Using Photoshop or Illustrator to make Separations
You now know how screen printing works, and you've learned that it takes a film positive to expose the photo-stencil for the screen.
At right you see the film scenario -- in order to produce two screens, one for each color.
While there are many, many various opinions on how to produce color separations for "flat-color" printing, this is the most basic and foolproof. It works in any software program that will produce a good black print -- and has layers for creating the art. Many authors and authorities will lead you through some highly complicated processes -- those work too -- but this method is most like the original method and really is the easiest.
What is the best film to use? Let me say first that your very best and most detailed reproduction will be Orthographic film processed by a printing firm or service bureau. This will give you superb results from even the most detailed images, including photographs, art, halftones and screen tints. The next best material is laser compatible film such as that used for making overhead projection cells. The LEAST desirable material is "vellum" which is translucent printing paper similar to tracing paper. This is used by amateurs, schools and some hobbyists who aren't too concerned about the fidelity or accuracy of their prints.
Art must be 100% opaque on the film! If you laser print has spots or translucent areas, these will allow light to leak through and spoil the print. Holes or "thin" areas in the laser toner should be touched up with an Opaque touch-up. (You can purchase "opaquing pens" at various art supply stores.)
Ink Jet printers are NOT recommended due to the translucency of the inks. You must have 100% blockage of the exposure light for the duration of the exposure.
Create the art -- each color on a layer
Set up Illustrator or Photoshop to the size of the final print. This print fits nicely on an 8.5 x 11 sheet, at 300 ppi.
Produce the art as you normally would. Use as many layers as you wish. Colorize the art as you wish. Make sure everything fits, and where colors meet (butt) allow the darkest colors to overlap the lighter colors a pixel or two. (This is called "trapping")
Registration: In this example, you see I've even included my own "registration" marks. These will actually be "burned" to the stencil, to align the art properly so the colors "register" or match perfectly. I cover them with some tape just before putting ink on the screen. NONE of the software produces an acceptable registration mark for screen printing.
This is a simple grid. The grid is on the black printer, and the blocks that fill the holes in the grid are on the red printer. I've pulled thousands of prints with these and they've never let me down -- even printing up to seven colors!
Finish your art, print and proof as you wish and get everything perfect. Now you're ready to create separations.
This is so obvious and simple, I'm a bit embarrassed to even be writing a tutorial about it.
Ready to Print: Before printing, you should change the color of each "color" layer to black. Many black-only laser printers will screen colors when printed. You don't want that. The image to print from each film must be 100% BLACK and OPAQUE.
Now, simply turn OFF all layers except the one you wish to print. Issue the PRINT command and print. Photoshop or Illustrator will print the film of that layer only.
Now, turn that layer off and turn on the next layer for printing. In this fashion, you're producing your own separations -- and you KNOW they'll work, beautifully. Once they're all printed, tape them to a window (or your light table) one by one, in registration, to proof the film. Now, you're ready to make screens.
Use Print with "Preview": The Print with Preview function in Photoshop is well worth the trouble. Illustrator's print command defaults to a Print with Preview mode anyway. Using these, you will see a thumbnail of how the actual print will look. You can check and make sure everything is okay before you initiate printing.
Ready to Burn some Screens: With all the films in hand, fully proofed on the light table, you're ready to burn your screens and get some printing done. I recommend you burn ALL screens for a job at the same session. If you wait until later to burn and develop the next color screen, atmospheric conditions such as humidity may cause the finished screen to go "out of registration" -- if you do them all at the same time, they'll all be uniform.
I could have led you down the path to automated separations, spot colors, channels, duotones -- all of which work -- but why go the extra work and agrivation when you don't have to? Here's one I just finished. Notice it's on a black shirt, so WHITE was my second color instead of black.
These steps work for ANY project where you are separating FLAT colors, not process colors. You can also produce separations for decals, signs, and even litho printing projects like newspaper ads, business cards, etc. It's simple, direct, and takes the LEAST amount of time.
I guarantee it!
Editor / Publisher: Photoshop Tips & Tricks, DTG Magazine.
P.S. : If you've got great designs and you want to get articles printed -- but don't want the mess and fuss of screen printing, get yourself a CafePress account and let THEM do the work!
