Does the term CMYK throw you for a loop? It refers to the four colors used in printing: Cyan, magenta, yellow and black. It is “subtractive” color, as it starts with white and ends with black as more color is added.
RGB color is composed of blue, green and red and is “additive” color, since it starts with black and ends with white as more color is added. RBG uses light to convey color, while CMYK uses ink.
These differing processes mean that an RGB color does not have an exact conversion to a CMYK color. So while RBG black (R0 B0 G0), looks great on a computer monitor, it looks very gray and washed-out when printed on paper.
Just using the black channel of CMYK (C0 M0 Y0 K100) also produces a gray-black on paper. While “true” black’s use is adequate for text color, it often doesn’t suffice for large sections of black.
To deal with the issue of washed-out blacks, a “rich” CMYK black can be created that contains percentage amounts of cyan, magenta and yellow in addition to the black channel. This creates a more intense black than using black alone. “Designer” black (C70 M50 Y30 K100), for example, is a favorite because of its vividness and beautiful tone on paper.
There are limits however to the percentage amount of ink that can be put down on the paper. In the printing process, print shops use a TIC (Total Ink Color) limit. This can range from 240%-340% of the CMYK channels.
Speed of the press, coating of the paper and type of printing process all play a part in determining the TIC limit. Be sure to consult your printer on the TIC limit they would recommend to get the best black for your print job.