How to separate colors for screen printing, step by step

Six steps

1. Say the physical size.Not pixels, millimetres, at the size it will print. Everything downstream depends on it: whether a thin line holds, what line count makes sense, how big the film is. The same file at 90 mm and at 300 mm is two different jobs.
2. Decide how many inks.This is a decision, not an outcome. Every ink is a screen, a pass and a registration of its own. Start from what your press lays down in one pass.
3. Choose the palette.The automatic pick gives you a starting point taken from the artwork itself. Then edit by hand: set the exact Pantone the client asked for, drop the ink covering one and a half per cent, merge three close reds into one.
4. Decide about the underbase.A light garment does not need one: white on white shows nothing and costs a screen and a pass. On a dark one, colors go dull without it, because the cloth shows through the film of ink.
5. Set the halftone.Line count, angles and dot shape. Take the line count from what your mesh actually holds, not from what looks better on a monitor.
6. Check, then export.Thin lines, narrow gaps, isolated pixels. Read the artwork rather than a list: the trouble spots are painted onto the image itself.

Why the size comes first

A minimum line is measured in millimetres, not pixels. Until the software knows what size this prints at, it cannot say a word about whether the mesh will hold that line. A customer’s file is almost never at print size.

The same goes for the line count. At 80 LPI the halftone cell is 0.318 mm across. Nothing thinner than a cell can survive as a shape: it becomes one dot or none. Until you have named the size, you do not know what in the artwork is thinner than that.

Why the ink count comes second

Because it sets both the price of the job and its risk. On eight inks any misregistration shows far more than on three, and every screen is money.

And because the palette is chosen to fit that number. Picking seven inks and then cutting to three is not the same as looking for the best three from the start: the first gives you the three strongest of seven, not the three best in the artwork.

What usually goes wrong

• A scan instead of flat artwork. A scan carries paper grain, and grain becomes tone. Each plate ends up with hundreds of fragments the mesh cannot hold. Drop the specks before you halftone.
• Fine text through a screen. Letters thinner than the halftone cell fall apart. If they are solid in the artwork, they should stay solid on the film.
• Two inks that are nearly the same. Two close reds instead of one is an extra screen, an extra pass and an extra registration risk, for a difference nobody sees on fabric.
• An underbase out of habit. On a white shirt a white underbase does nothing except cost a screen.

FAQ