Like we discussed in the previous post, trapping is a technique used in printing to prevent small gaps between colors when they’re printed next to each other. These gaps can happen because paper can shift slightly, or ink doesn’t land exactly where it’s supposed to. Trapping creates a tiny overlap between colors so that if things don’t line up perfectly, you won’t see an ugly white line. Think of it like cutting and pasting: if you’re gluing down a shape on top of another and you’re not sure it’ll land right, you make the bottom shape a little bigger, just in case.
Partial overlap is one specific way trapping is done. It means that one color is nudged slightly into another, but not fully covered—just enough to hide any misalignment. For example, imagine printing a blue circle on top of a yellow background. If the press is even a fraction of a millimeter off, you might see a sliver of white between them. With partial overlap, the blue might slightly “bleed” into the yellow area, creating a small buffer. It’s not noticeable to the eye, but it saves the final print from looking sloppy. Full overlaps can change the way colors look when mixed, especially with transparent inks. That can mess with the design. Partial overlap gives printers more control by having enough coverage to hide errors, but not so much that colors muddy or shift.