Process vs. Spot Printing
Process colors are reproduced by printing overlapping dots (halftone screens) of cyan (light blue), magenta (dark pink), and yellow inks (CMY) to simulate a large number of different colors. Since CMY inks are translucent, they absorb some colors and reflect others. To create blue, for example, you blend cyan dots and magenta dots. Your eyes merge the cyan and magenta dots to perceive the color blue. This process uses the white background of paper as the medium for creating the perception of color. For this reason in screen printing CDs, often a flood of white ink is used to coat the silver or gold disc before printing with the process inks. The white background helps insure that the colors remain true.
What about the "K" in CMYK? You could, in theory, mix 100% of cyan, magenta, and yellow to create black. However, you never print 100% of these inks for two reasons: First, ink pigments are imperfect and printing this combination of cyan, magenta and yellow creates muddy brown color instead of a sharp black. In addition, printing too much ink on a particular area of a page, or disc, can oversaturate that area causing the quality of the printing to deteriorate. To achieve fine detail and strong shadows in print, printers use black ink (K) along with cyan, magenta, and yellow inks. Now you've got CMYK.
Spot colors are printed with premixed inks on a printing press or screen printer. You may choose from among hundreds of different spot-color inks. Each spot color is reproduced using a single printing plate or screen. The Pantone Matching System (PMS) is only one of several popular spot color models used in printing. (dataDisc uses the PMS system) Each PMS number references a unique spot color and these colors can be found in a swatch chart. By using this type of numbering system, folks can communicate exact colors to each other without actually looking at the same samples.
It's important to remember that spot colors may not actually translate to matching process colors. Unlike process printing, which prints dots of the different colors, a spot color is printed at 100% is a solid color and has no dot pattern. A tint is a lightened spot color or process color and is created by printing smaller dots of the base color.