The term Rich Black refers to a mixture of inks containing the four process colors: cyan, magenta, yellow, and black (CMYK). It is necessary because no black ink is truly black, and the combination of the four inks will result in a denser black, or “rich black.” There are many recipes for rich black but after much testing and calibration, ProSource Printing has selected the CMYK breakdown that works best with our systems and presses:

Cyan: 30%, Magenta: 30%, Yellow: 30%, Black: 100%
Here is a simulated comparison of what it would look like with just black, and ProSource Printing’s Rich Black recipe:

We do not recommend using CMYK values higher than these. Using too much ink will cause the final print to be muddy, and will have a higher chance of smearing.