When creating or editing presets, the value you type for Black Color determines what is considered solid black and rich black. A rich black is any black color that uses a support screen—additional percentages of one or more process inks to strengthen the black.

The Black Color setting is useful when you must compensate for extreme dot gain (as when using low-grade paper stock). These situations cause black percentages lower than 100% to print as solid areas. By screening back blacks or rich blacks (using tints of solid black) and decreasing the Black Color setting from its default of 100%, you can compensate for dot gain and ensure that the trapping engine will apply the proper trap width and placement to black objects.

When a color reaches the Black Color value, the Black trap width value is applied to all abutting colors, and keepaway traps are applied to rich black areas using the Black trap width value.

If support screens extend all the way to the edge of a black area, any misregistration causes the edges of support screens to become visible, creating an unwanted halo or distorting the edges of objects. The trapping engine uses a keepaway, or a holdback, for rich blacks to keep support screens a specified distance away from edges of reversed-out or light elements in the foreground, so that the light elements retain their sharpness. You control the distance of support screens from the edges of black areas by specifying the Black trap width value.