We've exposed our screens, dried them, and now we're ready to go to press.
Taking the time to properly prepare these screens before setup can save
time (and headaches) during your production run.
(Read the article Getting Started: The Screen)
Blocking Out the Screens
WHY: Screen filler, also known as blockout,
is an added protection from ink leaking through pinholes and that strip
of exposed fabric between the screen frame and the emulsion you’ve
applied. This liquid is inexpensive and can be purchased from most full
service suppliers.
HOW: Lay your exposed screen
on a table with the print side up. Pour a line of screen filler around
the perimeter of the screen, close to the edge of your emulsion. With a
square of cardboard or plastic (credit card size) spread the screen
filler to cover the exposed mesh between the edge of your emulsion and
the edge of your screen frame. Continue spreading the screen filler
inward, within an inch or so of the image area, to cover any discovered
or undiscovered pinholes.
Be careful not to cover up your
registration marks
with screen filler, assuming you will use these marks
when you register the screens on the press. You will tape over these
registration marks on the print side of the screen once the graphic is
lined up and you are ready to print the job.
Your technique will
be to lay down a thin layer of screen filler around your screen. Allow
the screen filler to dry on the screen completely. Drying should only
take a half hour in even the most humid of shops. You can place your
screens in front of a fan or in the open breeze of windows or your dock
door to speed up the process.
To save a little money, even though
screen filler/blockout is inexpensive, you can use your old emulsion.
Even when emulsion no longer works on screens for exposing, it will
still do the trick as a blockout product. Going the old emulsion route,
allow the screens to dry completely. For best results, set your screens
in the sun to harden this extra emulsion coat.
Taping Your Screens
WHY: To keep ink from leaking from the angle where the screen frame meets the mesh, we want to tape all four sides.
HOW: Lay your screen on a table, ink side up, just the way it will be loaded into the printer. With strips of tape
the same length as each side of your frame, tape the angle where the
mesh and screen frame meet. If you have not used screen filler, also
tape a strip around the edges of the mesh, between our taped corner and
the emulsion.
You can add another strip of tape around the frame
of your screen, especially top and bottom, to protect the frame from
ink.
This will speed up cleaning after the job is done. Be sure that no
wrinkles exist along the edge of the tape where ink will leak under and
eventually escape onto your garments. It’s always a good idea to burnish
down the tape edge that will come into contact with your squeegee to
assure no ink leaks under your tape.
Taping the ink side of you
screen should be all you need. No need to tape the print side under
normal circumstances. Some printers will tape inside the screen right up
to within an inch or so of the image. By doing this, you can pull the
tape at the end of the run and have less screen surface to clean. This
is a perfectly acceptable practice and a matter of personal preference.
When
taping over the emulsion to save clean up time, start from the top
(closest to you when the screen is set up on the press) and tape in
horizontal strips toward the bottom.
In this way, the squeegee
stroke will not cause the tape to roll up under the squeegee pressure.
(The overlap of the tape goes the direction of your print stroke.) If
you push your squeegee rather than pull, reverse this process and tape
from bottom to top.
(Read the article: The Manual Print Stroke)
Be sure your tape completely covers at the
corners where the tape strips meet. If necessary, add another short
piece of tape at the corner to ensure a tight seal against ink leaking.
Some
printers use
masking tape, but masking tends to breakdown during
production
and leave tape residue in your ink. Masking tape will also
tear in the seam between the frame and mesh due to squeegee pressure,
and
then leak ink around the sides of your screen. Better to use tape
that is specifically made for screen preparation.
Tapes made for
screen application are available from full service suppliers.
Most of
these tapes will have a solid blue or a checkerboard blue and white
strip along one edge. Where you see the blue or checkerboard strip,
there is little adhesive. The idea is to place the low adhesive portion
of the tape on your screen frame and the other side of the tape onto
your mesh. Over time, tape adhesive can build up on your screen frames
and become sticky and messy. The low adhesive strip along one edge of
the tape is made to reduce this buildup of adhesive.
When applying
any of these tapes using a tape gun, be careful that the cutting edge
of the tape gun does not tear the screen mesh. Most printers will pull
off a length of tape and apply by hand rather than using the tape gun to
directly apply to the screen.
During production, if you discover
pinholes or ink leaks, use tape to block the print side of your screen.
Masking tape will pick up ink from subsequent screens and during any
wiping of the screen and transfer the ink to your garment, so not a good
option. For larger areas, you can use your screen tape. For small
pinholes, especially close to the image area, use pieces of Scotch tape
to cover.
Much of our success in screen printing is in the prep
work, far more than in the actually printing of each garment. In most of
our shops, we have the printing part of production fairly well in hand.
It’s your prep work that separates one shop from the next.