When working on a design for print, you’re probably focused on colors, fonts, and layout. But behind the scenes, there’s another decision happening that can totally change how your colors behave on paper: knockout vs. overprint. These are two ways colors can interact when they overlap, and knowing the difference helps you avoid surprise results when your design goes to press.
A knockout removes the background color underneath an object so the top color prints directly on white paper (or whatever the base is). It’s like punching a hole through the bottom layer so only the top color prints there. For example, if you have black text on a red background. With knockout, the red doesn’t print behind the letters, the printer “knocks out” that red in the shape of the text. Then the black is printed directly on the paper. This gives you sharp, clean edges and true color.
Overprint means the top color prints on top of the color beneath it—without removing anything. Both inks are laid down, and they mix visually where they overlap. Using the same example (black text on a red background), if black is set to overprint, the red will still print behind it and the black will print on top. With black ink, this usually looks fine (and actually helps avoid misregistration). But with lighter or transparent inks, you could end up with an unexpected color where they mix.