A Cooperative Project
between the
U.S. Environmental
Protection Agency
and the
Printing Trade
 EPA 742-F-95-008
                                                                          SCREEN PRINTING PROJECT BULLETIN 1

                                   SCREEN  PRINTING
                             TECHNOLOGY ALTERNATIVES
                              FOR SCREEN RECLAMATION
                                   The screen reclamation process can be
                                   one of the most hazardous operations
                                   in a screen printing facility. Typically,
                              highly volatile solvents are used which may
                              be hazardous to the health of employees if
                              inhaled, ingested, or absorbed through the
                              skin. These products may also be hazardous
                              to the environment if they are not disposed of
                              properly. Traditionally, when reclaiming
                              screens, employees vigorously scrub the
                              screens in a wash-out  booth, with their  faces
                              close to the reclamation chemicals. This
                              increases the likelihood that they will inhale
                              the chemical vapors.

                                   To reduce the hazards of screen  recla-
                              mation to workers and to the environment,
                              screen printers can  use alternative tech-
                              niques for screen reclamation. These tech-
                              nologies help to reduce the employee
                              exposure to hazardous chemical vapors
                              either by speeding up the reclamation
                              process, or by enclosing the process, or by
                              eliminating the use  of volatile solvents.
          The DfE Screen Printing Project identifies
     several potential substitute technologies that
     can be environmentally safer than traditional
     screen reclamation, including: high pressure
     water blasters, automatic screen washers, sodi-
     um bicarbonate spray, media blasting, pulse
     light energy technologies, stripping technolo-
     gies, and emulsion chemistry. This bulletin
     highlights three of these technologies:
       •   High pressure screen washers
       •   Automatic screen washers
       •   Sodium bicarbonate  (baking soda) spray
          High pressure screen washers and auto-
     matic screen washers are  two commercially
     available technologies that can reduce a facili-
     ty's usage of traditional solvent-based ink
     removers. Sodium bicarbonate spray is a tech-
     nology now under development that could
     further reduce the costs and potential health
     risks of screen reclamation. This bulletin pro-
     vides comparative cost, performance and risk
     information for these reclamation technologies,
     when available.
          It should be noted that these technolo-
     gies were evaluated using a case study
     approach; these were not rigorous, scientific
     investigations. Instead, much of the informa-
     tion presented here is based on printers'  opin-
     ions of these technologies as they are used in
     production. This bulletin  compares the alter-
     native screen reclamation techniques to manu-
     al application and scrubbing of traditional
     screen reclamation chemicals. The traditional
     system used in the comparison consists of:
     lacquer thinner as the ink remover, a sodium
     periodate solution as the  emulsion remover,
     and a xylene/acetone/mineral spirits/cyclo-
     hexanone blend as the haze remover. These
     chemicals were selected because screen print-
     ers  indicated they were commonly used in
     screen reclamation.

High Pressure Screen  Washers

     High-pressure screen washers reclaim screens using
pressurized water, usually in conjunction with some reclama-
tion chemicals. Typically, 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,
usually for from ten seconds to one minute. The ink and  sten-
cil are then removed with 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 necessary, 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, in the systems evaluated, the emulsion and haze
removal products were formulated to allow discharge to
sewers. Where ink residues in the rinse water exceed waste-
water permit concentration limits, such as for suspended
solids,  manufacturers also supply a variety of filters. The
greatest environmental benefits are realized for systems
using improved filtration systems which allow rinse water to
be reused. Filter wastes are typically disposed of as haz-
ardous waste.
                  High Pressure Washer
     In general, the benefits of high pressure washers are
that they reduce both chemical use (eliminating ink
removers)  and worker exposure  (less scrubbing required).
The DfE Screen Printing Project found that the occupational
risks of this system were notably lower than the risks associ-
ated with the manual application of 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 organic solvents,
were significant. For the high pressure screen reclamation sys-
tem, health concerns were related to unprotected skin contact
with the reclamation chemicals. Dermal exposures could be
reduced dramatically, however, by wearing gloves.
     Switching to this type of screen reclamation technology
can reduce both your facility's releases of hazardous materials
and your regulatory burden by reducing the amount of clean-
ing solvents you use.  Contact your state and local regulatory
authorities for information specific to your location.


     Performance of a high pressure water blaster was evalu-
ated by DfE staff at a volunteer printing facility where the
technology was in place. Overall, the high-pressure screen
washer reclaimed the screen efficiently and effectively. When
demonstrated on screens with solvent-based, water-based
inks, or UV-curable inks, the stencil dissolved easily, leaving
no emulsion residue. Ink stains on these screens were com-
pletely removed by the haze remover even before the waiting
period or pressure wash.


     The DfE Screen Printing Project also estimated the cost
of equipment, labor, and chemicals for the high pressure
           wash. Assuming that 6 screens are reclaimed
               daily and each screen is 15 ft2 in size, the
                 cost estimate for the high pressure washer
                  totaled  $4.53  per screen reclamation. This
                  estimate was  compared to that of the tra-
                 ditional screen reclamation system (using
                lacquer thinner, sodium periodate, and a
               solvent blend). Using the same assumptions,
the estimated reclamation cost of 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 pressure  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, or mainte-
nance and operating costs which may also 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 exposures. The DfE Screen Printing Project
identified a wide variety of automatic screen washers on
                Automatic Screen Washer

the market and found significant differences in the chemi-
cals used and costs. Costs vary based on the level of
automation (such as conveyors), system capacity, and com-
plexity 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 spirits, are often recommended because of their effi-
cacy. There are, however, a number of alternative formula-
tions offered by equipment  manufacturers. Used solvent
drains off the screen and is directed to a filtration system to
remove particulates (inks and emulsion).  Following the filtra-
tion step(s), reclaimed solvent is typically reused. Some sys-
tems have separate wash, rinse, and air dry cycles or separate
tanks for washing and rinsing. Solvent reservoirs must be
replenished intermittently and changed once or twice a year.
Filter wastes are typically disposed of as hazardous waste.


     Compared to manual  application of the traditional
screen reclamation chemicals, the DfE risk evaluation of
automatic screen washers found that worker inhalation expo-
sures to the volatile organics used in solvents (mineral spirits
and lacquer thinner) were reduced  by as much as 70 per-
cent. Although the health risks associated with skin  contact
of the chemicals remained high, these risks could virtually be
eliminated if gloves are worn while handling the screens.
Since the automatic screen washer evaluated was 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.


     As described above, there are several types of automat-
ic screen washers, and for each type there are several manu-
facturers. Because of the resources required to do a full
demonstration of all the equipment  that is commercially avail-
able, performance demonstrations of automatic screen wash-
ers were not conducted in this  project.


     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  (15 ft2 each)
were reclaimed per day. Screen reclamation costs using an
automatic screen washer ranged from $4.13 to  $10.14 per
screen compared to $6.27 for traditional reclamation. The
largest cost component, and the cause of the variability in
costs, is typically equipment cost. For many print shops, espe-
cially higher volume printers, the equipment pays for itself
through savings in reduced chemical use. Additionally, the
savings of switching to this technology would be greater if
this costing accounted for the labor savings of workers mov-
ing 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
automated, 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 deter-
mine 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 technology has been
successful in replacing hazardous cleaning chemicals. Based
on the  success of the sodium bicarbonate spray in other
applications, it appears to be a promising substitute for
chemical screen reclamation 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. Each inked
screen  was individually placed inside an enclosed cleaning
booth,  and the screen was passed, back and forth, under the
           Sodium Bicarbonate Spray Enclosure

sodium bicarbonate spray. No chemicals other than the sodi-
um bicarbonate were used during the reclamation.


     The DfE project did not undertake a risk assessment of
this spray technology for a number of reasons. Sodium bicar-
bonate has been shown to be a fairly innocuous chemical
and it is not a skin irritant. In addition, it is a common ingre-
dient in baked goods, toothpaste and detergents. If this tech-
nology proves to be a viable alternative for screen
reclamation in the future,  a detailed assessment  of the human
health and environmental risk should be conducted.


     Several different methods for screen reclamation with
the pressurized sodium bicarbonate spray were demonstrated.
Performance was best when the sodium bicarbonate spray
was delivered through a pressurized water spray. 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. Following this cleaning, haze or ink residue
spots remained. Cleaning of UV-curable inks was ineffective.
No evaluation of subsequent use of these screens was made.

      Based on these limited demonstrations, initial results
indicate that with further testing and research, this may devel-
op into a promising new screen reclamation technology.
Modifications are needed to reduced  the cleaning time
required for  reclamation and to reduce  the 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 definitive evaluation
of performance can be given.


     Since the available equipment was not designed specifi-
cally for screen reclamation, it was assumed that the cost of
equipment modified for screen  reclamation would be similar
to the cost of the equipment used in the performance demon-
stration. The cost of 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 feasi-
ble alternative for screen reclamation after further develop-
ments, a more detailed cost analysis can be conducted.
          What is the Design for the
  Environment Screen Printing Project?

      U.S. Environmental Protection Agency's (EPA)
 Design for the Environment (DfE) Screen Printing Project is
 a voluntary project that encourages printers to consider
 environmental concerns along with cost and performance
 when purchasing materials. Replacing hazardous chemicals
 with environmentally-safer substitutes is one way to reduce
 the impact of printing on the  environment while maintain-
 ing product quality. Many printers, however,  may not have
 the time to identify and test environmentally-safer substi-

      That's where DfE fills the gap. EPA has teamed up
 with screen printing  industry representatives (including
 trade associations, printers, and suppliers) in the DfE
 Screen  Printing Project. The Project's goal is to evaluate
 and publicize pollution prevention opportunities in screen
 printing, particularly  in the screen reclamation process.
For More Information...
      For more information on the technologies discussed
here, contact your equipment suppliers. For more detailed
information on other technological and chemical alternatives,
see the summary booklet, Designing Solutions for Screen
Printers — An Evaluation of Screen Reclamation Systems.
Additional bulletins are also available.

   Pollution Prevention Information Clearinghouse (PPIC)
           U.S. Environmental Protection Agency
                 401 M Street, SW (7409)
                 Washington, DC 20460
                Telephone: 202-260-1023
                    Fax: 202-260-4659
                                                            Screenprinting and Graphic Imaging Association International
                                                                                10015 Main Street
                                                                                Fairfax, VA 22031
                                                                            Telephone: 703-385-1335
                                                                                Fax: 703-273-2870

                                                            You may also contact the DfE Home Page at:
                                                            http://www.epa.gov/dfe/ or the SGIA
                                                            Home Page at http://www.sgia.org/

                                                                 Printed with Soy/Canola Ink on paper containing at
                                                                 least 50% recycled fiber.