Printers and graphic designers often use rich black to create a deeper, darker black to achieve an even, very dark coloration for large areas of ink coverage. A standard rich black is composed of 100% process black laid over a screened percentage of a process color build.

Because it is composed of more than one process ink, misregistration of rich black on press is likely. Consequently, QuarkXPress handles trapping differently for rich black. If an object color spreads into a rich black background, all process colors except process black will spread according to the value specified in the Auto Amount field (Edit > Preferences > Trapping pane). If the rich black object color is being choked by a background color, then all process colors except for process black will choke. This special trapping process is used to keep the background process colors from showing through in the event of misregistration.