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| August 2005 issue of PRINTWEAR |
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Tips
and Tricks for the Textile Screen Printer
by Douglas Grigar, Master
Screen Printer
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(A version of this article originally appeared
in the August 2005 issue of PRINTWEAR.)
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We all love cheap tricks and simple ways
to make our lives easier. We might define a tip as a small change in
a normal procedure that saves time or supplies or makes something easier,
while a trick would be something that we may not have even thought of,
but when employed, makes things simpler or makes the work smoother,
shorter, or is just too cool to pass up.
The common thread with tips and trucks
is that they are simple and cheap; we all love simplicity, and good
things that are cheap are a definite windfall. I have collected a few
of my favorites for this article - simple things that cost little or
nothing, but are just too helpful to keep under my hat. Old timers who
may know of these things should still look them over; you may find one
you’ve not seen before. Here are some simple ways to make the
life of screen printing better.
The Tips
Let’s start with a few ideas, moving
from art into production, little suggestions that can help things run
smoother, better, and even faster.
Exposing information onto the
screen - In art preparation, while making positives, make
sure you print out the information as needed for each screen onto the
positives, then expose that information onto the screens (see Figure
1). With information such as color, mesh, print order, and job name/number,
a misplaced screen will be easily identified and moved to the proper
press for production. Additionally, if the number of screens/colors
are noted on each positive along with the print placement - exposed
onto the screens in the correct position and direction - a screen- or
print-department worker will know if a necessary screen is missing.
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[Figure 1: Actually exposing critical
information onto a screen - by means of incorporating the information
onto the film positive’s margin - is a great enhancement to communication.]
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Keep that bucket clean
- Emulsion buckets are best kept clean and covered. If contamination falls
into the emulsion, there’s a good chance it will end up on the screen,
most likely just where you need a dot to form. Always keep the lid over
the emulsion when coating, if only to keep the dust out. Wipe the lip
of the emulsion after pouring emulsion into the coater. When emulsion
dries on the lip and the lid, when opening the bucket, dried emulsion
becomes a contaminant and will most always fall into the liquid emulsion
when peeling the lid from the bucket. Dried emulsion on the lip of the
bucket is often called “crusties” - not a pleasant name, but
appropriate for this soon-to-be contaminant floating in the emulsion.
Condiments or quick-refill
tools? - Kitchen- or restaurant-style ketchup (mustard,
mayo, honey, and so on) squeeze bottles are great for keeping your trough-coater
filled (and crusties off the emulsion bucket) as often as needed (see
Figure 2). Continue to wipe the side of the emulsion bucket so you can
dispense emulsion more easily and uniformly. Keeping the level as consistent
as possible while using a coater will keep the layer of emulsion on the
screens more consistent. When using a squeeze bottle, it is best to use
a bottle that is new - not used for other products - and washed with degreaser,
rinsed, and dried before filling with emulsion (squeeze bottles like the
one pictured can be found at some supermarkets, home improvement stores,
and/or home-and-bath stores). To keep extra bubbles out of the emulsion
you squirt into the trough-coater, squeeze slowly and store the bottle
in a black bucket with the nozzle pointed down to keep the air pocket
trapped at the squeeze bottle’s bottom.
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[Figure 2: Hold the pickles, hold the
lettuce…But do use various kitchen tools to facilitate the handling
and application of liquid emulsion.]
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Don’t miss the bottom of
the bucket! - Ever wonder why some screens just don’t
work as well as they should? Have you ever considered that some screens
coated from the bottom (or the top) of the bucket of the emulsion were
coated with emulsion that was not mixed correctly? To help prevent having
some unmixed emulsion lurking at the bottom edges of the bucket, try doing
your mix in a second clean bucket. Save an empty bucket, clean with degreaser,
rinse, dry, and reserve for mixing emulsion. Pour your sensitizer into
the second bucket, then add the unmixed emulsion into that second bucket
while stirring. Make sure you scrape the last of the emulsion from the
first bucket into the second bucket to get the last of the unmixed emulsion
out and mixed completely.
Swiping
kitchen tools? - The simple kitchen spatula is a great tool
to scrape emulsion and keep your fingers out of the product, preventing
contamination in the emulsion and exposure to diazo (as shown in Figure
2). A clean plastic kitchen spatula is also a great tool for scraping
emulsion out of a trough-coater and for mixing emulsion in the bucket.
I suggest buying a new spatula, though, as swiping kitchen tools is a
recipe for domestic squabbles.
Three tips for getting the mixture
exact and not making a mess - Mixing dual-care and diazo
emulsion requires mixing the small container of diazo with room-temperature
water. However, tap water from the faucet can often contain chemicals
and minerals that can affect the emulsion. The first
of the three tips, therefore, is to have distilled water (no, not that
nice, bottled water that costs more than gasoline; distilled
water) on hand to mix with the diazo. Distilled water (available at the
grocery store) is cheap and will not contain contaminates that will change
your emulsion’s properties. The second tip is to
head for your local scientific/medical supply house for a large syringe
(without the needle) or a graduated chemical-measuring vial, to assure
that you use the exact amount of water for mixing the diazo each time
you prepare the emulsion. The third tip is, when mixing
the diazo in its little bottle, to wrap a rag around the bottle before
shaking to prevent any seeping liquid from splattering everything in sight.
The rag is also useful - when checking under the cap for spots that will
tell you that the mixture has not sufficiently dissolved in the water
- to keep the diazo-water off your hands and clothing.
Two coating tips
- First, consider making a screen-holding jig to allow
you to coat two-handed. The jig keeps the screen safe while coating, frees
up your holding hand, and coating two-handed will most often produce a
more even coating of emulsion and allow the coater to apply more pressure
to the mesh while coating. Second, if you are in a rush
after coating a screen, fill a bucket (that is large enough to hold your
trough-coater) with water and just drop the scoop coater in the bucket;
the water will keep the emulsion soft and easy to rinse off when you get
a chance to get back to cleaning. This frees you to continue other tasks
while preventing hardened emulsion from forming a crust (yeah, crusties)
that is difficult to remove when dry.
Tricks with tape
- The first trick is simply the application of a good but inexpensive
two- to three-inch clear packing tape to the inside edge of the squeegee
where the squeegee rubber meets the handle (see Figure 3). Place the tape
on the squeegee blade and push it into position against the handle with
your fingernails, in order to seal the crack between blade and handle.
The tape will prevent ink from seeping under the handle and warping the
blade via chemical action, and can be pulled off the squeegee after a
quick wipe-cleaning with a rag. This is simple, cheap, and prevents undue
contact of the squeegee with chemicals.
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[Figure 3: A strip of tape sealing
the gap between squeegee blade and holder will prolong the blade’s
useful existence.]
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| THE tape trick
- The final segment of this collection of tips and tricks is my hands-down
favorite. It never fails to get a jaw-dropping response the first time
people see or use it. In fact, many refer to it as “the
tape trick.” I offer instructions below, with the single caveat
that it will take you longer to read than it actually takes to perform.
Here are the steps:
• Have the screens prepared and made
ready for the print-registration process (this trick is only necessary
to align multiple colors that need tight registration).
• Move the micro registration to neutral
(or zero) on the press. This step is important because without enough
latitude movement in the micro settings, screens may have to be loosened
in the press clamps and moved, resulting in lost time.
• Align the screen-registration marks
to your standard platen markings, or place into your plate registration
jigs or pins (part of your pin-registration system) (see Figure 4).
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[Figure 4: When performing “the
tape trick”, align the screen-registration marks to your standard
platen markings. Then…]
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| • Decide what color is the
“main” color for the registration “baseline”; choose
an outline, underlay, or other element that has a large amount of contact
with all the other colors in the design. Once this screen is aligned in
the press clamps, tighten everything and never move this color. Only move
other screens to align with this baseline (if you move the base color, all
the others will be out of alignment).
• Choose a platen-covering rag that
has a large color or tone contrast to the main color. Contrast must be
sufficient to view the print through each coated screen. For example:
if the print is black, use a white rag; if it is white, use a black rag.
Make sure to use liberal amounts of platen adhesive, flatten, and press
well to the platen to keep the rag from moving while you are using it
to align the colors.
• Cover the print with clear packing
tape. Overlap the edges to prevent ink transfer to the rag under the tape
(see Figure 5). The print should be visible as if there was nothing covering
the image. Do not flash the image. Flashing could cause shrinkage and
one of the points of this trick is avoiding shrinking to get accurate
registration.
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[Figure 5: …Cover the print with
clear packing tape, overlapping the edges to prevent ink transfer to
the rag under the tape. Then…]
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• Looking past the mesh
and emulsion layer, align the images from the other screens with the press
micro registration (see Figure 6). Fill the screens with ink when you
are satisfied they are in position.
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[Figure 6: …Sighting past the
mesh and emulsion layer, align the images from the other screens with
the press micro registration. Then…]
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• Start the small micro adjustments
needed after each color is printed directly onto the tape with a rag.
Following each color, ink can be wiped from the clear packing tape with
an additional rag (slightly moistening the rag with press-wash helps).
This print-and-wiping procedure can be repeated as often as needed (see
Figure 7).
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[Figure 7: …After each successive
color’s registration, wipe the clear packing tape clean (with
a rage slightly moistened with press-wash) and move to the next color.]
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| • Lock the micro registration
after each color is aligned. Make sure you pull the screen up out of the
arm locks and return to check that you did not inadvertently put pressure
on the screen, creating a false registration. The job is now ready for production.
Often, the act of aligning the print with standard markings on your platen
will leave the job ready to print, and the tape trick will verify this condition.
A printer’s registration procedure saves time, rags, and forces the
standardization of art, screens, and production.
Share Your Tips
I hope you find at least one of my tips and
tricks useful, and that many hours of your time are saved while your processes
move more smoothly. This is a short list of my current favorites. I’d
like to add more to my list, though, and present them in a future article.
If you have a tip or trick to which you’re partial, be sure to send
your suggestion to me. You may be able to share your favorite trick in
a future Grendel article.
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