Screen Printing Tutorial

A guide for printing signs with volunteer labor, optimized for the Liberty L logo

Prototype two color procedure for signs for 2008 precinct conventions

Equipment List

  • 22 inch stretcher panels
  • Screen Printing screen (plastic monofilament weave, not silk)
  • Chemicals: Emulsion, sensitizer, remover
  • Screen filler or nail polish to fill holes with in problem parts of cured screen
  • Needle to force holes in problem parts of cured screen
  • Heavy duty staple gun (T-50 or similar recommended) and staples
  • Squeegee
  • Transparencies for signs (this may need a procedure page or tutorial of its own)
  • Spacer (posterboard or card stock cut to separate 2.75 inches vertical and horizontal)
  • Crystal clear adhesive tape
  • Black electrical tape, preferably 1 inch wide or wider if such can be found
  • 500 Watt halogen lamp or similar light source
  • Water hose, air compressor with splay attachment, or equivalent
  • Screen printing ink -- dark blue and dark red recommended
  • Foam Brushes
  • Whatever I forgot to list here.  This tutorial may get reworked sometime.

Prepare the screen

the frame

Snap together the 22 inch stretcher panels into a square frame.

stapling mesh to frame

Tightly and evenly staple the mesh to the screen.  Use staples instead of brads or nails -- staples can be removed in the future without damaging the frame or screen.


applying emulsion

Apply sensitized emulsion to the screen and scrape off excess with a squeegee.  Try to keep it even and minimize any visible holes.

Allow to dry for a couple of hours.

spacer for aligning transparency

After it's dry, use a spacer to clarify 2 and 3/4 inches away from the outside edge of the frame (some preexisting transparencies may need a horizontal adjustment from this).


taped transparency.  removed the spacer to finish taping

Tape the transparency to the outside of the screen -- horizontally flipped -- using crystal clear transparent tape (translucent "magic" tape may not be as good). 


500W halogen lamp   exposed

Expose to a halogen lamp until the exposed sensitized emulsion turns darker and green.  IMPORTANT: ensure that light does not backscatter and expose the rest of it as well!  Carefully remove tape and transparency.  Store transparency for possible future use (such as if something goes irreparably wrong or a screen is ruined and a replacement is needed).


washing off underexposed emulsion

Wash off the underexposed emulsion.  How much pressure or abrasiveness we can get away with using may require some experimentation.  A superseded Speedball emulsion was able to take a full blast of water spray from an air compressor attachment, while a water hose attachment on a later occasion and a different emulsion was able to blast the needed emulsion off of the screen, effectively destroying it.


looking for troubles to fix

Inspect the screen for excess emulsion and holes that require attention.  Punch holes with a needle or push-pin as needed when adequate control with a water spray can't remove the excess.

Some documentation suggests leaving the finished screen to sunlight or halogen light to further cure it to reduce risk of future damage.  Allow screen to completely dry.  Fill in holes with a filler.


applying tape  taped front  taped inside to frame

When finally dry, apply black electrical tape or a suitable inkproofing substitute to the outer edges of the frame.  The front of the screen that will be contacting the sign blanks is what counts -- tape as needed to secure the tape on the others side to the wood frame.


Using the screen

blank template  positioning to ink

With standardized positioning, the locations relative to the sign blanks should be consistent across messages.  Place the sign blank in its indicated position and the message or template screen in its indicated position.  In this example, the template image was applied previously, and the message for Dagney Taggart for Railroad Commissioner is being applied.


using the screen to print

With an inked foam brush, spread a thin layer of ink either right-to-left or left-to-right.  Avoid alternating directions while inking the same screen blank.  Try to cover all portions, especially the notices required by statutes, but do not apply the ink with excessive thickness.


printed

Quickly remove the screen from the blank.  The screen will be sticking to the sign blank, so be careful to cleanly separate them.  Hand the sign to someone who can place it in a drying space location or place it in a safe location in arm's reach to be placed in its drying location after you run out of such locations in arm's reach and have several signs to relocate.  Avoid changing mental gears.  It's time to start the next sign.


printing again

Check that there isn't ink on the wrong side of the screen and remove any stray amounts with a paper towel or if that won't work, a damp paper towel, then try the area thoroughly before resuming.  If it becomes necessary to wash the entire screen, you are finished using that screen for the day.  Have additional dry screens you can use when this happens.  Position next sign blank or template place the screen, and ink the next sign.  Repeat as appropriate or until screen needs to be cleaned, in which case move on to the next screen.


Don't List


Been here; Done this; You may want to avoid it.

Use too much ink or thinner ink to reduce the pinstriping effect

Ink will instead run through the recessed lines and produce an unusable sign

Print using a squeegee

Ink will likely run through the recessed lines if you can't do it in one swipe -- and you probably can't.

Spend extra time to ensure the sign is printed correctly

Ink will run through the recessed lines this way too.  It loves to do this -- don't give it the chance.

Forget rinsing off that screen

The ink will cure and render the screen permanently unusable

Lean the screen against a wall while exposing it

The light will backscatter curing everything, leaving the screen unusable

Use a spraybottle to remove excess emulsion after curing

The human hand wasn't built for the punishment this procedure dishes out


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