Trapping

Trapping builds a small, intentional overlap into artwork wherever two colors touch, typically a fraction of a point to a couple hundredths of an inch, so the edges of adjacent ink layers physically overlap instead of butting exactly edge to edge. Since no screen press holds perfect registration shirt after shirt, that sliver of overlap absorbs the drift and keeps one color from pulling away from its neighbor mid-run.

For a buyer, trapping is invisible when it works — it's the reason a two-color logo with a black outline around a red fill still looks clean on shirt three hundred of a run, not just shirt one off the press. We've watched an un-trapped file print beautifully for the first fifty pieces, then start showing a hairline of bare shirt between the outline and the fill once the screens drifted, a fix that trapping would have prevented from the first pull.

Pros build trapping into the separation before burning screens, sizing the overlap to the press's typical registration tolerance and the ink's opacity — too little and gaps show under normal drift, too much and dark trap lines peek out from under lighter colors. Fine detail and small text need tighter trapping discipline than a bold, simple two-color chest logo.

Buyers sometimes assume any visible gap between colors on a finished shirt is a printing mistake on press, when it's often a prepress trapping problem baked into the file before it ever reached a screen. Catching it at the art stage costs nothing; catching it after three hundred shirts are printed costs a reprint.