce
Alpheus Cleaning Technology
9105 Milliken Avenue
Rancho Cucamonga, CA 91730
Krueger, Susan
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3686

Kruger,  Ulrich
Lufthansa German Airlines
Weg belm Jager
D-2000 Hamburg 63, Germany
(49/40) 5070-3929

Kurita, Hiroshi
Japan Association for Hygiene of
   Chlorinated Solvents
Hongo - Wakai Bldg.
40-17, Hongo 2-Chome
Bunkyo - Ku
Tokyo 113, Japan
(81/03) 814-3411

Lahr, Steven
GAP Chemicals Corporation
1361 Alps Road, Bldg. 8, Floor 2
Wayne, NJ 07470
(201) 628-3891

Lande, Maurice
AKR Robotics
35367 Schoolcraft
Uvonla, Ml 48150
(313) 261-8700

Lee, L.W. Budd
Dow Chemical Company
1691 North Swede Road
Midland, Ml 48674
(517) 636-1415

Lee, Rick
Bob Schmidt, Inc.
6040 Osborn
Houston, TX  77033
(713) 644-2071

Lee II, Robert E.
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3686

Lenz, Ruben
Ogitvie Mills
1 Place Vllle-Marle
Montreal, Quebec H3B-2X2  Canada
(514) 866-7961

Lewis, Mike
Cold Jet, Inc.
455 Wards Comer Road
Loveland, OH 45140

Litton, Ronald K.
Eastman Chemical Products, Inc.
P.O. Box 431, Bldg. 230
Klngsport,TN 37662
(615) 229-6434

Long, George
Environmental Health Directorate
Department of National Health and
Room 233
Ottawa, Ontario K1AOL2 Canada
(613) 957-1883

Longanecker, Larry
U.S. Environmental Protection Agency
Office of Toxic Substances (TS-779)
401 M Street, S.W.
Washington, DC 20460
(202) 382-3686

Lopez, Carlos
3M Company
3M Center, Bldg. 251-1C-09
SL Paul, MN  55144-1000

Lovoi, Paul
International Technical Associates
2281  Calle de Luna
Santa Clara, CA 95054-1002
(408) 748-9955

Luckemeyer, Tom
Jet Edge,  Inc.
825 Rhode Island Avenue South
Minneapolis, MN 55426
(612) 545-1477

Lynn, Bill
Sponge-Jet, Inc.
10 Grove Street
Dover, NH 03820
(603) 742-8350

Madretzke, Hank
Unocal Chemical
100 Walnut Avenue
Clark, NJ  07066
(201) 574-9300

Mainz, Eric
Vulcan Chemicals
Research and Development
P.O. Box12283
Wichita, KS 67277
(316) 529-7536

Mathur,  Ashok N.
Air Products & Chemicals
733 West Broad Street
Emmaus, PA 18049

McDonald, Gene
Church & Dwight Company
469 North Harrison Street
Princeton, NJ 08543
(609) 683-5900

McGary, Fritz
Star Bronze Company
803 South Mahonlng Avenue
Alliance, OH 44601
(216) 823-1550

McGregor, Ian
Fielding Chemical* Umlted
3549 Mavis Road
Mlsslssauga, Ontario
   L5C1T7 Canada

McLean, Steve
The Savogran Company
259 Lenox Street
Norwood, MA 02062

Meade, Jeff
NALCO Chemical
50 West Big Beaver Road
Suite 400
Troy, Ml 46084
(600) 233-7539

Meuer, Gary
Air Force Materials Laboratory
Wright Research & Development Center
Dayton, OH 45433-6503
(513) 255-7463

Michael, Larry
The Boeing  Company
3801 South  Oliver, Mall Stop K76-67
Wichita, KS 67210
(316) 526-2338

Mickey, Sam
U.S. Coast Guard
Aircraft Repair and Supply Center
Elizabeth City, NC 27909-5001

Millar, Jamee T.
Naval Ordnance Station
Code 0922
Indian Head, MD 20640-5000
(301) 743-4402

Monlque,  Mark
The Savogran Company
259 Lenox Street
P.O. Box 130
Norwood, MA 02062

Mooy, Thomae
KLM Royal Dutch Airlines
Dept. 8PL/CF
P.O. Box 7700
(31/02) 0649-4244

Moran, John
Laborers International Union
905 16th Street, N.W.
Washington, DC 20006
(202) 628-5465
Morgenroth, Vic
Environment Directorate
Organization for Economic Cooperation
   and Development
2, rue Andre-Pascal
75016 Paris, France
(33/01) 4524-8200

Morton, Peter
Romlo Chemical Company
2081 Bay Road
East Palo Alto, CA 94303
(415) 324-1638

Mounte, Michael
Dow Chemical
2020 Dow Center
Midland, Ml 48674
(517) 636-1397

Muller, Mark
Galaxy Scientific Corporation
71 Cantllllon Blvd., Suite 100
Mays Landing, NJ 06330
(609) 025-0200

Nooney, Michelle
Sellg Chemical Industries
P.O. 80X43106
Atlanta, QA 30378

Noordermeer, H.C.L.
KLM Royal Dutch Airlines
Dept. SPL/CF
P.O. Box 7700
Schlphol-East 1117 ZL, The

Nudelman, Alan K.
Composition Materials Co., Inc.
1375 Kings Highway East
Falrfleld, CT 06430

O'Brien, John
Specialty Paint Products
1729 Northfleld Drive
Rochester Hills, Ml 48309
(313) 852-0541

O'Connor, John C.
Naval Avionics Center
6000 East 21st Street
Indianapolis, IN  46219-2189
(317) 363-7022

O'Sulllvan, Jr., Robert E.
E.I. duPont de Nemours & Company
712 Cheltenham Road
Wilmington, DE  19808
(302) 992-2771

Oeetrelch, John
OglMe Mills
1 Place Vllle-Marle
Montreal, Quebec
   H3B-2X2  Canada
(514) 866-7961
Ogden, John
General Motors
30400 Mound Road
Warren, Ml 48090-9015
(313) 947-1852

Oetrowekl, Phillip J.
Occidental Chemical Corporation
P.O. Box 344, Development Center V-81
Niagara Falls, NY  14302

Palmatary, Stacy L.
Ooddental Chemical Corporation
5005 LBJ Freeway
Dallas, TX 75380
(214) 404-3411

Parker, Jean E. (Ubby)
U.S. Environmental Protection Agency
Office of Toxic Substances (T8-779)
401 M Street, 8.W.
Washington, DC 20460
(202) 382-3686

Paul), Robert
Paul) & Griffin
907 Cottlng Lane
Vacavllle, CA 95688
(707) 447-7000

Pereniua, Lena
National Chemicals Inspectorate
P.O. Box 1384
8-171 27 Solna, Sweden
(46/8) 730-6386

Perry, Gregory
BASF Corporation
100 Cherry Hill Road
Parsfppany, NJ 07054
(201) 316-3978

Platklewlcz, W.
ICI Chemicals and Polymers
P.O. Box 13
Runcom, Cheshire WA7-4QF, United

Plumley, Wally J.
Lockheed Aeronautical Systems
86 South Cobb Drive
Marietta, QA 30063
(404) 494-5706

Powell, Charles W.
United Technologies, Inc.
P.O. Box 1900
Huntsvllle.AL  35807
(205) 721-2777

Prltz, Karen W.
BASF Corporation
100 Cherry Hill Road
Parslppany, NJ 07054

Prothero, Scott
U.S. Environmental Protection Agency
Office of Toxic Substancee (T8-779)
401 M Street, 8.W.
Washington, DC 20460
(202) 252-0981

Raber, James A.
Star Bronze Company
803 South Mahonlng Avenue
Alliance, OH 44601
(216) 823-1550

Ray, Robert A.
Thompson & Formby, Inc.
P.O. Box 667
Olive Branch, MS 38654
(601) 895-5572, Ext. 232

Readahaw, R.L.
Union Carbide Chemicals and Plastics
   Company, Inc.
P.O. Box 8361, Building 740-5109
South Charleston, WV 25303

Reed,  Dennis
U.S. Army
K Army Depot
Attn: 8D8LE • MME
Chambersburg, PA 17201

Relnecke*, Werner
Qg. Scheldel GmbH
jahnstr. 38-42
W-8606 Hlrschald, Germany
(49/95) 434-971

Richmond, A.V.
W.M. Barr & Company, Inc.
P.O. Box 1879
Memphis, TN 38101

Risotto,  Steve
Halogenated Solvents Industry Alliance
1225 19th Street, N.W.
Suite 300
Washington, DC 20036-2411
(202) 223-5690

Roney, Connie
IMP Group Limited Aerospace Division
2651  Dutch Village Road
Suite 400
Halifax,  Nova Scotia
   B3M3N6 Canada
(902) 873-2250, Ext 467

Rossnsteel, Robert
U.S. Environmental Protection Agency
Office of Air Quality Planning and
   Standards (8TD-1041)
Research Triangle Park, NC 27711
Roeel, Qeorge
McDonnell Douglas
P.O. Box 516
St. Louis, MO 63166
(405) 737-3182

Ruahlng, J. Carroll
EZE Products
P.O. Box 6744
Greenville, 8C 29606

Rushing, J. Mitchell
EZE Products
P.O. Box 5744
Greenville, 8C 29606
(803) 879-7100

Ryan, Glenn
General Motors
GM Technical Center
30300 Mound Road
Warren, Ml 48090-9040

Sanders*, Wlllard
Textron Aerostructurea Division
P.O. Box 210
Nashville, TN 37202

Sauls, Johnny
U.S. Coast Guard
Aircraft Repair and Supply Center
Elizabeth City, NC 27909-5001
(919) 335-6250

Schaeffer, Val
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 700
Bethesda, MD 20816
(301) 492-6994

Schapker*. Ken
Dubols Chemicals, Inc.
511 Walnut Street
Cincinnati, OH 45202
(513) 762-6901

Scharwat, Frank
WOMA Corporation
P.O. Box 6793
Edison, NJ 06818
(201) 417-0010

Schelhlng, Paul
U.S. Department of Energy
1000 Independence Avenue, 8.W.
Washington, DC  20585
(202) 586-7234

Schmltz, Wayne
McDonnell Douglas
2 Grlmsley Station
Bluffs Court
8t Louis, MO 63129
(314) 233-0003

Schoulal, Nicholas J.
Calllngton Haven Pty Ltd
2 Euston Street, Rydalmere
Sydney, Australia 2116

Schrelner, Jamea L.
Exxon Chemical Company
P.O. Box 5200
Baytown, TX 77522-5200

Sclarratta, Mark J.
Naval Ordinance Station
11 Thompson Lane
Indian Head, MD 20640
(301) 743-4658

Seemann, Henry
AKR Robotics
35367 Schoolcrast
Livonia, Ml 48150

Selfert, Harry
Haas Corporation
American and Cumberland Streets
Philadelphia, PA 19133
(215) 425-4000

Sharlsse, Karan
U.S. Air Force
The Pentagon
Washington, DC 20330
(703) 897-9297

Shaw, IJaz
National Solvent Corporation
955 West Smith Road
Medina, OH 44256
(216) 725-4991

Shehl, Jack
JASCO Chemical Corporation
P.O. Box J
Mountain View, CA 94042

Shim, Jae
U.S. Army
Picatlnny Arsenal, NJ 07806

Simpson, Qlenn
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 656
Bethesda, MD 20816
(301) 492-6962

Simpson, Charles E.
Boeing Company
P.O. Box 3707, M8 7E-ER
Seattle, WA 98124-2207

Smart, William D.
Ashland Chemical, Inc.
5200 Blazer Parkway
Dublin, OH 43017

Smith, Charles
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 532
Bethesda,MD 20816
(301) 492-6550

Smith, Gary
E.I. duPont de Nemours & Company
P.O. Box 80721
Wilmington, DE 19880-0721
(302) 999-5935

Smith, Willie R.
McGean-Rohco, Inc.
9520 East Ceebee Drive
Downey, CA 90241

Smock, Joseph B.
Wilson-Imperial Company
115 Chestnut Street
Newark, NJ 07105
(201) 589-6050

Soley, Paul
Ardrox, Inc.
16961  Knott Avenue
La Mirada, CA 90638
(714) 739-2821, Ext. 11

Spears, Jr., William  E.
CDS Group
503 McKeever, #1510
Arcola.TX 77583-9805

Stanley, Don
EZE Products
P.O. Box 5744
Greenville, SC 29606
(803) 879-7100

Stevens, William D.
Delta Airlines
TOC II — Department 226
Atlanta, GA 30320
(404) 765-3446

Stone, Anthony
United Technologies, Inc.
P.O. Box1900
Huntsville, AL 35807

Stratford, Scott
Alpheus Cleaning Technology
9105 Milliken Avenue
Rancho Cucamonga, CA 91730
(714) 944-0055
Sullivan, Carl J.
Arco Chemical Company
3801 West Chester Pike
Newt own Square, PA 19073

Sutterfleld, Judith
JT&A, Inc.
1000 Connecticut Avenue, N.W.
Suite 802
Washington, DC 20036
(202) 833-3380

Swartz, James
Northwest Airlines
5101 Northwest Drive
Dept. C4020
St. Paul, MN  55111-3034

Taggart, Judith
JT&A, Inc.
1000 Connecticut Avenue, N.W.
Suite 802
Washington, DC 20036
(202) 833-3380

Taylor, Diane
Embassy of Switzerland
2900 Cathedral  Avenue, N.W.
Washington, DC 20008
(202) 745-7905

Thompson, F. Gurney
E.I. duPont de Nemours & Company
P.O. Box 80723
Wilmington, DE 19880-0723
(302) 999-4008

Trippe, Tony
Maxwell Laboratories
8888 Balboa Avenue
San Diego, CA  92123

Trouba, David J.
JT&A, Inc.
1000 Connecticut Avenue, N.W.
Suite 802
Washington, DC 20036
(202) 833-3380

Van Alstyne, David
Polygon Industries
8 North Queen Street
Lancaster, PA 17603
(717) 399-9903

Verkerke, Peter
Brotherhood of Painters, AFL-CIO
1750 New York Avenue, N.W.
Washington, DC 20006
(202) 637-0738

Vico, Martin
Arco Chemical Company
3801 West Chester Pike
Newtown Square, PA 19073-2320
(215) 359-5725
Vlsalsouk, Sam
Ixtal Blast Technology Corporation
627 John Street
Victoria, British Columbia
   VST 1T8 Canada
(604) 386-4321

Vollmer, Gerald
Federal Ministry of the Environment
Bonn, Germany
(49/228) 305-2741

Wahlstrom,  Bo
National Chemicals Inspectorate
P.O. Box 1384
S-171 27 Solna, Sweden
(46/8) 730-6386

Walsh, William C.
BASF Corporation
100 Cherry Hill Road
Parsippany, NJ 07054

Warren, Jonathan
PPG Chemfll
1200 Piedmont
Troy, Ml 48083
(313) 689-0720, Ext. 151

Wesson, Ed
San Antonio Air Logistics Center
Kelly AFB.TX  78241-5000
(512) 925-8541

Way, Mike
Laser Technology, Inc.
10131 Colonial Industrial Drive
South Lyon, Ml 48178
(313) 437-7625

Weber, Mary Ellen
U.S. Environmental Protection Agency
Office of Toxic  Substances
401 M Street, S.W.
Washington, DC 20460
(202) 382-3667

White, Sharlot
Paint Remover Manufacturers
P.O. Box 859
Vlncennes, IN  47591
(812) 882-3987

White, David L
Kwlck Kleen Industrial Solvents
P.O. Box 807
Vlncennes, IN  47591
(812) 882-3987

Whitfleld, James A.
Naval Aviation Depot
Code 35420
Cherry Point, NC  28533

Whittaker, Christine
U S. Occupational Safety and Health
 ' Administration
Office of Risk Reduction Technology
Health Standards Division
U.S. Department of Labor
200 Constitution Avenue, N.W.
Washington, DC  20210
(202) 523-7174

Wilkinson, Keith
Aceto Corporation
One Hollow Lane
Lake Success, NY  11042

Wind, Marilyn
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 724
Directorate for Health Science
Bethesda, MD 20816
(301) 492-6447
Winebarger, Bobby
Norfolk Aviation Depot
Code 5400
Materials Engineering
Norfolk, VA 23511-5899
(804) 444-8574

Wolf, Katy
The Institute for Research & Technical
1429 South Bundy Drive
Los Angeles, CA 90025
(213) 826-4700

Wu, Peter
Boeing Commercial Airplane Group —
   Wichita Division
P.O. Box 7730, Mail Stop K-50-23
Wichita, KS 67277-7730
(316) 526-2351
Yaksick, Jr., George L
Brotherhood of Painters, AFL-CIO
1750 New York Avenue, N.W.
Washington, DC  20006
(202) 637-0700

Yoh III, Harold
(609) 467-5522

Zamula, William
U.S. Consumer Product Safety
5401 Westbard Avenue
Room 532
Bethesda, MD 20816
(301) 492-6550

Supplemental Information

This section contains reports not presented at the conference but submitted as
additional paint stripping information.
Turco Environmentally Acceptable Paint Stripper
Turco Products, Inc.

Armex Sodium Bicarbonate Blast Media Integrity on Aluminum Surfaces
J.H. Van Scriver Associates

Environmentally Acceptable Paint Removal Systems

Reducing Hazardous Risks of Chemical Stripping through Effective Waste Treatment
W.L Becktel

Plastic Media Blasting—The Wise Alternative to Chemical Stripping
Richard A. Dotson

Significant Factors of Media Selection for the Dry Stripping Process
Bob Ken

Non-methylene Chloride Paint Removers Based on /V-methyl-2-pyrrolidone (NMP) and Thickened
with Ethylhydroxyethylcellulose (EHEC)
Harold F. Haag

Solvent Recovery Using the Brayton Cycle Heat Pump
Paul E. Scheming

                       TURCO PRODUCTS, INC,
                          7300 BOLSA AVENUE
                      WESTMINSTER, CALIF. 92684-3600
                       TELEPHONE NO. 714/890-3600

      TURCO PRODUCTS, INC. • 7300 BOLSA AVENUE, WESTMINSTER, CALIFORNIA 92684-3600 • 714/890-3600
                         TURCO^E.  A. STRIPPER

TURCO E.A. STRIPPER is a thixotropic, light green liquid remover developed for stripping
resistant finishes such as epoxies, epoxy primers, polyurethanes, alkyds and similar cata-
lyzed paints.

TURCO E.A. STRIPPER paint remover offers a significant advance in improving work place
safety since it  does not generate obnoxious fumes or odors and is free from methylene chlo-
ride, chlorinated solvents, phenols, chromates, ammonia and amines.

TURCO E.A. STRIPPER  can be used on aluminum, mild steel, cast iron, and titanium when
used as directed. TURCO E.A. STRIPPER  is not recommended for use on high strength
steel and magnesium. TURCO E.A. STRIPPER meets the "Effect on Metals" requirements
of MIL-R-81903 A (AS).


TURCO E.A. STRIPPER offers these features:

1.  Flash point over 200°F, Pensky Martens.
2.  Used as received. No mixing or dilution required.
3.  Clings  to vertical and overhead surfaces.
4.  Free from obnoxious fumes and odors.
5.  Used at ambient temperature, above 60°F.
6.  395 gr/1 V.O.C. @ <2 mm Hg V.O.C. Vapor Pressure

Application: Apply a thick, uniform coating to surface being stripped by means of nonatom-
izing spray or by brushing. Allow sufficient time for stripper to work.  Agitation with a
stiff bristle brush will aid in removal of the finish.

Removal:  Rinse with high volume, high pressure water or squeegee off bulk of stripped
paint and TURCO E.A. STRIPPER, then remove residues with emulsion cleaner and/or
wipe solvent. (See TURCO 6709).


Dispose of spent remover and paint residue per local, state and regional regulations.  Refer
to your TURCO MATERIAL SAFETY DATA SHEET for additional disposal information.

TURCO E.A. STRIPPER contains formic acid. Avoid contact with eyes, skin and clothing.
Do not take internally.  Do not spray in confined areas.  Avoid prolonged breathing of
vapors. Use with adequate (equivalent to outdoor) ventilation.

Protective clothing, such as a chemical face shield or goggles and gloves should be worn
and a NIOSH-approved respirator equipped with a mechanical filter should be worn for
mist conditions.

Store containers at a temperature between 30°F and 120°F.

Before using this product refer to container label and TURCO MATERIAL SAFETY DATA
SHEET for additional precautionary, handling and first aid information.


The above information and recommendations concerning this product are based upon our
laboratory tests and field use experience.  However, since conditions of actual use are
beyond our control, any recommendations or suggestions are  made without warranty,
express or implied. Manufacturer's and seller's sole obligation shall be to replace  that
portion of the product shown to be defective.  Neither shall be liable for any loss, damage,
or injury, direct or consequential, arising out of the use of this product.
 Rev. 2/91(Sup. 1/91)

For over 60 years, Turco Products has been a leader in supplying formulated chemical
specialty products to industry. Over that time, Turco Products has acquired and
enjoyed a reputation as an innovator in the markets it serviced.  In the past, much of
the research effort expended by Turco Products was concentrated on enhancements of
performance, reductions of cost and general improvements in processing technologies.
In the more recent past, and especially in the last five to ten years, more and more of
that effort has been devoted to reducing or eliminating environmental and health con-
cerns involved with the use of some of these products, such as paint removing com-
pounds. This paper describes briefly one of the fruits of this research, a thickened
paint stripper for removing aircraft/aerospace coatings, such as polyurethanes and
epoxies. This new product contains no chlorinated solvents, no highly toxic organic
solvents, no phenols or cresols, no chrome compounds and no known carcinogens. It
is currently undergoing field test and is called Turco EA Stripper.

The environmental concerns alluded to above have resulted in increasingly stringent
regulations governing the use of chemicals known or expected to cause damage to the
environment or ecology.  These have taken the form of outright bans on certain chem-
icals in some locations, restrictions on VOC content, restrictions on vapor pressure,
restrictions on the weight of organic solvents that can be emmitted to the atmosphere,
restrictions on waste disposal, and other similar measures.  Responsible companies
support these as necessary to protect the one environment in which we all have to live.

In addition to environmental concerns, the last ten or fifteen years have seen the focus
of much attention on protection of the health of workers  and the community at large.
This has resulted in a  much greater awareness on the part of both affected groups to
the chemicals to which they are exposed. The "duty to inform" that has been imposed
on chemical companies by OSHA and numerous community Right to Know measures

has raised the consciousness of these groups, in particular with respect to known or
suspected carcinogens.  This has naturally led to pressure to remove these where possi-
ble. Again, responsible companies support these efforts to insure a safe work-place
both for their own workers and for those of the companies using these products.

Many of these concerns with regard to paint strippers have focused on methylene chlo-
ride.  Probably the most far-reaching of these questions relate to the possible carcino-
genicity of methylene chloride and to the disposal problems for waste containing very
low levels of methylene chloride.

In 1986, methylene chloride was added to the NTP list of chemicals that may reasonably
be expected to cause cancer in humans. This addition to the NTP list was based on
evidence that has been the subject of some debate as to its validity and relevance, but
the mere fact of its presence on the list made it necessary to show, on material safety
data sheets and labels for products containing methylene chloride, warnings that the
product contained a suspected carcinogen. This, of course, caused concern on the part
of many users of products containing methylene chloride.  Many user companies res-
ponded by restricting use of these products to designated areas  where vapor concentra-
tions could be more readily controlled, providing greater ventilation in those areas
where  methylene chloride is handled, providing  respiratory protective devices to workers,
or some combination of these three. Obviously a more suitable answer would be elimina-
tion of methylene chloride, and replacement with a less  toxic material.

Disposal of waste containing methylene chloride is increasingly difficult and expensive.
Very small amounts of methylene chloride may  contaminate very large amounts of rinse
water to the extent that the water must be treated to remove methylene chloride or
it must be disposed of as hazardous waste. These regulations are already expensive to

comply with and they can only be expected to be more stringent and expensive in the
future.   Here, too, the most suitable answer is to eliminate methylene chloride where-
ever possible and replace it with a less polluting alternative.

Turco Products has enjoyed a long history of innovative solutions to industry problems
in many areas, especially paint stripping. Some of the more noteworthy advances in
paint stripper technology introduced by Turco Products were the first use of methylene
chloride in paint strippers, development of the first truly effective epoxy and poly-
urethane strippers, the first effective use of phenol or cresol in paint and carbon removers,
the first effective use of evaporation retardants, the first acid-activated epoxy stripper,
and the first embrittlement-safe paint strippers, as well as a long and continuing list of
new approaches and new solutions to other difficult technical problems.

In other areas, responding to environmental and worker exposure concerns, Turco
Products has developed many products eliminating chrome compounds, others eliminat-
ing phenols and cresols, still other water-based products for use in replacing solvent
degreasers, hot tank strippers eliminating chlorinated solvents, phosphate-free cleaners,
and many others.  Until, now, however, there has been no satisfactory viscous, spray-on
stripper effective on resistant aircraft/aerospace  coatings.

Turco EA Stripper is designed to meet that need.  It is the first in a series of products
under development in a major research project.  These will be known as the "EA", or
Environmentally Acceptable, products and will feature products that had been tradi-
tionally based on chlorinated solvents, or other environmentally unacceptable compo-
nents.  These will include paint strippers, carbon removers, chem-mill maskants, coatings
and other  products, reformulated to eliminate those unacceptable ingredients.

Turco EA Stripper is a unique product, quite unlike previously available non-chlorinated
paint strippers.  It utilizes a novel approach to this problem, and is the subject of pend-
ing patent application.  It is slightly acid, viscous, pastel green liquid. Although all
chemicals, including water, have some degree of toxicity and can be hazardous if used
improperly, Turco EA Stripper contains only ingredients that are normally thought  of
as relatively non-hazardous.  It contains no known or suspected carcinogens. Although
slightly acid, the acid is present only as a dilute solution of a common organic  acid in
water.  It is not aggressive enough to constitute a corrosive hazard to skin, although,
of course, it is good practice, based on common sense, to avoid skin contact. The odor
is mild and generally considered not objectionable. The composite vapor pressure,
including the contributions of all organic material and water, is low, so vapor concen-
trations are low. It contains no so-called exempt solvents.

Turco EA Stripper strips most of the normally encountered aircraft and aerospace coat-
ings.  This includes epoxies, polyurethanes and the most difficult epoxy primers. The
appendix to this report shows performance data for Turco EA Stripper on several typi-
cal paint schedules. These were run by an independent testing lab.  As may be seen
from the data, stripping proceeds at an acceptable rate. Under normal conditions,
workers may continue  to work on the inside of the aircraft while stripping continues on
the outside. Depending on local regulations, waste EA Stripper may be disposed of as
combustible waste. If the acid is neutralized, none of the components has a RCRA
number and none is an EPA regulated waste.  Paint is generally stripped in  a manner
analogous to a methylene chloride based stripper, by blistering the paint and lifting it
from the surface in a bond release mechanism. Sometimes the degree of blistering or
the extent of swelling  is somewhat greater for paints stripped with Turco EA Stripper
than for those stripped with conventional methylene chloride based products.   Turco
EA Stripper will, because of its extremely low vapor pressure, stay wet and active  for

a considerably longer period of time than methylene chloride based strippers. This may
be of considerable advantage when the coating is very resistant and stripping times are
prolonged. This allows Turco EA Stripper to strip some resistant coatings in a single
application, while traditional strippers may require several, due to their tendency to
dry on prolonged standing.

Turco EA Stripper has several significant advantages over traditional methylene chlo-
ride and methylene chloride/phenol strippers. It is inherently a much safer product for
the worker to use. It inherently results in much reduced solvent emission and conse-
quent exposure for the community at large.  It is an effective,  versatile stripper. It
often may strip to bare metal in a single application, while traditional strippers may
require several applications and some hand work to achieve the same final degree of
stripping. Although it cannot be simply flushed down a drain and discharged to a POTW,
it requires much less onerous treatment and will not contaminate large volumes of
rinse water that must then be treated before disposal.

With these significant advantages, however, there are some limitations. Turco EA
Stripper is somewhat  more costly than traditional strippers.  This higher material cost,
however, is often balanced by lower overall operating costs. These lower overall costs
may be expected due  to lesser material consumption, lower treatment and disposal costs,
and the ability  to carry on other maintenance or overhaul operations while stripping is
in process. Stripping  times are also often somewhat longer, as might be expected.
This is undoubtedly due to the slower penetration time of alternate solvents compared
to methylene chloride, and is probably related to the greater molecular size of alternate
solvents.  This extra time requirement is most often in the neighborhood of 30  minutes
to 90 minutes, however, and may be of no real significance in the overall strip and
repaint schedule. At lower temperatures, however, this need for more time  becomes

greater and begins to be of much greater significance at temperatures less than about
60-65 °F.  At higher temperatures, however, the reverse is true and stripping becomes
feasible when traditional strippers become impractical due to excessive evaporation.
This becomes important at temperatures of 90 °F and above.  Finally, as with all acid
products, including aluminum brighteners, deoxidizers and conversion coatings, Turco
EA Stripper is corrosive to magnesium and will cause hydrogen embrittlement of high
strength steels. Assemblies containing these alloys will have to be masked off prior to
stripping operations.

Other alternatives to methylene chloride based strippers are currently under evaluation
in industry. These generally involve various forms of blasting.  The means generating
the most current interest are those using plastic media, carbon dioxide pellets, and high
pressure water blasting. These generally suffer from the same deficiencies. They tend
to be slow and labor intensive.  They may result in worker exposure to dust, both from
the blast media and the paint being removed.  Dust from strontium chromate or zinc
chromate primers would be of particular concern, since both are recognized human
carcinogens. Dust would also be of serious concern if it enters wing  fuels tanks, fuel
lines, hydraulic lines, etc. Finally,  damage to the substrate is a very real concern and
requires substantial engineering controls and quality assurance  monitoring to avoid this

With all of these concerns, however, some feel that this is a viable approach.  As an aid
to mechanical removal, especially with high pressure water blasting, Turco Products
offers a product similar to Turco EA Stripper that may be used to soften paint and thus
facilitate removal.  This is a neutral product, safe on magnesium  and high strength steel,
and is called Turco Paint Softener.  This method, softening the paint and stripping with
high pressure water, is the subject of considerable interest in Europe.

With the introduction of Turco EA Stripper, Turco Products continues its tradition of

offering innovative, cost-effective solutions to industry problems. Over the next

several years, Turco Products expects to expand and fill out its line of EA products and

fulfill its commitment to help provide a safe work place and a healthy environment for

all to enjoy.


                       TURCO EA STRIPPER
1.  Primer:  BMS 10-72 Ty VI
    Topcoat:  BMS 10-72 Ty VI

2.  Primer:  BMS 10-72 Ty VI
    Topcoat:  BMS 10-6O'Ty II

3.  Primer:  IS-F3-100
    Topcoat:  BMS 10-72 Ty VI

4.  Primer:  Mil-P-23377
    Topcoat:  Mil-C-83286

5.  Primer:  BMS 10-11 Ty I

6.  Primer:  BMS 10-20 Ty II
    Topcoat:  BMS 10-11 Ty  II

7.  Primer:  Mil-P-26915

8.  Primer:  BMS 10-72 Ty VI
    Topcoat:  BMS 10-72 Ty  VI

9.  Primer:  BMS 10-11 Ty  I Class  B
                                           Jj hour

                                           1 hour

                                           1'i hours

                                           1 hour

                                           I'i hours

                                           >i hour

                                           l?j hours

                                           1 hour

                                            1 hour

« — 5»0THU   15:12

                      REPLY TO P.O. BOX 141797
                     CORAL GABLES, FLORIDA 33114
                    OFFICE: 7010 S.W. 13TH STREET
                         MIAMI, FLORIDA 33144
                         PHONE (305) 767-5596
                         TELEX 4933347 SMI LH
                         FAX (305) -893-0431
  Turco Products,Inc.                            April 19.1990
  7300 Bolsa Avenue
  Westminster,  California 92684-3600              SMI/REF:  900361
                                               Page 3
                           Report of Test
                        TURCO EA STRIPPER
 Requested:   Test for conformance to M11-R-81903A (AS) Special Test,

                           Result of Test
 3.6  The panel after the rinse test  requires wiping with a  solvent
      before Kordpon system 1s applied.

 3.7  Test panels of aluminum QQ-A-250/5 painted to the requirements
      of Table  II using Desoto Super  Koropon Grey did strip  within 80
      to 90 minutes.  The control stripper did strip within 26 minutes.
 3.8  The residue 1s partially removed with water.  The pane! requires
      cleaning  or wiping with solvent before reflnlshlng.
                                            oseph Schruefervr.

                        REPLY TO P.O. BOX 141797
                      CORAL GABLES, FLORIDA 33114
                      OFFICE: 7019 S.W. 13TH STREET
                          MIAMI, FLORIDA 33144
                          PHONE (305) 757-5596
                          TELEX 4933347 SMI Ul
                           FAX (305) - 893-0431
Turco  Products,Inc.
7300 Bolsa Avenue
Westminster,California 92684-3600
April  25,1990
SMI/REF: 900361
                           TURCO EA STRIPPER
M11-R-25134B Lacquer Panel  A
M11-R-25134B Lacquer Panel  B
M11-R-25134B Enamel Panel  C
M11-R-81294C Epoxypolamide
MH-R-81294C Polyurethane
  approximate stripping  time
     30 min.
     30 min.
     35 min.
     55 min.
     65 min.
Tests are  spot tests using the procedure stated  in Mil-R-81903A, paragraph
4.5.5. Times are approximate on uncertified panels.
                                                 Respectful ly  submi tted,
                                                  Joseph Schruefer.Jr.

Materials and
      DATE:   April  30, 1990
                                                 PREPARED FOR:

                                                 Church & Dwight Company,  Inc.
                                                 Princeton, N.  J.
                                                 PREPARED BY:

                                                 J.  H. Van Solver Associates
                                                   n n« Vn^ACl/'tx.i
                                                     H. Van Sclver, P.E.
          J. H. Van Sciver Associates • 29 Vinton Road • Madison, New Jersey 07940 • (201) 377-1626


  In  early  1989,  test  data  on  the  integrity  of  aluminum
surfaces  in sodium  bicarbonate solutions  was developed.
This  work was  presented  at  the DOD Advanced  Coating
Removal Conference  in  April 1989.   Three  types  of  testing
were  utilized:   electrochemical corrosion testing, immersion
testing as  per ASTM F-483 and  sandwich  testing  as  per SAE
Aerospace Recommended  Practice 1512A.

Results of  this testing  showed sodium bicarbonate  to have
a low corrosion rate of  0.5 mpy (mils per year) at 120°F.
Good  correlation was obtained  between the three test
methods.  For  comparison, phosphoric acid, sodium  carbonate,
acetic acid and sodium chloride solutions were  immersion
tested.   All had higher  rates  than sodium bicarbonate.  The
buffering capacity  of  sodium bicarbonate  was shown to be
large.  Although sodium  bicarbonate will  decompose a few
percent with time and  temperature,  sodium sesqulcarbonate is
formed which has  great pH buffering capacity.   Even a 50%
sodium bicarbonate/sodium carbonate mixture  had a  low rate
of 3  mpy.   Corrosion rates  by  polarization resistance are


Some  users  of  Armex sodium  bicarbonate  blast media have
observed  a  staining effect  on  test panels which is cosmet-
ically undesirable.  Recent work has been completed to
identify  an appropriate  inhibitor  to eliminate  this dis-
coloration, lower corrosion, and at the same time  greatly
reduce the  corrosion in  other  solutions including  sodium
carbonate.  This  inhibitor  system  has been Identified.

Six candidate  inhibitor  systems were investigated.  Various
combinations of silicates,  borates, nitrites and organic
Inhibitors  known  to inhibit  aluminum were tested at 120°F.
All six inhibitors  lowered  the  corrosion  rate of 1% and 10%
Armex with  Inhibitor G having  the  largest rate  reduction

Solid sodium bicarbonate at high temperatures will decompose
into sodium carbonate and carbon dioxide.  The six candidate
Inhibitor systems were tested in 1% and 10% sodium carbonate.
Again Inhibitor G exhibited an effective large rate reduction

Immersion and sandwich testing was conducted on inhibited
(Inhibitor G) sodium bicarbonate, inhibited sodium carbonate
and comparltlve solutions.  Immersion testing as per ASTM
P-483 at 160°P showed the two inhibited solutions to have
the lowest rates of all solutions tested; including tap
water and distilled water.  Phosphoric acid, Mil-R-81903
acid stripper and sodium chloride samples pitted severely.

Sandwich testing conducted as per ARP 1512 revealed no
corrosion or staining of the aluminum with inhibited sodium
bicarbonate or sodium carbonate.

Samples of aluminum 7075, 2024 and 7075 ALC were immersion
tested for one year at 120°P In 1% and 10/5 Armex.  Corrosion
rates were not measurable after this exposure.


This work has shown that an effective inhibitor system has
been identified for Armex blast media.  Electrochemical,
immersion and sandwich testing in inhibited solutions has
shown a 94# reduction of corrosion rates at 160°P and
no staining of aluminum 7075, 2024 and 7075 ALC.

Sodium carbonate is also effectively Inhibited with a rate
reduction of 99% and no staining of aluminum 7075, 2024
and 7075 ALC.

One year immersion samples at 120°P in Armex solutions had
negligible corrosion.

  30 -i
03 OK
0) *-°
                      Corrosion Rates
               by Polarization Resistance
                            Mils per Year
                         Aluminum 7075 - T6
Solution A:
Solution B:
Solution C
Solution D

Solution E:
                                     Solution F:
                                     Solution G;
                                     Solution H
 1.0% Sodium Bicarbonate
10.0% Sodium Bicarbonate
10.0% ARMEX* Blast Medi
 7.5% Sodium Bicarbonate
 3.1% Sodium Carbonate
 5.0% Sodium Bicarbonate
 6.2% Sodium Carbonate,
 1.0% Sodium Hydroxide
 5.0% Sodium Bicarbonate
 6.2% Sodium Carbonate
 2.5% Sodium Bicarbonate
 9.3% Sodium Carbonate
12.3% Sodium Carbonate
                                     Solution I:   2.0% Phosphoric Acid

  2 -
•«—• -i
03 1
                 Corrosion Inhibition
              1%ARMEX  Blast Media
                      Aluminum 7075 - J6
Solution A:
Solution B:
Solution C:
Solution D;
Solution E:
Solution F:
Solution G
Solution H:

Solution I:
1%ARMEX? + Inhibitor/
r/oARMEX* + Inhibitor E
1%ARMEX? + Inhibitor C
1%ARMEX^4- Inhibitor E
1%ARMEX®+ Inhibitor F
1%ARMEX®+ Inhibitor 0
Synthetic Tap Water -
ASTM D1193
Distilled Water

30 -i
                     Corrosion Rates
             by  Polarization Resistance
                           Mils per Year
                       Aluminum 7075 - T6
Solution A:
Solution B:
Solution C:
Solution D;

Solution E:
                                    Solution F:
                                    Solution G
                                    Solution H
 1.0% Sodium Bicarbonate
10,0% Sodium Bicarbonate
10.0% ARMEX* Blast Medi
 7.5% Sodium Bicarbonate
 3.1% Sodium Carbonate
 5.0% Sodium Bicarbonate
 6.2% Sodium Carbonate,
 1.0% Sodium Hydroxide
 5.0% Sodium Bicarbonate
 6.2% Sodium Carbonate
 2.5% Sodium Bicarbonate
 9.3% Sodium Carbonate
12.3% Sodium Carbonate
                             H   I   Solution I:   2.0% Phosphoric Acid

13 1
                 Corrosion Inhibition
              1%ARMEX   Blast Media
                      Aluminum 7075 - T6
Solution A:
Solution B:
Solution C:
Solution D:
Solution E:
Solution F:
Solution G
Solution H:

Solution I:
1% ARMEX* + Inhibitor A
1% ARMEX* + Inhibitor F
1% ARMEXK + Inhibitor C
1% ARMEX* + Inhibitor E
1?oARMEX"'+ Inhibitor F
1% ARMEX* + Inhibitor C
Synthetic Tap Water -
Distilled Water

           Corrosion Inhibition
        10% ARMEX® Blast Media
                Aluminum 7075 -T6
                           Solution A:
                           Solution B:
                           Solution C:
                           Solution D:
                        1.2 Solution E:
                           Solution F:
                           Solution G
                           Solution H:

                           Solution I:
10%ARMEX^+ Inhibitor
10% ARMEX®-f Inhibitor
10% ARMEX* + Inhibitor
10% ARMEX"L' + Inhibitor
10% ARMEX® + Inhibitor
10% ARMEX® + Inhibitor
Synthetic Tap Water -
ASTM D1193
Distilled Water

        Corrosion Inhibition
1% Na2CO3 (Sodium  Carbonate)
             Aluminum 7075 - T6
    334         49°C(120°F)
                    Test Discontinued -
Solution A:   1% Sodium Carbonate
Solution B:   1% Sodium Carbonate
            Inhibitor A
Solution C:   1% Sodium Carbonate
            Inhibitor B
Solution D:   1% Sodium Carbonate ,
            Inhibitor C
Solution E:   1% Sodium Carbonate -
            Inhibitor E
                     Developed Foam  Solution F:   1 % Sodium Carbonate
                     F  G  H   I
                                      Inhibitor F
                           Solution G:  1% Sodium Carbonate
                                      Inhibitor G
                           Solution H:  Synthetic Tap Water -
                                      ASTM D1193
                           Solution I:   Distilled Water

         Corrosion Inhibition
10% Na2CO3 (Sodium Carbonate)
    Aluminum 7075 - T6
                 Solution A:   10% Sodium Carbonate
                 Solution B:   10% Sodium Carbonate h
                             Inhibitor A
                 Solution C:   10% Sodium Carbonate -\-
                             Inhibitor B
                 Solution D:   10% Sodium Carbonate f-
                             Inhibitor C
                 Solution E:   10% Sodium Carbonate t-
  Test Discontinued -             Inhibitor E
   Developed Foam  Solution F:   10% Sodium Carbonate f
                             Inhibitor F
                 Solution G:   10% Sodium Carbonate +
                             Inhibitor G
P  p   p   H   I    Solution H:   Synthetic Tap Water -
                 Solution I:    Distilled Water

   67.4  57.3
 Immersion Test
Corrosion  Rates
   Aluminum 7075 - T6
 160°F  10 Day Exposure
                   Solution A:
                   Solution B:

                   Solution C:
                   Solution D:
                   Solution E:
                   Solution F:
                                       Solution G:
                                       Solution H:

                                       Solution I:
                                        Solution J
1% Phosphoric Acid
1%& 10% Sodium
Acid Stripper
2% Sodium Chloride
Alkaline Stripper
Synthetic Tap Wate,
Distilled Water
                                Blast Media
                              1%& 10% Sodium
                                Carbonate +
                                Inhibitor G
                              1%& 10%ARMEX
                                Blast Media +
                                Inhibitor G

16961 Knott Avenue
La Mirada, California 90638
(714) 739-2821
FAX (714) 670-6480
Ardrox  Inc.  has  been  actively  investigating  the possibility  of
providing some new  chemistry  to  solve  an old problem -  paint removal
from Military and Commercial aircraft exteriors.

Over the past few years,  major changes have taken place in the areas of
environmental and  personal health and  safety issues.   Although  the
conventional type  application  paint  removers have for many  years
provided a valuable  service to the Aerospace Industry,  new technology
is now being Investigated.

All application  paint  removers,  which  are widely  used  throughout  the
industry for  the removal  of  paint from  the  airframe,  basically  use
methylene chloride as their carrier solvent.  This is present at about
60-80%  of  the  formulation.   The  balance  of simple  paint removal
formulations is  made up of  methanol, surfactant, thickener, evaporation
retarders and corrosion inhibitors.   Most  of  the paint schemes used in
our  industry are  not   effectively  removed by this simple type  of
formulation.   For aircraft  use, more  powerful paint removers have been
formulated using phenol or an organic acid as the activator.   In some
products we see  both phenol and acid used jointly as the activator.   An
additional problem arises in the use of organic acids  in that there are
unfortunately,   no  Inhibitors  which  can  be incorporated  into  the
formulation to stop hydrogen embrittlement of high  tensile steels.

To further highlight the environmental  and health  and safety problems,
we must realize  that  in  using  application  paint removers  In  their
present form we  are evaporating large volumes of methylene chloride and
other solvents into  the  atmosphere.  Operators are also being exposed
to the  effects  of methylene  chloride,  phenol and  other  raw materials
previously mentioned as possible  ingredients  of  the paint  remover.
Furthermore,  large volumes of highly contaminated  rinse  water have to
be disposed of.   This not only greatly increases operational costs but
Is also an ongoing  responsibility for the generator of this hazardous
                  A Formula For Excellence

When  the  new legislation and restrictions  started to become  known,  the
immediate reaction  of  the Aerospace  Industry  was  to  move  away  from
chemicals.   Many forms of mechanical means of  paint removal have  been
presented and evaluated.   Plastic Media Blasting,  Solid Carbon Dioxide
Blasting,  Liquid Nitrogen Blasting, High Pressure Water Blasting, paint
removal with Lasers plus  a  wide  variety of blasting media, have  been
presented complete  with  engineering packages.    However,  to date  and
especially for civil aircraft paint removal, no  really viable  process
has  come   to   light.    Problems have arisen  regarding  airframe
manufacturer acceptance of  the blasting pressures and high impact of
solids  which relate to possible  damage  to the aircraft structure.  A
number of questions  have also been asked with regard to effective paint
removal;  i.e.  time  factors  involved  and surface  condition prior to

During  our own  Research and  Development meetings,  we felt  that there
was  a  need for  a range  of  chemical paint  removers,  which would
adequately  remove  paint  from  the  aircraft  surface,  not  affect   the
structural  integrity of the  aircraft and use only raw  materials which
were  more  environmentally acceptable than  methylene  chloride   and
phenol.   It was also recognized that the mechanical  systems  had been a
very  welcome  alternative  to hazardous  chemicals.   Therefore   new
chemistry in the form of a paint softener in conjunction with some form
of  mechanical  action  to  remove  the  softened paint would be an
acceptable  compromise.

At  Ardrox we set ourselves final  objectives on all  research programs.
Sometimes  these  objectives were such that they  could not be  reached at
the first attempt or over  a  short time period.   The  final criteria  for
this  particular project was  to formulate a  range of neutral alkaline
environmentally  acceptable  application  paint  softeners.    The
formulation should  be  classed as  non-flammable and  incorporate  raw
materials  enabling  rinse  waters  to be treated  with  simple  (low cost)
effluent  treatment  plants  producing water which could be recirculated
and reused  for rinsing.

Clearly this has been  a major task,  but after  some months  of intense
laboratory  work,  followed  by evaluations with all types of mechanical
removal systems, we  have reached  a  significant  stage  in our research
project.  While we have not reached our final objective or finished our
development  program, we have recently provided new chemical products
for  evaluation  at selected Aerospace  locations,  covering both
Commercial and Military aircraft.

From early results of the previously mentioned evaluations and our own
internal  data,  we believe we  are  well on the  way  to satisfying two
significant  objectives  that  we  and the  industry,  set  as acceptable
alternative paint removal procedures.   Our final objective is still to
produce  a neutral formulation that  performs  like conventional   (high
strength) paint removers,  containing  no hazardous environmentally
unacceptable raw materials.   This may  require a major Joint effort in
conjunction with the  paint  manufacturers  and even  a change  in
technology, involving both chemical removal and paint application.

Ardrox  Inc.   is  preparing  to  launch   a  series  of new products
incorporating  new  chemistry and paint removal  techniques.    As
previously mentioned  we  have two specific approaches  -  these being:

   - A  range  of application paint  softeners  which  when used  in
     conjunction with  mechanical  assistance would produce a  paint
     removal  system.    These products  are  neutral  formulations
     containing no  hazardous  ingredients.   Without  fracturing the
     painted surface, they actually  penetrate and swell  the coating,
     breaking the bond.   Mechanical  systems can  then be used for final
     removal.  The chemical softening improves  removal  rates and allows
     lower pressures  and/or soft media to be used.

   - An   acid  activated  environmentally  acceptable  paint
     remover/softener which is  sufficiently active by itself to  remove
     some  paint  schemes,  but  may  also be used as  a paint softener,
     again in  conjunction with mechanical assistance on more adherent

                      McGean-Rohco, Inc., Gee-Bee Division
                    9520 East CeeBee Drive, Downey CA  90241

                     W. L. Becktel, New Products Supervisor
Historically  methylene chloride  based paint  strippers  have  been  successfully
used by the aircraft industry to remove the increasingly difficult paint systems
that are  used on commercial and  military aircraft.  They have  been,  and still
are, the preferred  strippers from the standpoint  of ease of application, effec-
tiveness  and  safety to the  aircraft.  However, we  are  now at a time  when EPA
(Environmental  Protection Agency) regulations  on disposal of hazardous wastes
(which  includes methylene chloride  and  the other  activating  chemicals  used in
chemical stripping, as well as the resulting paint residues) have become a major
and costly consideration  for those doing aircraft stripping.

In the past it was  simply a matter of applying a stripper, allowing it to buckle
and loosen  the paint  and then flushing  the  paint residues and spent stripper
down the  drain with copious amounts  of water.  However,  these practices are no
longer  permitted  by EPA  and local  restrictions now in place  and,  by even more
severe  ones  to come.  As it  now stands those  that are  stripping aircraft with
methylene chloride type  strippers  must adhere to  the strict EPA  standards on
handling hazardous  chemical wastes.

The currently accepted practice for  handling these  hazardous wastes involves the
construction  of plastic  chutes under the aircraft  to catch  the paint residues
and spent stripper, which are squeegeed off rather than rinsed  off of the air-
craft.  These residues are then collected  and  placed  in EPA approved 55 gallon
drums  and hauled  away by a waste disposal contractor.   The  final rinse water
must also be collected,  recycled and/or  treated  for release  to the sewer.  All
of this adds  up to considerable  increases  in costs,  time  and labor.

In  order to  overcome resistance  to the  use  of chemical  strippers  because of
costly restrictions, an  on-site  waste treatment system  has  been developed and
manufactured  by  Technotreat Corporation  specifically for the  paint  stripping
industry.   The system is currently being marketed by  McGean-Rohco,  Inc. and
offer  the following advantages.

    1.  All paint sludge,  solvent, chemicals and rinse water can  be washed into  a
       sump and pumped to  the treatment unit.   Depending  upon  the volume of waste
       water,  an intermediate holding tank may  be  required.

    2.  Paint  sludge can be ground In  a communitor or grinder pump so  that it can
       be  pumped into the  treatment unit.

    3.  All of the waste is then treated to  remove phenol,  formic acid,  chromium,
       methylene chloride  and other hazardous  materials.

Reducing Hazardous Risks of Chemical Stripping
Through Effective Waste Treatment
   4. The  treated  water and sludge,  including the ground up  paint flakes,  are
      discharged  to an  auto  indexing filter.   The sludge  on  the  disposable
      filter  media  consists  of  non-hazardous  solids,  paint  chips,  insoluble
      metallic hydroxides, dirt and  grease.   The volume will be in the range of
      100-200  Ibs.  per  aircraft,  depending  upon  the weight  of  the  paint

   5. The  treated waste  water is  tested before discharge  and  will meet  EPA
      standards of less than 1 mg/1 phenol and chromium.

   6. Some operators recycle the  clean water.

This equipment  is  designed not only to be compatible with your preferred method
of paint  stripping,  but will allow the maintenance  crew to  use the most effec-
tive strippers  containing phenol and chromium.  It  is chemically easier,  more
effective  and cheaper  to  oxidize phenol and reduce chrome  in a  concentrated,
small volume.   The hazardous chemicals are isolated and contained.  They do not
contaminate  the entire plant treatment system.   The  process can  be fully auto-
matic to  eliminate the need  for chemically trained operators.

To comply with  current EPA regulations, the hazardous wastes must  be pretreated
before  being diluted with other  plant streams  flowing  to the main waste water
treatment system or  municipal  facility.  Aviation maintenance  waste waters often
contain phenols,  formic acid,  ammonia, chromium, solvents, detergents and heavy
metals.   Most of these must be removed or neutralized.  The on-site system does
this in a batch process so  that  the chemistry can be  controlled and accidental
discharges prevented.   Each batch is treated specifically for what it  contains
and  is tested  to  be pure  and safe  before  the  cleaned water is  discharged or

Method  of Treatment

o  Solvents  are removed by  air  sparging and then catalytically oxidized.  The
   principle solvent removed  is  methylene  chloride.   The oxidation products of
   methylene chloride  include hydrochloric acid, which  is neutralized by scrub-
   bing with alkaline  water.

o  Acid and bases  are neutralized to an  acceptable  pH range of between 6.5 and

o  Phenol,  formic acid and  other organics can  be  oxidized  by aeration and hy-
   drogen peroxide.

o  Chromium 6 is  reduced either during treatment of the phenol or  in a  separate
   step using sodium metabisulfite,  then  precipitated with lime.

Reducing Hazardous Risks of Chemical Stripping
Through Effecitve Waste Treatment
o  Heavy metals,  such  as cadmium, lead, copper and zinc  can  be  removed if they
   are present,  but additional steps may  have  to be added.  The  batch process
   allows for such variations in  composition.

o  The  treated  water  is  filtered to  remove the  hazardous  precipitate.   Any
   unusual quantities  or deviations  from standard procedures  must  be identified
   and specific  treatment designed into  the system.

o  Finally,  a  special filter  and carbon  adsorbent can  be used to  clarify the
   effluent  water,  remove  any color and  adsorb minute  traces  of  toxic  mate-
   rials.  Ordinarily, such treatment is not required,  but it provides ultimate
   assurance that no contaminants will remain in the industrial effluent

o  Some local regulations are so  stringent, the effluent water must be nearly as
   pure as drinking water.   In this situation, total recycle of the water is in-
   dicated,  with no discharge,  thereby eliminating regulation.   Total recycle
   can be  accomplished by employing  a degree of  special  processing,  such as RO
   (reverse  osmosis)  and evaporation to remove traces of soluble,  but not haz-
   ardous  salts  that  build up due to the use of city make-up water.  The system
   is designed  to remove industrial contaminants rather than produce potable or
   deionized water.

Typical Analysis of Waste Stream  - Beforeand After Treatment

                                   Before .Treatment    After Treatment

              Methylene  chloride...   >   100  p,pm            0.03 ppm
               Phenol	   4,500  ppm           <0.10 ppm
               Chromium	       67  ppm            1.00 ppm

A  Success  Storv

A  major  aircraft paint shop has been operating with this  on-site system for over
a  year.   Prior  to  installing  this  system, they were collecting and drumming up
paint  stripping waste for haul-away  at  a  cost of  $486 per drum.   The  advantages
are  reflected in  the  comparative cost  data  over a nine-month period  involving
the  treatment of fifteen (1,800  gal) batches or  2,700 gallons of  stripper  waste
for  $865 per batch or a total cost of $12,970.

            Contract disposal costs @ $486/drum   $238,582.00
            Disposal costs with on-site  system      12.975.00

            Savings                               $225,607.00

These  data clearly demonstrate that  the waste disposal costs of chemical strip-
ping can be substantially reduced by a customized on-site disposal system,  which
also adds  support for the  continued  use of  the  familiar  and  preferred methylene
chloride based paint strippers.


               Richard A.  Dotson
       Vice President,  Sales  &  Marketing
               Maxi-Blast, Inc.
                 Property of:
               Maxi-Blast,  Inc.
            630 East Bronson Street
           South flend, Indiana 46601
                 (219)  233-1161

The history of plastic media blasting is well known to many.  Early
in the 1980's  the U. S.  Air Force started investigating alternative
methods of stripping aircraft under mandate  by the federal
government.   After much research, the Air  Force concluded that
plastic media blasting was the most efficient and the safest way to
remove paint previously removed by chemical stripping.  Since this
well documented introduction by the military,- many industries have
benefitted from this technology and knowledge now commonly referred
to as plastic media blasting (PMB).

Industrial users have benefitted greatly  from introducing plastic
media blasting to their operations.   Many users have found PBM to
be the  long sought after alternative to  chemical stripping.  The
following examples will  illustrate  instances of successful
implementation of PMB where chemical stripping was once the norm.

                          CASE STUDY 1

A Michigan custom coater had used chemical stripping for years to
remove paint and residue  from various metal surfaces.  An official
there  stated,  "Chemical stripping did not remove the  finish
completely and was not a favorite among our workers".

This company had investigated several methods of  coatings removal
and  finally  decided  that plastic media was the best  of  the
alternatives.   After  implementing  this  blast process,  company
officials noted that  the  finishing cost for  66,000 parts  was
reduced from .11 cents per part  to  less than .2 cents.   In
addition, some parts that were formerly sent to another company for
finishing could now be dry blasted in their facility.   Officials
were delighted to note that without  the use of chemical strippers
there was  no  hazardous solvent  with which to dispose  and no on-
going responsibility for toxic waste.

                       CASE STUDY NUMBER  2

A Midwestern manufacturer of wheel was faced with the problem of
stripping paint from rejects while trying to stay within the EPA
guidelines for chemical disposal.  The chemical method of stripping
used was simple: an aluminum wheel was dipped for a period of time
until  the paint was completely dissolved;   the part was then
removed,  rinsed and repainted.  The potential hazards  of using
chemicals in the method however,  were high and the disposal costs
were  expensive.   Compounding these problems  were the area
government officials paying particular attention to any chemical
disposal methods.  Finally, to  make matters worse,  the  dip tank
process was slow, requiring each wheel to  soak for 4-8 hours before
it could be removed and sent back to production for repainting.  As
the company grew and more wheels had to be stripped, the chemical
process could not keep up with the accelerated growth.

Enter PMB  with the appropriate  equipment and  media.  With  dry
blasting, the paint coating was stripped  from each wheel in 10-15
minutes with no rinsing needed afterwards.  Once  the blasting was
completed, the wheel was reprocessed  through the  painting cycle and
the manufacturer was more than able to keep up  with rejects.   In
addition, EPA officials were satisfied,  disposal costs disappeared
and workers were relieved that dealing with chemical solvents was
a thing of the past.

                       CASE STUDY NUMBER 3

Another Midwestern company was faced with the problem of removing
a vacuum-metallized coating from various sized paint racks.  The
coating was extremely tenacious and,  in many cases, even chemical
strippers  could not  successfully attack and  soften  the metal-
coating bond.  Many times paint racks were used until the coating
build-up was so heavy that the only recourse was to dispose  of the
paint rack completely.   Between the  high disposal costs of the
chemicals and the loss of paint racks due to inefficient cleaning
processes, quite  a  bit  of money was being spent on an operation
that had become a management nightmare.

Again, plastic media solved the problem beautifully. This company
purchased dry blast equipment for approximately $14,000 and, with
less  than  $4,000 per month in plastic media,  was able to blast
clean virtually all  the paint racks  that had previously posed
problems.   Immediately  the benefits  were recognized.   Within 3
months the investment in the equipment and media  paid for itself.
Company officials now saw  the cleaning process as  a cost savings
area not a cost producing area.

                       CASE STUDY NUMBER 4

In  California,  a custom powder  coater was faced with meeting
stringent  EPA  guidelines after having used chemical solvents for
coatings removal for years.  Admittedly, solvent stripping was time
consuming  and  costly.   Each  part  had to be soaked and  scrubbed
repeatedly to  assure  complete cleaning.  The PMB process  had been
heard of  but never  tried.   although skeptical,  company  officials
felt they had no choice but to see if  plastic media would work for

"We found plastic media blasting to  be  much more  efficient than
chemical  stripping, decreasing  company labor expenses  by 25-30%",
noted company  management.    In  addition,  company  officials
recognized a remarkable increase  in  production  efficiency and a
healthier attitude among  employees who were now  not exposed to

What  is  the "hero" of all  these  studies?  Plastic media,  as was
used in  each  of   these cases,  is of precisely-sized,  jagged
granules  designed to chip away paint, coating, or residues.  The
plastic  is available in several grades, hardness and  sizes.  PMB
specialist can pin-point the correct media  choice for almost any
blasting  application.  See table  1.
More  and more, as PMB replaces chemical stripping,  former skeptics
become  converts.  One  former chemical solvent user who had been
exclusively devoted to the chemical process  for over  eight years
comments,  "Plastic  media  stripping is  the only feasible,
ecologically safe way to depaint  and  strip products"-

As for the toxic dangers involved  in PMB, a leading manufacturer of
plastic media  states, "There is nothing in the plastic media that
 it considered  toxic, however, any toxic paint  or coating being
 removed  might  necessitate special waste handling.  It is  best to
 consult the state and  local regulations  to be safe".   In many
 cases,  however, the resulting "dust"  can be simply thrown  away.

Who are good candidates  for PMB?  There are many, but, in general,
any  company that needs to strip or clean a product and  is
prohibited from using chemical solvents or  can't run the risk  of
using harsh abrasives,  should consider  plastic media blasting.

The  conversion  cost  of changing from  chemical  stripping to PMB
could  actually  be considered the  first  steps to cost  savings.
Depending on  the  part(s)  to  be  finished, many companies require
only an appropriately-sized blast cabinet, an adequate air supply
and  electrical power  and the media  itself.   In  many cases,
companies can make this  conversion for less than  $15,000 providing
no additional air and electrical power  is need.

Compare these  costs with the  cost of using  solvents in most
facilities.   Using the  Air Forces'  experience with  the  F-4,  for
example, the results  are dramatic.   The Air Force found that once
the plane was stripped using chemicals there were 20,000 gallons of
contaminated water  with which to dispose.   Federal disposal
guidelines were  not lenient and workers  are rarely fond of handling
chemicals or breathing the fumes.   Again,  in this case,  the time
elapsed was a consideration.  Typical stripping time for an F-4 was
340 hours with chemicals; 39  hours  using plastic media.

In summary,  PMB  has mucji to offer the  company looking for  an
alternative to chemical stripping.

     1.   Reduction,  or elimination of  disposal costs.
     2.   Time savings  (labor and processing time).   See Table II.
     3.   A healthier environment for workers.
     4.   A process that will satisfy most guidelines for safe
          handling and disposal  of  waste materials.
     5.   A reduction in the  cost of materials and equipment
          necessary for stripping.
     6.   A process that will successfully strip some parts where
          chemicals fail.
     7.   Increased production efficiency.

As plastic  media blastings matures and regulations continue  to
tighten around  chemical  stripping,  more  industrial  uses will  be
found  for this revolutionary process.   Additionally, with
environmental and  ecological  issues more important  than ever  to
industry, the change to  PMB  is  a logical and responsible choice.
The  increased use  of PMB is  a sensible and safe alternative not
only for our world, but the individuals that inhabit  it.


                         AND APPLICATIONS

Granulated Polyester

Granulated Urea

Granulated Melamine
Granulated Acrylic

Extremely sensitive or thin
substrates; delicate parts.

Aircraft propellers; aluminum
automotive parts.

Paint hooks and racks; office
furniture; military ground
transport vehicles; industrial

Automotive bodies  (especially
fiberglass); airframes;
aircraft wheels and rims.
           Used courtesy of Products Finishing magazine.


                      VS.  CHEMICAL STRIPPING
Aircraft propellers

Automotive rims

Paint hooks

Automotive bodies

Office furniture

Aircraft wheels

Fiberglass boats
Military ground

    5 min.

    8 min.

    3 min.

    2 hrs.

    15 min.

    8 min.

    2 hrs.

    4 hrs.

    25 min.

    60 min.

    20 min.

     2 days

    3.5 hrs.

     2 hrs.

  not able to
strip chemically

     2 days
          Used courtesy of Products Finishing magazine.


                                 Bob Kerr
                                 February 1991

The  removal  of coatings  using  plastic media in  a  dry stripping
process  has  continued to  gain  ever-increasing acceptance  and
popularity.  The process itself  is actually a refinement entailing
substantially  increased precision of  control  of a much older and
generally known type of impact finishing - abrasive blast cleaning.
The  first sandblast machine was designed  and  manufactured  in
Philadelphia in  1870.   As the  process evolved  over the years, a
high degree of concentration was placed on control of the variables
in the  abrasive  blasting process  with most  of  the concentration
directed towards maximization of the kinetic energy imparted on the
surface, usually with  the intent  of both removal of contaminants
or coatings and a resultant etch  for mechanical bond.

Though the objectives and application of  the dry stripping process
are  far  different  from  classic  abrasive  blast  cleaning,  the
examination and control of  the  parameters of the process entails
use  of  many  of the same  criteria.  This is  especially true with
regard to the  "media," or in the  case of abrasive blast cleaning,
the  "abrasive" itself.


The  characteristics  of  abrasives evaluated  for  use in blast
cleaning include both  the physical and chemical properties of the
material used.  "Physical" properties evaluated include the mass,
size and cleanliness,  the hardness,  the  toughness,  and the shape
of the materials.   "Chemical" properties evaluated vary depending
upon the  application but are usually  directed  towards degree of
operator protection required and the potential of  the material for
contamination of the surface being blasted.

There is a distinct relationship of the properties of abrasive with
the work performed.  Abrasive blasting, dry stripping,  or any type
of impact cleaning is  essentially a mechanical process.  A match-
up is  required  with  all of the parameters of  the  process  in
relation to the nature of  the surface  to  be cleaned, the nature of
the desired material to be removed and the nature of  the substrate.

Of course, the nature of the desired surface finish represents the
end result of the application of the process.

Typical abrasives in blasting are oftentimes natural products which
are  quarried   or   processed  based  on  selection  for  optimum
combination of  physical and  chemical properties.  By their nature
"naturally  occurring"  products may  take different forms  from
different sources,  as well as different purities or variations in
the properties.  There  may also be the presence of elements that
are hazardous to the operator or the work to be performed.

Synthetic abrasives, or those that are manufactured from particular
elements with the intention of maximizing the physical properties,
have in  the  past also been  subject to variations  from different
sources or batches.  The variations, while much more controllable
in a synthetic  material,  such  as,  aluminum oxide,  were developed
for  a  more  primitive form  of  abrasive blast  cleaning  and  are
acceptable only within those fairly wide parameters.

Typically, in  abrasive blasting,  a user would adjust  the other
process  variables  to accommodate  for  variations in the abrasive
most  readily available  to  him.    In  fact,  in some  instances,
subsequent processes,  such as  the  priming or coating  or bonding
might have to be  adjusted to accommodate the surface finish that
resulted from the available  abrasive.

Typically,  abrasive  blasting   has been a relatively  imprecise
process with fairly wide  parameters for the  acceptable grades of
finishes  required   for  subsequent  processes,  such as  coating or
bonding.  The direction of abrasive blasting towards satisfying its
applications have,  in general, been  toward  "minimum"  standards.
Design  tolerances  of related  processes  recognized these  wide
parameters and  accommodated  them.

There are exceptions to the wide tolerance  levels found in classic
abrasive blast  cleaning.   While it is a very aggressive process,
it is  sometimes controlled  for repetitive use  in  more technical
applications.  This control, in a large part, was highly dependent
on the consistency and  characteristics of  the abrasive employed.
As a process, abrasive blasting has been used to provide the final
surface  finish,  including satin finishes,  high tolerance "clean"
surfaces, or controlled peened effects on a substrate.  The key to
obtaining a  more technically controlled finish  is  an absolutely
predictable  and repeatable  combination of the  parameters of the
process,  including  the  abrasive,  or  in  the  case  of  the  dry
stripping process,  the media itself.

Silicon Carbide
Fused Alumina
Chilled iron
Steel Shot/Wire/
Silica/ Sand
Quartz/ Flint
Metallic Slag
Glass Beads
Plastic Media
Iron with 2.85% C.
1 35% SiO,; 03%
Mn: 0.14% S.
004% P
Fe^l? (Si04)3
Steel with 06-1 25%
C: 02-1 1% Si02.
1 25% max Mn:
0 08% S; 0.08% P
MgFeAl Silicate
32-45% SiO?. 25-33%
CaO + MgO. 24-35%
28-37%SiO?. 16-21%
CaO + MgO: 30-45%
(MgFe)? SiO,
Soda-lime glass
Mel amine


Plastic media  used in the dry  stripping  process  is probably the
most synthetic and, therefore, controllable material used in impact
cleaning.   The  material is  referred to  as  media,  in general,
because it does not have the severe "abrasive" characteristics of
materials  used  in conventional  abrasive blast  cleaning.    The
material is specifically designed within very tight tolerances to
produce  a  much  less  aggressive effect than  blast cleaning.   A
comparison  of   the  generally  available  plastic  medias   with
conventional abrasives in Figure 1 highlights  the much "softer"
nature of  the  material on the  Moh scale due to  the  much higher
concern for retaining the integrity of the substrate.  In fact, the
other materials evaluated in Figure 1  would, without exception, be
considered serious contaminants if found in plastic media.

The plastic medias currently used in the dry stripping process are
manufactured from cured polymer resins.  Initially,  thermosets such
as  polyesters  and  urea polymers were used.   However, as  newer
applications and user  techniques have expanded, so have the range
of  media  base  polymers.   Important to the media  quality is the
tight control  of  the polymer characteristics  during manufacture.
The manufacturing  process concentrates on producing  the  optimum
combination  of  physical properties  in  an  essentially  neutral
chemical particle.



Plastic media has a bulk density of 40 to 57 Ibs. per cubic  foot,
with a specific  gravity in the range of  1.15 to  1.50.   In  rough
comparison to  the  abrasives  shown in  Figure  1,  silica sand  has a
mass of about  100 Ibs.  per cubic foot, while the steel grit has a
mass of about 250 Ibs. per cubic foot.  As the process entails the
imparting of kinetic energy to the surface in a controlled fashion,
this lighter mass is a  key factor in producing the "non-aggressive"
effects desired  in  the dry stripping  process.   This mass  is also
controllable in  the manufacturing process by the media supplier.
With the low velocities used in the dry stripping process (due to
the   lower  operating   pressures   employed  when  compared  to
conventional  abrasive  blasting),  the  impact   force   should  be
controlled to affect and remove only the desired coating layer or
layers with minimal ancillary effect.


The size and cleanliness of the media  as a physical property, also
affect the  impact  cleaning.   With  a  fixed mass mentioned above,
size can, within a  certain range, determine impact force  and degree

of penetration in the  coatings.   Size  is  also a key  factor in
producing  the  physical characteristics  of  the  finished surface,
including evaluation for depth of penetration, if any.  Size, also
as a characteristic, entails cleanliness.  Cleanliness examines for
the presence of undersized material as an indication .of the quality
control  employed in  the manufactured  process.   Media  size is
normally a mix, or range, of screen sizes that can be as tight or
broad as necessary.  In addition, the mix of sizes  can be effected
by actual blending of various size materials (of  the same hardness)
in different percentages to obtain a working mix.   In either case,
proper quality control would not allow  for the inclusion of any
significant  levels  of  fines  or  undersized  material   (outside
specified  parameters  for that mix  size).   Fines  do not  aid the
process. They  only produce  unnecessary dust and take up valuable
space in the air  stream during the media propulsion.


Hardness  is,  as mentioned  above,  one  of the  key aspects of
differentiation of  plastic "media" from the general  category of
"abrasive."   Plastic  media  is generally currently  available in
three basic hardnesses  on the Moh scale  (1) of 3.0, 3.5, and  4.0.
The  3.5 media,  with its mid-range hardness  has the broadest field
of applications.  The  hardness factor is a  matchup to the coating
to be removed as well as the substrate characteristics.  Generally,
hardness  is  not  a  "mixed"  result.   While various sizes  may be
blended  to working mix,  most users  prefer specific,  consistent
hardness  characteristics.   Each  particle  ideally  would  be of
identical  hardness to  the other particles in the media.  Hardness
within a certain range is a function of the controls employed in
the  manufacturing process.

                           MOH HARDNESS

                    TALC                 1
                    ALUMINUM             2 TO 2.9
                    COPPER               2.5 TO 2.9
                    BLACK WALNUT SHELLS  2.9

                    PLASTIC MEDIA        3.0 TO 4.0

                    CORN COBS            4.5
                    IRON                 4 TO 5
                    GLASS                4.5 TO 6.5
                    APATITE              5
                    STEEL                5 TO 8.5

Figure 2.  MOH  Hardness Table


Toughness is a phrase generally employed in relation to abrasives
to indicate  their "non-friability"  or resistance to breakdown of
the media to particle sizes outside the range of the desired mesh
size of the working mix.  Toughness  is a characteristic related to
hardness in a general sense in that harder materials are normally
more brittle.   In  synthetic  abrasives or media,  however,  other
elements can be included to provide for a more resilient particle
while   still  maintaining   appropriate   surface   hardness   and

Toughness is also difficult to measure,  A "shatter" index exists
for some manufactured abrasives.  This is really an indication of
the number of particles created by the impact of a known force on
a predetermined number of particles.  The actual importance of the
toughness of the media and, therefore, the only realistic measure
of the toughness is the percentage of  breakdown to a particle size
outside the desired parameters in actual use.

Friability  may also  be  an  indicator of  inconsistency of  the
material.  If, for instance, different types of resins are mixed,
particle segregation can take place.

In general,  plastic media  has  an  attrition  rate  of 5% to 10% per
application.   This  attrition  rate  is  a  function  of  both  the
toughness of  the  media itself, as well as  the efficiency of the
cleaning and reclassification equipment.   Also  important is the
thoroughness of the recovery process.


The shape of  the  plastic  media most successfully employed in the
dry stripping process  is  angular.   While several synthetic media
exists  that  are  extruded  in  various  shapes  for  particular
electronics  applications,  an irregular angular  shape similar to
that found in conventional abrasives, has  proved most successful
in dry stripping on sensitive surfaces.  The shape of the resultant
impact fracture of  the  media  is also important,  and,  in the case
of plastic media,  the  fact that the resultant fractured grain of
media  is  also  angular,  provides   for  consistent  reuse  with
predictable  finish results.


The  chemical  properties  in  plastic  media  are  not  a  positive
contributor to the process, therefore  are ideally neutral.  Plastic
media is essentially inert and there is no change  in reactivity due
to accidental contract with  other materials.   It is  also zero
percent volatile  by volume and not  a combustion hazard.  Several

minimum Explosive Concentration Tests have been run on the various
raedias with  results  indicating that the medias require very high
concentration  of very fine  particles before posing any  type of
explosive hazard.

A  characteristic peculiar  to  plastic  media  which  has  been so
carefully  synthesized is consistency in color of  the particle.
Consistency as a result of production methods and care can provide
the desired combination of physical properties mentioned above from
one particle to the  next in a specific batch  and  from batch to
batch of a specific  grade of media.   If desired, a specific color
can be provided  for  ease  in  identification,  if different types of
media are being stocked by a user.   The  color also helps highlight
contrasting contaminant colors as a visual check on the efficiency
of cleaning  of the media in recycling for reuse.   Color can also
provide a visual check of surface for residual dust for the wash-
down procedure.


           . Mass
           . Size and Cleanliness
           . Hardness
           . Toughness
           . Shape
           . Consistency


           . Consistency
           . Contamination
           . As Appropriate  for Operator Safety
           . As Appropriate  for Environmental Protection
           . As Appropriate  for Application and Workpiece
            (Surface or Substrate Contamination or Reaction)

Figure 3.  Properties for Evaluation of Plastic Media


The phrase  "controllable in the  manufacturing  process"  was used
repeatedly in the evaluation of the characteristics of the plastic
media.    Unlike  sourcing  naturally  occurring  abrasives,  the
production of,  and  hence the control of the variables of plastic
media, should be a very precise process.  Though the manufacturing
process  and actual  compounds  of  any supplier  of  this  type  of
material is maintained as a trade secret, several process variables
are critical to the adherence  to tight tolerances between batches
and between particles within a  batch of the finished product.  This
consistence, therefore, does affect the predicted repeatability of
the stripping process.

Electron microscope scans are used to evaluate the elements of the
material  for both the  presence of undesirable elements  and for
consistency  of  compounding.    No heavy metals,  such  as chromium,
found in some pigments,  should be present.

Two basic sources of  raw material are used in the manufacture of
media.      Discard   materials   from   molders   and/or   virgin
resins/compounds.  Theoretically, discard moulded material can be
used to manufacture acceptable quality media if the discard molded
material is  of  properly specified compounds and are properly and
completely cured.  Consistent  media quality is, however, at risk,
even when very  close  and frequent checks are made to the discard
molded material.  Both the presence of contaminants and incomplete
compound cure are difficult to detect in discard material.

Use of virgin compounds/resins on the other hand offer substantial
control over quality  and consistency,  particularly when moulding
process is performed at  the manufacturers plant.

Plastic  synthetic media has,  by the  nature  of the controlled
manufacturing process, a unique ability allowing for the variance
of  the  specification  requirements within  certain  parameters  in
response  to  user needs.   As the dry stripping  process  has been
developed, the  critical aspects of properties  of  the media have
also  been refined.    Only a "manufactured  media" can respond to
these   evolving  requirements  and  the   continually  evolving
specifications  of this process.

When  users  advised that the presence of  any  metallic particles
might adversely affect the surface, a manufactured media could be
adjusted  to  eliminate this  material.   Presence  of  such foreign
materials  and   their  ability  to  impregnate in the  substrate is
clearly seen by examination of the non-plastic abrasives in Figure
1 discussed  above.

When  it  became apparent  that  some users felt  concern  about the
neutrality or  alkalinity (pH)  of the media, a manufactured media
could be modified to confine the neutrality within a specific pi-
hydron range.

When  users  requested a media of a single "contrasting" color to
assist in identifying the presence of contaminants in material for
reuse,  and  the presence of  residual dust  during removal and
washdown, a manufactured media could respond cooperatively to this

Hardness can be varied to suit (within a certain range) and then
reproduced repeatedly with a manufactured plastic media.  Size can
be controlled  and  provided batch to batch with a quality control
possible  only  in  manufactured media.   Shape, mass,  almost any
variable could be controlled within certain parameters and produced
repeatedly in  a manufactured plastic media.

"Precision control" of such an absolutely critical variable as the
media  in  the dry stripping process  through careful,  consistent,
production of a synthetic material is the only logical approach to
obtaining the  level of confidence necessary to repeatedly employ
the dry stripping process.  Grumman Aircraft, in their test program
of the process, concentrated significant effort in evaluation of
the  media.    Their  report  takes  great  care  to  point out the
implications of indications of contamination through the presence
of sulphur chlorine and  lead contaminants, as well as composition
inconsistencies and the  unknown effect  this  might have  on the
consistent application of the process.

The process  itself has a  series of typical work requirements that
must  be addressed  and,  in part,  these requirements are addressed
through  the  matchup  with  the  appropriate  media.    A  typical
stripping job entails the removal of a coating or contaminant, such
as carbon,  perhaps with  selective layer-by-layer  control  of the
removal  process.   It  is  critical,  generally, to maintain the
integrity of the substrate protecting against  excessive material
removal, or  change in the substrate physical properties, such as,
through peening or fiber damage.  Also required is protection from
impregnation  or   intrusion  into   the  substrate  with  foreign

Use of the dry  stripping  process also  satisfies work requirements
not related  to the  surface itself, but more to considerations of
the operator, the environment, and the economics and productivity
of coating   removal.   With plastic media  stripping  there  is  a
reduction in the requirement for  neutralization of toxic materials
and  their   disposal,  considerably  improved   production  rates,
substantial  operator  visual inspection,  and  a  reduction  in the
operator's exposure to hazardous work.

In addition,  dry stripping provides for the ability  to  vary the
process   to  match   specific   surface  conditions   and  finish
requirements.   The increased use of composite  materials and the
differences in  their surface properties  can only be consistently
addressed by  varying the parameters of the dry stripping process
to suit a particular new material.

As  development,  evolution,  and  precision  control  of  the  dry
stripping process continues, there is a strong indication  that this
is the only method that can be expected to keep pace with  the rapid
advancements  in  aircraft  materials that  we can  expect  in  the

                                 Harold F. Haag

                                Aqualon Company
                             2711 Centerville Road
                                 P.O. Box 15417
                           Wilmington,  DE 19850-5417
                          International Conference on
                        Reducing Risk  in Paint Stripping
                              February 12-13, 1991
                              Washington,  DC, USA

                            Conference Sponsored by
                 United States Environmental  Protection Agency

      Paint removers based on N-methyl-2-pyrrolidone  (NMP) in combination with
propylene glycol methyl ether acetate and mineral spirits were prepared and
tested for effectiveness on a variety of coatings versus commercial paint
removers.  Typical polymeric thickeners such as hydroxypropylcellulose (HPC)
and methylhydroxypropylcellulose  (MHPC) were not soluble in the experimental
solvent formulations.  Ethylcellulose (EC) and ethylhydroxyethylcellulose
(EHEC) were soluble.  EHEC was used to thicken the experimental paint remover
formulations because of its greater efficiency.  The  experimental NMP-based
paint removers generally performed well relative to a methylene chloride-based
paint remover and non-methylene chloride paint removers.


       Concerns about the health and environmental  effects  of methylene
 chloride  have prompted interest in alternative  solvents  for paint removers.
 N-methyl-2-pyrrolidone (NMP)  is an attractive alternative  solvent because of
 its  low toxicity,  low evaporation rate,  high flash point and good solvency.
 However,  the relatively high  cost of NMP requires  it  to  be diluted with other
 solvents  in order  to obtain reasonable economy.  Polar solvents  such as
 alcohols  and ketones tend to  reduce the effectiveness of NMP when used as
 diluents  [1].   Aromatic hydrocarbons,  on the other hand, have been found to
 improve effectiveness while providing economical dilution  [1,2].  Ternary
 blends of NMP,  glycol ether ester and aromatic  or  aliphatic hydrocarbons have
 also been demonstrated to be  effective paint removers [1] .  In the case of
 combinations of NMP with aliphatic hydrocarbons, the  third solvent such as
 propylene glycol methyl ether acetate (PM acetate) must  be included to effect
 solution  because NMP is not miscible in aliphatic  hydrocarbons.

       Modified cellulesic polymers are commonly used  to  thicken  methylene
 chloride-based paint removers [3,4]  and have been  used successfully to thicken
 NMP-based paint removers.   Ethylcellulose (EC)  and hydroxypropylcellulose
 (HPC)  are reported to be effective thickeners for  combinations of NMP and
 aromatic  hydrocarbons [2,5].   Methylhydroxypropylcellulose (MHPC) is reported
 to be  effective in a combination of NMP,  aromatic  hydrocarbon and benzyl
 alcohol [6].   However,  in a solvent system composed of NMP, glycol ether ester
 and  large amounts  of aliphatic hydrocarbon,  the traditional cellulosic
 thickeners  would not be expected to be effective because of their lack of
 solubility  in aliphatic hydrocarbons.   Ethylhydroxyethylcellulose (EHEC),
 though, should be  an effective thickener for such  a solvent system because of
 its  high  tolerance for aliphatic hydrocarbons.

       The purpose  of this  research was to identify polymeric thickeners for a
 paint  remover based on a combination of NMP, PM acetate  and mineral spirits
 and  to evaluate the thickened paint remover versus commercial products based
 on methylene chloride and alternative solvent systems.

      The materials used  in the  experimental paint remover formulations are
listed in Table  1.  Four  modified cellulosic polymers were tested for
solubility  in the combination of 30:40:30 parts by weight of NMP:PM
acetate:mineral  spirits.  Two types of mineral spirits  (MS) were tested:  a
regular grade (Sun T) containing 18% aromatics, and an  odorless grade (Shell
Sol 71) which contains less  than 0.1% aromatics.

      Solution properties are listed in Table 2.  Only  EC and EHEC were
soluble in  these two solvent systems, and the EC solution containing odorless
mineral spirits was very hazy, indicating borderline solubility.  Viscosities
were measured at 23 °C (73 °F) using a  Brookfield LV viscometer  and  a #2
spindle at  12 rpm.  EHEC XX  High displayed better thickening efficiency than
EC T-350 and was thus chosen as  the thickener for the two experimental paint
removers based on these solvent  systems.  The compositions and physical
properties  of the two experimental paint remover formulations are listed in
Table 3.

      Five  generic  coating types were selected for the paint remover
evaluations (Table  4).   These  coatings were applied to wood and metal panels
to form the coating/substrate  systems listed in Table 5.  The latex paint on
pine wood was  at  least  six years old.  The nitrocellulose furniture lacquer
was a formulation of 40:50:10  parts by weight nitrocelluloseralkyd
resin:plasticizer.  The commercial alkyd, epoxy and two-component urethane
paints were applied to  Bonderite Spra 100 zinc phosphate-coated steel panels
from Parker-Amchem  and  were cured according to the paint manufacturers'
instructions.  The  cured paints were tested by methyl ethyl ketone (MEK)
double-rub  testing  for  completeness of cure with the results also shown in
Table 5.

      Three commercial  paint removers were selected as controls for the
performance evaluation.  These commercial paint removers were based on the
solvent systems described  in Table 6.

      The paint remover evaluations were conducted by pouring approximately
three milliliters of paint remover onto each coating and measuring the time
for the coating to  lift or to  soften to the point where it could easily be
scraped off with  a  putty knife.

      The experimental paint removers based on NMP gave performance equal to
the methylene chloride-based commercial control on latex paint and were
slightly faster to soften furniture lacquer, although all of the paint
removers tested softened these two thermoplastic coatings in only a few
minutes.  Test results are presented in Table 7.   The latex and lacquer
softened and remained in complete contact with the wood substrates (did not
lift) under the action of all of the paint removers, and thus only time-to-
soften was measured for these coatings.

      The alkyd paint was lifted by all of the paint removers--very quickly by
all except the dibasic esters-based control--and thus only time-to-lift was
measured for this coating.

      Although the experimental NMP-based formulations did not lift the epoxy
or the urethane, they softened the epoxy quickly and softened the urethane
faster than the dibasic esters-based control.  The methylene chloride-based
control lifted the urethane paint very quickly and lifted the epoxy primer in
reasonably short order.  The methanol/toluene/acetone -based commercial control
softened both the epoxy and urethane quickly but needed more than eight hours
(overnight) to lift these two coatings.  For the epoxy primer and the two-
package urethane, both time-to-soften and time-to-lift (if lifting occurred)
were measured with the exception of the methylene chloride-based remover on
the urethane paint, which lifted too quickly to measure time-to-soften.

      The experimental NMP-based formulations and the dibasic esters-based
commercial remover tended to keep the coatings soft for very long times (48
hours or more) compared to the methylene chloride- and
methanol/toluene/acetone-based controls.  This advantage is the result of the
very low volatility of NMP and dibasic esters.  Paint removers based on these
solvents do not need evaporation inhibitors.

      The odorless mineral spirits in experimental Formulation #2 had the
advantage of giving a flash point over 100 °F.  Slightly longer times
were required by this formulation versus regular mineral spirits to soften
some of the coatings, but the ultimate effects on the various coatings by the
two experimental formulations were the same.

      The flash points of both experimental paint remover formulations were
unexpectedly low.  The component with the lowest flash point in Formulation #1
is the regular mineral spirits at 103 °F,  but the composition flashed at 89
°F.   In Formulation #2,  the PM acetate has the lowest flash point (116 °F),
and the odorless mineral spirits has a flash point of 125 °F,  but the
composition flashed at 102 °F.  The flash point of NMP is 199 °F.   These
results indicate that the combination of NMP, PM acetate and mineral spirits
exhibits a negative azeotrope [7] and that the choice of mineral spirits will
determine the flash point of such a mixture.

      Paint removers based on NMP diluted with PM acetate and mineral spirits
can be effectively thickened with EHEC XX High.  Such paint removers performed
favorably relative to commercial methylene chloride-free paint removers tested
that were based on alternative solvents other than NMP.  The NMP-based paint
removers performed favorably relative to a commercial methylene chloride-based
paint remover on thermoplastic coatings and on a thermoset alkyd, but were not
as effective as the methylene chloride-based product on two other thermoset
coatings.  The NMP-based paint removers do not require an evaporation retarder
and have the the advantage of keeping coatings soft for much longer periods of
time than methylene chloride and highly-volatile alternative solvents.  The
NMP-based formulations have the advantage of reduced flammability over
commercial products based on combinations of methanol, toluene and acetone.


[1]  Sullivan, C. J., "Solvent Based Paint Strippers:  Alternatives to
     Methylene Chloride," Presented at the Annual Meeting of the
     Federation of Societies for Coatings Technology, October 30,  1990.

[2]  Palmer, D. A., "Paint Remover with Improved Safety Characteristics,"
     U.S. Patent 4,120,810 (1978).

[3]  Martens, C. R. , "Paint and Varnish Removers," Technology of Paints.
     Varnishes and Lacquers. C. R. Martens, Ed, 615, Robert E. Krieger,
     Malabar, FL, 1968.

[4]  Mallarnee, W. R., "Paint and Varnish Removers," Kirk-Othmer Encyclopedia
     of Chemical Technology. 3rd Ed, Vol 16, 763, John Wiley & Sons,  New
     York, 1981.

[5]  Nelson, H. J., "Paint Stripping Composition and Method of Making and
     Using Same," U.S. Patent 4,749,510 (1988).

[6]  Francisco, R. L. "Paint Stripping Composition Having Reduced Toxicity,"
     U.S. Patent 4,732,695 (1988).

[7]  Durrens, T. H., Solvents.. 8th Ed., 55, E. H. Davies, Rev, Chapman and
     Hall, London, 1971.

                             Table 1
                   Paint Remover Raw  Materials
  EC T-350 Ethyl cellulose (EC)
       Aqualon Company

  EHEC XX High Ethylhydroxyethylcellulose (EHEC)
       Aqualon Company

  Klucel«-H PR Hydroxypropylcellulose (HPC)
       Aqualon Company

  Culminal« MHPC 20,000 S Methylhydroxypropylcellulose (MHPC)
       Aqualon Company

  N-Methyl-2-pyrrolidone (NMP)
       BASF Corporation

  Propylene glycol methyl ether acetate (PM acetate)
       Arco Chemical Company

  Sun T regular mineral spirits
       Sun Company

  Shell Sol 71 odorless mineral spirits
       Shell Chemical Company
                             Table 2
       Solution Properties of Modified Cellulosic Polymers
           in 30:40:30 NMP:PM Acetate .-Mineral Spirits
             Concentration,          Viscosity, mPa»s (cps)
              Parts per 100
Polymer       Parts Solvent      Regular MS       Odorless MS
  EC              6.0               1,010            1,080
  EHEC            4.0                 955              860
  HPC             0.5             Insoluble        Insoluble
  MHPC            0.8             Insoluble        Insoluble

                           Table 3
      Experimental NMP-Based Paint Remover Formulations

   PH acetate
   Regular mineral spirits
   Odorless mineral spirits
   EHEC XX High

         Total weight


   Viscosity, mPa«s (cps)
   Density, g/L

   Flash point,
      Tag closed cup, °C
   Solution quality
               Parts by Weight
                 1         2






                Water White,
                Slightly Hazy
                           Table 4
         Coatings Used in Paint Remover Evaluations
Latex Paint

Furniture Lacquer

Alkyd Paint

Epoxy Primer

Two-Package Urethane
Unknown gray latex paint.

Nitrocellulose lacquer.

Benjamin Moore Impervo alkyd enamel
#133-5A TG-4X8, WH-2X, aqua green

PPG DP-40 epoxy primer, olive green

PPG Durethane polyester-urethane
enamel, black

                                 Table 5
                        Coating/Substrate Systems
Solid White Pine
Birch-Veneer Plywood
Bonderite Spra 100
Bonderite Spra 100
Bonderite Spra 100
Thickness, Hi Is
Solvent Resistance,
     MEK Rubs
       No Test
       No Test
   60, Film Broke
  200, Dulling
  200, No Effect
                                  Table 6
                          Paint Removers  Evaluated
       Paint Remover
      Commercial #1
      Commercial #2
      Commercial #3
      Experimental #1
      Experimental #2
                        Solvent Composition
              Methylene Chloride/Methanol
              Dibasic Esters
              NMP/PM Acetate/Regular Mineral Spirits
              NMP/PM Acetate/Odorless Mineral Spirits
                                 Table 7
                        Paint Remover Comparison
               Time to Soften (S) and/or Time to Lift (L)
                    In Minutes Unless Overnight (ON)
Commercial #1
Commercial #2
Commercial #3
Experimental #1
Experimental #2

            Solvent Recovery Using the Brayton Cycle Heat Pump
                                  Nirmal Jain
                               Paul EL Scheihing
                               Program Manager
                         U.  S. Department of Energy
                       Office of Industrial Technologies
 A progression of designs to control volatile organic compound (VOC) emission streams
 using a reverse Brayton cycle are described in this paper. An advanced design, soon to be
 built, is the result of an intensive cooperative effort of 3M, Nucqn International and the
 U.S. Department of Energy (DOE) over the last two years. The new advanced design
 benefited from a development effort started by 3M in 1975. Similarly, Nucon and the U.S.
 DOE have been involved with 3M since the early 1980"s in the development of the Brayton
 Cycle Heat Pump  (BCHP) for solvent recovery, recycle and reuse.  The technical
 performance along  with the estimated costs of an 8000 SCFM BCHP (that is used in
 conjunction with solvent concentrating adsorption beds) at a 3M manufacturing plant is

The use of solvents in industry is widespread. Solvent use affects a large cross-section of
products such as adhesive tape, plastic foams, synthetic fibers, electronic components,
furniture manufacturer and many more. Recently, environmental concerns have prompted
stricter legislation to control VOC emissions (Le. The dean Air Act).  At the same time the
price  of some solvents has increased significantly forcing industry to search for cost
effective alternatives to manufacture profitably yet within environmental regulations.
Industry is thus presented with the following choices:

    1 ) Fnminarr the need for solvents in the manufacture of their product.
    2) Reduce VOCs by making the process "tighter" (Le. prevent fugitive emissions).
    3) Control VOCs by incineration or destruction.
    4) Control VOCs by capturing and recycling them back to reusable solvent.

 3M uses solvents to manufacture a variety of products (eg. adhesive tape", magnetic tape or
 discs, and  other products requiring coating).   A  corporate wide effort has  been
 implemented by the top management to reduce VOC emissions by 90 percent by the year
 2000. Therefore, all of the four choices above are being considered,

 Controlling VOCs by capture on activated carbon adsorption beds is common in industry
 today. Although the number of solvent control devices number in the thousands in the
 U.S., the level of VOCs that are uncontrolled is by far greater. The U.S. DOE recognizes
 the expanse of solvent recycling throughout the nation as an opportunity to save a
 significant amount of energy (50 trillion BTUs annually valued at over 200 miHion dollars).
 This energy savings will result from more energy efficient VOC control equipment to be
 brought to the marketplace and the saving of the embodied energy of the solvent (Ls. the
 aggregate of the  process energy and feedstock fuel heating value energy required to
 manufacture the solvent is the embodied energy).
DOE Proiect Objective* and G
There are two main goals of this project
    GoaJ I  The first goal is to demonstrate economic solvent recovery for large VOC
            emission points (c,g. a 1000 ton per year VOC source).  A payback of less
            than three years  based on the total installed cost of the equipment with
            solvents  moderately  priced at 30 cents per pound, independent of
            environaacatal regulatory costs, is a target that DOE and 3M want to achieve.

    Goal 2 The second goal is directed at small solvent users of less than 500 tons per
           year.  The mobile BCHP should demonstrate to small solvent users (100 tons
           per year on average) that the annualized costs of this technology can control
           many different types of VOC sources at under S1000 per ton.

Of course, these two goals must be achieved concurrent with reliable equipment, energy
efficient equipment and equipment able to meet environmental regulations,

      Project Application  Areas
   T   r    VOT Control Alication
   3M and the U.S. DOE are working cooperatively to develop an advanced BCHP
   system. DOE will fund 3M (on a cost sharing basis) to design, manufacture and field
   test an 8000 SQFM BCHP system that will be installed at the 3M Greenville. SC
   manufacturing plant to control a 1000 ton per year VOC emission source,  Nucon
   International of Columbus, Ohio, is assisting 3M on this project by providing process
   engineering, equipment design and, manufacture and installation of the packaged
   BCHP regeneration/VOC adsorption system.

   The Small VOC Control Application

   The Greenville plant application is a relatively large VOC control application, VOC
   emission source greater than 500 tons per year probably accounts for less than 10
   percent of the  total VOC emissions.  Therefore, DOS will cooperatively work with
   Nucon International to cost effectively develop a BCHP to control small VOC emission
   points (e.g. less than 500 tons per year). This project will mobilize the BCHP and thus
   allow a single  mobile BCHP system to regenerate numerous concentration beds at
   scattered industrial host site locations. In this way the capital cost of the mobile BCHP
   (estimated at S300.000 to $400,000) can be distributed amongst many industrial

    solvent users.  Southern California Edison (SCE) and Tne Electric Power Research
    Institute (EPRI) arc co-sponsoring this projcc: v-'ith Nucon. 3M and the DOE, and
    therefore, the host sites will be located in the Southern California area. Figure 1 shows
    the small mobile BCHP system that will initially be demonstrated to four companies in
    Southern California. Applicability of the Brayton concept in solving ihcir specific VOC
    recovery problem will be evaluated.
               Figure 1 - Small Mobile Brayton Cycle Heat Pump System
              of  the  Bravton. Cycle
The BCHP is an alternative means of condensing solvents from a gas stream by use of a
reverse Brayton cycle.  Many solvent screams must be refrigerated to temperatures  below
- 50°F (-45°C) to condense greater than 90 percent of the solvent in a single pass through
the condensing system. Other refrigeration methods, such as a reverse Rankine cycle using
refrigerants in a closed cycle loop can be and have been used to condense solvents to these
low temperatures.  (Comparison of the Brayton cycle to the Rankine cycle will be given

  To illustrate how refrigeration is accomplished with the reverse Brayton cycle, Rgure 2

  shows an ideal regenerative reverse Brayton cycle on a temperature/entropy diagram. At

  station 1 the solvent laden gas stream is compressed isentropically to station 2. Heai is

  extracted in the regenerator from station 2 to 3 at  constant pressure.  Because heat is

  extracted from station 2 to 3 the cycle is termed a reverse Brayton cycle." If heat was added

  by hear exchange or combustion (such as in a gas turbine power plant or jet engine), then

  the cycle would be a forward Brayton cycle. At station 3 the gas stream temperature will be

  cold enough to condense a majority of the solvents. From station 3 to 4 the gas stream has

  work extracted isentropically in an expander (turbine) to lower the gas stream temperature

  even further.  (Temperatures as low as -150°F (-101°Q can be achieved in a single stage of

  compression and expansion). Essentially all  of the  remaining solvents are condensed at

  station 4.  The work produced by  the expander partially drives the compressor.  The

  remainder of the compressor work requirement comes  from mechanical shaft work input.

  The cold gases at station 4 are then passed through the other side of the regenerator to

  recoup heat at constant pressure to complete the cycle.

 dean Air to Process
  Solvent Lsden
Air From Process
                                        Liquid Solvents Out
         Figure 2 - Description of the Reverse Brayton Cycle with Solvent Recovery

 Although the Brayton cycle requires high speed turbomachincry, this machinery is
 commonly used today.  All air conditioning systems uy4 on commercial and military jet
 aircraft use a reverse  Brayton cycle system.  For  aircraft applications,  the Brayton
 refrigeration method has been selected for reasons of low weight- and high reliability.
 Another application of the reverse Brayton cycle is a cryogenic air separation plants. Here
 too, reliability has been good for over fifty years.  At present, the most common application
 of the Brayton cycle is the automotive turbocharger.
 Project "Background
 As mentioned,  3M has actively pursued the BCHP for the past 15 years.  Bryce Fox (a
 retired 3M engineer) was the champion of this technology and is named sole or joint
 inventor on three 3M patents.  (D.CXC3)

 In 1979 3M funded the AiRescarch Manufacturing Company (a division of the Garrert
 Corporation) to provide a 2000 SCFM prototype Brayton cycle system. This was used to
 process a solvent laden gas stream from an inert gas drier at 3M.  In showing feasibility
 and successful  operation of  this system, the U.S. DOE decided to- fund a larger 9000
 SCFM unit that was installed at 3M*s Hutchinson, MN tape manufacturing plant. Both of
 these systems directly condense the solvents by processing the solvent laden air  (SLA)
 from the coating process through the BCHP.

 Both the  2000 and 9000  SCFM system designed-by AiRcsearch used  specially
 manufactured gear boxes that were  costly. The system installed at the Hutchinson plant
 (sec  Figure 3) shows the gear box coupling the input shaft power (an electric motor
running at 3600  RPM) to a high speed compressor/turbine unit running at 16.500 RPM.

       AT -I7OF
           Figure 3 - Simplified 9000 SCFM 3M Hutchinson Brayton System

Learning from the experiences of the Hutchinson system, 3M worked with Nucon to
design and install the second industrial Brayton cycle system at the 3M Weatherford, OK
plant beginning in 1985. The Weatherford design differed from the Hutchinson design as

   1)  Activated carbon beds are use to adsorb and concentrate solvent from the VOC

   2)  The BCHP is used to regenerate the carbon bed with inert nitrogen gas.
   3)  A molecular sieve is  used as an intermediate step between the adsorption and
       regeneration of the carbon bed to eliminate water (and thus ice formation) from the
       BCHP solvent ladrn nitrogen stream.
   4) A free spindle compressor-expander is used in combination with a rotary blower to
      provide the compressor/expansion package.  That is, the shaft power input to the
      BCHP system was decoupled from the compressor/expander package to eliminate

       the high speed gear box used in the Hutchinson design.  This free spindle
       compressor/expander was a modified design of the Gairett Industrial Products
       Division's largest diescl turbocharger.
Rgure 4 shows the overall solvent recovery process in which the two carbon beds are
cycled between step 1 and steps 2 to 4. That is, while one bed is adsorbing solvents at step
1, the other is being regenerated by step 2 (carbon dehydration), step 3 (carbon solvent
desorpdon with the reverse Brayton cycle) and step 4 (molecular sieve regeneration).

The Weatherford system has been operating for over 1.5 years with over 99 percent up
time.  A more detailed description of the Weatherford process is presented in reference (4)
by Kovach of Nucon,


(2 Beds)

            Step 1
       Solvent Adsorption
      Step 3 - Carbon Regeneration
              (Reverse Brayton Cycle)
                                                            Step 2
                                                     Carbon Dehydration
                           Step 4
                Molecular Sieve Regeneration
      Figure 4 - 3M Weatherford Brayton/Concencaror System - Overall Process

   dvanced Bravton
 In considering the recycle of solvents, equipment selection will be dictated by capital and
 operating cost. The solvent type, VOC stream flow size, VOC concentration level and the
 degree to which the VOC must be controlled (Le. percent recovery) arc all factors
 Influencing cost.

 To illustrate the economics of solvent recycling, the Greenville plant installation costs will
 be detailed for the proposed advanced Brayton design and other alternative approaches to
 controlling the VOC emissions from the coater at this plant. The VOC stream to be
 controlled at Greenville  is an 8000 SCFM  SLA stream  with a concentration of
 approximately 2000 ppmv.   The  solvents used arc heptane, xylene, toluene and
 isopropylalcohol OPA).

 Figure 5 shows the preliminary design of the advanced Brayton system.  The Brayton
 regeneration system will provide a dry inert nitrogen stream for solvent stripping to one of
 the two adsorbent beds and then will remove over 99 percent of the solvents from the
 solvent laden nitrogen (SLN) once the SLN is returned from the adsorption bed.  (The
 other adsorption bed is adsorbing solvents from the SLA stream coming from the coater.)
 This process was developed by Nucon under Phase I of the DOE project. The process is
 trade marked BRAYSORB™. Figure 6 shows the temperature versus pressure plot of this
 system.  Note that the tcmperarurc of the adsorber. is '32Q°F (160°C) and therefore no
 additional process hearing is needed to regenerate the adsorbent beds. This means that
 electricity is only needed to drive the Brayton system eliminating the need for steam
production or auxiliary heating systems.

Hgure 5 - Advanced Brayton/Adsorption System for 3M Greenville Plant
          (Rgure represents Nucon BRAYSORB™ process)
U-120 —
5 40 —
01 0 —
            -so —
                        TURBO COMPRESSOR
                  VACUUM PUMP
                                         PROM ADSORBER
                                   TURBO EXPANDER
                      I       I      I      I       I
                      5      10     15     20    25
                    SYSTEM PRESSURE - PSIA
Hgure 6 - Temperature versus Pressure Plot of BRAYSORB™ Process

Figure 7 shows a generic steam regeneration system analyzed for evaluation purposes to
determine cost competitiveness of the Brayton system to other alternative designs. If the
solvents are not miscible or slightly miscible, a decanting system will separate the majority
of the solvents from the steam condensate satisfactorily.  The contaminated condensatc,
however, will need to be treated by an air stripper.
                                     CCOUNG WATER
     Hgure 7 - Steam Regeneration System with Decanting Solvent/Water Separation

 Figure 8 shows a schematic of a reverse Rankine system, This system has two cooling
 systems, one with a 30eF (-1°C) and one with a -80°F (-62°Q evaporator coil cooling
 temperature,  Tne SLN stream is cooled to -75°F (-59*0 which is the same temperature as
 thai achieved by the Brayton system, This allows for equal comparison of the Brayton and
 Rankine systems since approximately  the same percent solvent recovery should be

                                                              HEAT TO
            COCLMG TOMER
           Hguic 8 - Reverse Rankinc Cooled/Inert Gas Regeneration System
Finally, an incineration system is shown in Rgurc 9. This system is a high efficiency unit
since heat regeneration takes place.  No heat recovery is attempted to provide heat to the
plant's utilities needs. The solvents that are burned account for over 50 percent of the fuel
heating value in the combustion process.
                                         COATING PROCESS
                    HgTire 9 - Regenerative Incineration System

 Tables 1 compares cost and performance of these four systems. Tables 2 to 4 give a cost
 breakdown of the three recovery options. Table 5 estimates installation costs of the VOC
 control options.

     Table 1  - Cost and Performance Comparison of Four VOC Control
                  Designs  for the 3M  Greenville, SC Plant

Equipment Cost
Installation Cost
(See Table 5)
Total Capital Cost
& Period
Energy Requirement
   Economic Factors
   operation hours per year - 8640
   electricity rate • 4cents/Kw-Hr
   natural gas cost - S3.00/MM BTU
   boiler efficiency -  75%
   labor rate - S40pcrHr
   solvent recycle value - 5.12/lb

* Costs are annual    E = Electricity   NG = Natural Gas  MMBH = Million BTU/Kr
             Tablc 2  -  Brayton Regenerated  System Cost Breakdown

               Free-spindle Compressor/Expander                    $ 40,000
               Drive Compressor                                   S 40,000
               Regenerative Hear Exchanger                          S 40,000
               Precooler (water cooling)                             S 10,000
               Piping & Valves                                    S 50,000
               Table 4  -  Rankine Regenerated System Cost Breakdown
                     le (waer cooling)                             S  10.000
               rrcoooung Refrigeration Unit                         S  20.000
               Regenerative Heat Exchanger                         S  20,000
               Super-cooler Refrigeration Unit                       S 150,000
               Regenerator Blower                                 S  10.000
               Hearing Unit                                       5  loioOO
               Piping & Valves                                    S  50.000
               Separators & Receivers                              S  30,000
               Instrumentation & Controls                           S  90,000
               Adsorber Structure (Carbon Steel)                     S  60,000
               Activated Carbon (20,000 Ibs @ S2/Ib)                 S  40.000

               Total Equipment Cost                               S 490,000
               Engineering                                       S  75,000
                                                                 S  60.000
               Total Equipment Cost                                S 625,000

               Table S -  Cost Breakdown of Installation of VOC Control

                                                VOn Recovery
               Engineering                         S  50,000            S  50,000
               SLA Fan. Filter, Cooler, Ducring       S 100,000            S 100,000
               Site Preparation*                     5250,000            5120,000
               Tank Farms                         S 150,000            S    0
               Equipment Installation                 S 100.000            S  40,000
               Process Instrumentation               S  50.000            S  5Q.OQQ

               Total Installation Cost                 S 700,000            S 360,000

               * Add 560,000 for a buflding enclosure on the Rankine system
               * Add 51 00,000 for a cooling tower installation for a S team system

A few conclusions can be made som the above tables:

    I)  All the solvent recovery technologies have lower annualized operating cost than

       incineration, Also, the incremental investment of all three recovery technologies

       over the cost of the incineration system yields a U to 3 5 years payback based on

       the aggregate savings of the recycled solvents and the difference in operating costs

       of the recovery options and incineration,  In the future if the solvent price were, for

       instance, 30 cents per pound for this application then the payback on Brayton and

       steam regeneration system would be less then 3 years,

   2)   The Brayton system casts arc estimated to be competitive with the well established
        recovery technologies. This cost estimate of the Brayton system is for the third
        generation design. Further cost reduction can be expected in the furore. For this
        reason, 3M is pursuing this technology so that their choices on controlling VOCs
        may be broadened. Likewise, the DOE sees the Brayton technology as a vehicle to
        reduce energy consumption of VOC control technologies and, to proliferate solvent
        recycling with more cost effective recycling with both large and small solvent users
        and thereby reduce demand for energy intensive solvent production nationwide.

Summary of the Progression of the Bravton  Cvcle Technology

The main accomplishments over the last 15 years on the Brayton cycle solvent recovery
technology have been to reduce capital cost, reduce energy consumption and improve
reliability of the equipment. Table 6 <"mrnari-y»y the performance of the two 3M Brayton
systems already installed (Hutchinson and Weatherford) and the expected performance of
the planned Greenville plant installation.

               Table 6 - Progression of' Cost and Performance
                    Improvements with  the BCHP at 3M
 SLA Stream Size (SCFM)
 Time period designed & Built
 Solvent Type

 VOC Cone. (PPMV)
 Power Required (HP)
 Equipment Cost
Hutch? n ton
1979 -1984
MEK, Toluene,
1985 - 1987
MEK, Toluene,
Heptane, Xylcne
  Toluene, IPA
(From Table 2)
 (1) Estimated equipment costs in 1990 dollars to replicate the installed equipment. This
    does not include installation cost
In summary, substantial improvements have been made on the Brayton cycle technology,
especially in the last two years.  Stricter environmental regulations for VOCs creates a
demand in industry for VOC conirol equipment at reduced cost  Eghcr solvenr prices will
also further enhance the economics of solvent recycling over incineration. The DOE and
3M therefore remain comraincd to this technology.
A three phase cooperative effort between the U.S. DOE, 3M, and Nucon International is
about to enter the Phase E effort to design and fabricate a Brayton Cycle Heat Pump system
to control an 8000 SCFM VOC air stream. Estimates from a preliminary design shows that

the equipment cost and energy consumption have both been more than halved from the

previous generation design at 3M.  This new and advanced  system is expected to be

operational sometime in 1992. This design will form the basis  for other 3M facilities and

other companies with similar VOC control needs to follow through with implementation of

other cost competitive Brayton Cycle Heat Pump installations.


(1) Heat and Liquid Recovery Using Open Cycle Heat Pump System,
    Brycc Fox, 3M; U.S. Patent #4,295,282, Dated October 20,1981

(2) Vapor Recovery Method and Apparatus,
    Leslie R. Flink. Bryce J. Fox, Mary K. Witzel, 3M
    U.S. Patent #4,480,393, Dated November 6,1984

(3) Heat and Liquid Recovery Using Open Cycle Heat Pump System
    Bryce J. Fox, 3M;  U.S. Patent #4,539,816, Dated September 10,1985

(4) Full Size Industrial Application of the Brayton Cycle Heat Pump  in Adsorption
    Concentrator,  J. L, Kovach,  1989 ASME Winter Annual Meeting, AES-Volume 8
    (Advances in Industrial Heat Pumps Technology - 1989). December, 1989