A Cooperative Project
between the
U.S. Environmental
Protection Agency
and the
Printing Trade
Associations
Nationwide
DRAFT
October
994
SCREEN PRINTING CASE STUDY 2
EPA
TECHNOLOGY
ALTERNATIVES FOR
SCREEN RECLAMATION
In business today, being responsive to the
environment means learning new proce-
dures and using new tools to do the same
job with less environmental impact. Decisions
about the purchase of equipment and chemi-
cals for screen reclamation or other produc-
tion processes depend not only on cost,
availability, and performance, but also on
whether environmental concerns can be
addressed. Addressing environmental con-
cerns means understanding the comparative
human and ecological risks of the alternatives
being considered.
This case study, developed for screen
printers like you, is brought to you by the
U.S. Environmental Protection Agency's
(EPA's) Design for the Environment (DIE)
Program with assistance from the Screenprint-
ing and Graphic Imaging Association Interna-
tional (SGIA). Through the DflE Screen
Printing Project, EPA and the screen printing
' working together to identify alter-
native work practices, products, technologies,
and pollution prevention options that are cost-
e&cttw and safer for yonr workers and the
environment. With a focus on screen reclama-
tion, the DfE Screen Printing Project has con-
centrated on providing the chemical risk and
pollution prevention information, along with
performance and cost information, so that you
arc better equipped to incorporate environ-
mental concerns in your day-to-day business
operations.
As you consider changing your recla-
mation practices, this case study can help you
understand the possible occupational health
and environmental benefits of alternative tech-
nologies. This information, combined with
cost and performance information, is critical to
help you raake more informed decisions
about your chemical usage.
This is the second in a series of case
studies focusing on the screen printing indus-
try that EPA has developed to illustrate how
the DfE concepts can be incorporated into
screen printing operations. This case study
focuses on different technologies that can be
utilized in screen reclamation. The DfE Screen
Printing Project identified seven potential sub-
stitute technologies that may be environmen-
tally safer than traditional screen reclamation,
including: high pressure water blasters, auto-
matic screen washers, sodium, bicarbonate
spray, media blasting, pulse light energy tech-
nologies, stripping technologies, and emulsion
chemistry. This study describes three screen
reclamation technologies that may enable you
to change both the types and amounts of
chemicals you use:
• High pressure screen washers
• Automatic screen washers
• Sodium bicarbonate (baking soda) spray
Of the seven alternative technologies
listed above, these three were selected
because screen printers expressed an interest
in learning more about these technologies.
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DRAFT
October 1994
This case study presents:
• Descriptions of two commercially
available technologies that can
reduce a facility's usage of tradi-
tional solvent-based ink removers.
• Description of a technology now
under development that could fur-
ther reduce the costs and potential
health risks of screen reclamation.
• Comparative cost, performance and
risk information for three reclama-
tion technologies.
The costs and risks for each of
the three substitute technologies are
compared to the costs and risks of a
traditional screen reclamation system.
The traditional system used in the
comparison consists of lacquer thinner
as the ink remover, a sodium perio-
date solution as the emulsion remover,
and a xylene/acetone/mineral
spirits/cyclohexanone blend as the
haze remover. These chemicals were
selected because screen printers indi-
cated they were commonly used in
screen reclamation. In both the cost
and risk comparisons, it was assumed
that these chemicals •were applied
manually to 6 screens per day, each
2,127 in2 (approximately 15 ft2) in size.
High-Pressure
Screen Washers
Two high-pressure screen recla-
mation systems were reviewed. In
addition, the performance of one sys-
tem was evaluated in a print shop as
part the DfE Screen Printing Project.
High-pressure washers typically work
as follows. Excess ink is carded off the
screen prior to cleaning. No ink
remover is applied to the screen. An
emulsion softener or remover is
applied and allowed to work, typically
for anywhere from ten seconds to less
than one minute. The ink and stencil
are then removed by a high-pressure
water blaster sprayed on both sides of
the screen at pressures of up to 3,000
pounds per square inch (psi). If nec-
essary, a haze remover is then
applied and allowed to work. Again,
the high-pressure water blaster is
used to rinse off the haze and the
haze remover. Cleaning usually takes
place in a washout booth where the
rinse water can be collected.
While this technology may
require significant water use, most
emulsion and haze removal products
are formulated to allow discharge to
sewers. Where ink residues in the rinse
High Pressure Washer
water exceed wastewater permit con-
centration limits, such as for suspended
solids, manufacturers also supply a
variety of filters. Some improved filtra-
tion systems allow rinse water to be
reused. Filter wastes are typically dis-
posed of as hazardous waste.
Risk
In general, the benefits of high-
pressure washes are that they reduce both
chemical use (eliminating ink removers)
and worker exposure (less scrubbing
required). The DfE Screen Printing Pro-
ject found that the occupational risks of
this system were notably lower than
the risks associated with the traditional
solvent-based reclamation chemicals.
For the traditional screen reclamation
system, health risks associated with
both daily inhalation and skin contact
with the chemicals, particularly with
organic solvents, were significant. For
the high-pressure screen reclamation
system, health concerns were related to
unprotected skin contact with the recla-
mation chemicals. Dermal exposures
could be reduced dramatically, howev-
er, by wearing gloves. Ecological risks
from discharges to the water were not
a concern for either the traditional sys-
tem or the high-pressure blaster sys-
tem. General population risks from air
releases also were not a concern for
either system.
Performance
Performance of a high-pressure
water blaster was evaluated by DfE staff
at a volunteer printing facility where the
technology was in place. During the
demonstration, the technology's perfor-
mance was very good. On screens with
solvent- and water-based inks, the sten-
cil dissolved easily, leaving no emulsion
residue on the screen. Ink stains on
these screens were completely removed
by the haze remover even before the
waiting period or pressure wash. Recla-
mation results were fairly similar for UV-
curable ink as well.
Cost
The DfE Screen Printing Project
also estimated the cost of equipment,
labor, and chemicals for the high-pres-
sure wash. Assuming that 6 screens are
reclaimed daily and each screen is 2,127
in2 in size, the cost estimate for the
high-pressure washer totaled $4.53 per
screen. This estimate was compared to
that of the traditional screen reclamation
system (using lacquer thinner, sodium
periodate, and a solvent blend). Using
the same assumptions, the estimated
reclamation cost using the traditional
system is $6.27 per screen: 30 percent
more than the high pressure wash, with
the greatest savings coming from the
reduced labor costs for the high-pres-
sure washer. Equipment costs, estimated
at $5,300 (installed) account for just 12
percent of the per screen costs. This
estimate does not include filtration
units, which range in price from $1,300
to $12,000, although maintenance and
operating costs vary widely.
Automatic Screen
Washers
There are several different types
of automatic screen washers, and
although most are used for ink removal
only, automatic systems for emulsion
and haze removal are also available.
The major benefits of automatic screen
washers are reduced solvent losses,
reduced labor costs, and reduced worker
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EFA
DRAFT
October 1994
exposures. The DfE Screen Printing Pro-
ject identified a wide variety of auto-
matic screen washers on die market
and found significant differences in the
chemicals used and costs. Costs vary
Automatic Screen Washer
based on the level of automation (such
as conveyors), system capacity, and
complexity of the equipment.
The basic component of the
automatic screen washers is the wash
unit, an enclosed box that can house a
variety of screen sizes (up to 60 in. by
70 in.). After a screen is clamped inside
the wash unit and the top closed, the
cleaning process begins. A mobile
mechanical arm sprays solvent onto the
screen through pressurized nozzles (30
to 150 psi) for any preset number of
cleaning cycles. Since the systems are
enclosed to reduce solvent losses,
volatile solvents, such as mineral spir-
its, are often recommended because of
their efficacy. There are, however, a
number of alternative formulations
offered by equipment manufacturers.
Used solvent drains off the screen and
is directed to a filtration system to
remove particulates (inks and emul-
sion). Following the filtration step(s),
reclaimed solvent is typically reused.
Some systems have separate wash,
rinse, and air dry cycles or separate
tanks for washing and rinsing. Solvent
reservoirs must be replenished intermit-
tently and changed once or twice a
year. Filter wastes are typically dis-
posed of as hazardous waste.
Risk
Compared to manual application
of the traditional screen reclamation
chemicals, the DfE risk evaluation of
automatic screen washers found that
worker inhalation exposures to the
volatile organics used in solvents (min-
eral spirits and lacquer thinner) were
reduced by as much as 70 percent.
Although health risks associated with
dermal exposures to the chemicals
remained high, these risks could be
reduced dramatically if gloves are worn
while handling the screens. Since the
automatic screen washer is used for ink
removal only, the risks associated with
emulsion and haze removal remained
the same as the traditional system's
risks for these steps.
Performance
As described above, there are
several types of automatic screen wash-
ers, and for each type there are several
manufacturers. Because of the
resources required to do a full demon-
stration of the equipment commercially
available, performance demonstrations
of automatic screen washers were not
conducted as part of this project.
Cost
The DfE Screen Printing Project
estimated costs for two automatic
screen washers, assuming that the
washers were used for ink removal
only and that six screens (2,127 in2
each) were reclaimed per day. Screen
reclamation costs using an automatic
screen washer ranged from a low of
$4.13 to $10.14, compared
to $6.27 for traditional
reclamation. The
largest cost com-
ponent is typical-
ly equipment
cost. Additionally,
the savings of
switching to this tech-
nology would be greater if
this costing accounted for the labor
savings of workers moving on to other
tasks once the screen is loaded in the
washer. It is important to note that the
cost per screen of the more automat-
ed, higher-cost washer would be
much lower if it operated nearer to its
capacity of over 100 screens per day.
Sodium Bicarbonate
Spray
A sodium bicarbonate (baking
soda) spray technology was evaluated
by the DfE Screen Printing Project to
determine if it is potentially adaptable
as an alternative screen reclamation
technology. This technology is currently
used for removing coatings, such as
paint, grease, or teflon, from metal
parts. In these applications, the technol-
ogy has been successful in replacing
hazardous cleaning chemicals. Based
on the technology's success in other
applications, it appears to be a promis-
ing substitute for chemical screen recla-
mation systems. Because the sodium
bicarbonate spray technology had never
been tested for screen reclamation, DfE
staff conducted a one-day site visit to
the equipment manufacturer's facility.
Three imaged screens were inked with
three types of ink. An inked screen was
placed inside an enclosed cleaning
booth, and the screen was passed, back
and forth, under the sodium bicarbon-
ate spray. No chemicals other than the
sodium bicarbonate were used during
the reclamation.
Risk
The DfE project did not under-
take a risk assessment of this spray
technology for a number of reasons.
Sodium bicarbonate has been shown
to be a fairly innocuous chemical, and
it is not a skin irritant. In addition, it is
a common ingredient in baked goods,
toothpaste, and detergents. If this tech-
nology proves to be a viable alterna-
tive for screen reclamation in the
future, a detailed assessment of the
human health and environmental risk
should be conducted.
Performance
The performance demonstration
showed that cleaning the screen with a
pressurized sodium bicarbonate spray
alone, without water, resulted in exces-
sive damage to the screen. Performance
clearly improved when the sodium
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FOR
DRAFT
October 1994
bicarbonate spray was combined with a
pressurized water spray for screens with
solvent-based ink and water-based ink.
Typically, the emulsion came off in
stringy rolls, and ink flaked off rather
than dissolved. A 100 in2 area took
approximately 15 minutes to clean. Fol-
lowing this cleaning, there were either
significant haze or ink residue spots.
Slightly greater spray pressures or
slightly longer times resulted in visual
Sodium Bicarbonate Spray Enclosure
screen damage or a ripped screen.
Cleaning of UV-curable inks was inef-
fective. No evaluation of subsequent
use of these screens was made.
Based on these limited demon-
strations, initial results indicate that with
further testing and research, this may be
a promising new screen reclamation
technology. Some modifications are
needed to clean the screens faster and
with less possibility of screen damage.
For example, the physical support
behind the screen greatly reduced the
stress on the mesh. Use of hot water
was suggested as a means of improving
emulsion removal. Other modifications
may include decreasing the sodium
bicarbonate particle size, or modifying
the delivery rate and pressure of the
sodium bicarbonate and water sprays.
Further testing is needed before a defin-
itive evaluation of performance can be
given.
Cost
Since the available equipment
was not designed specifically for screen
reclamation, we have assumed that the
cost of equipment modified for screen
reclamation would be similar to the
cost of the equipment used in the per-
formance demonstration. The available
equipment ranges from $32,000 to
$52,000, including a filtration system.
The sodium bicarbonate itself costs
between $0.65 to $0.75 per pound,
based on amount purchased, and
approximately one pound is sprayed
per minute. If this technology proves to
be a feasible alternative for screen
reclamation after further development,
a more detailed cost analysis can be
conducted.
The Design for the
Environment
Approach
This case study describes three
distinct screen reclamation technologies
that could offer you the means to
reduce employee exposures to chemi-
cals. These technologies may also
reduce the total cost of screen reclama-
tion (which includes equipment, labor,
reclamation products, and waste dis-
posal costs). One of the technologies
under development (sodium bicarbon-
ate spray), offers the benefit of using
relatively benign chemicals.
The industry and EPA partici-
pants in the DfE Screen Printing Project
expect that the findings of this and
other case studies can be transferred to
screen printing operations throughout
the U.S. and abroad. The benefits these
technologies may offer include reduced
occupational exposures and risks,
fewer chemicals used for each screen
reclamation, and reduced time spent
on screen reclamation.
The EPA's Design for the Envi-
ronment Program encourages you to
evaluate systematically the technolo-
gies, practices, and procedures in your
facility that may impact the environ-
ment. Our goal in working with screen
printers is to help you to make more
informed choices, now and in the
future, by catalyzing the search for and
evaluation of cleaner alternatives. With
this case study and others like it, we
hope to illustrate the application of this
goal and the pursuit of continuous
environmental improvement. Through
these efforts, we hope to assist printers
in reducing pollution at its source.
For more information on the
technologies discussed here, contact
your equipment suppliers. For more
detailed information on other techno-
logical and chemical alternatives, see
the summary of the DfE Screen Printing
Project full technical report, entitled the
Cleaner Technologies Substitutes
Assessment (CTSA). Additional case
studies and other information products
summarizing the evaluation of screen
reclamation alternatives are also avail-
able. To obtain other case studies or
the draft Screen Reclamation CTSA,
contact:
U.S. EPA
National Center for Environmental Pub-
lications and Information (NCEPI)
P.O. Box 42419
Cincinnati, OH 45242-2419
Fax: 513-891-6685
For a trade association information,
please contact:
Screenprinting and Graphic Imaging
' Association International (SGIA)
10015 Main Street
Fairfax, VA 22031
Phone: 703-385-1335
dsX*1
For more informatiSn _
EPA's Design for the Environment Pro-
gram contact:
Pollution|Pr^ent^n Information
U.S.
410 M Street^W
Washington: DC ^ jyy. ,,.
Phonej 2UZ?260-1023::. : v
Fax: *
WIU \l,-"'-4
O^ Recycled/Recyclable
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Printed with Soy/ConoJa tnEon paper that contarns
at least 50% recycled fi
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