The process color separation method require one cyan, one magenta, one yellow and one black screen.
Before print production begins, screen printers must use image manipulation software or older analog methods to convert an original image into separations. Each separation represents one color of ink to be screened. Different screen printing methods require different separation schemes, depending on the combination of colored inks the printer plans to use. Common screen printing color separation methods include process color, simulated process color and spot color.
Process Color
Process color screen printing separation uses four separate color screens and four transparent inks: cyan, magenta, yellow and black. Process color is also known as CMYK, an acronym for the four colors of ink with "K" representing black. The printer makes four passes and applies a thin screen of each of the four inks to the destination medium. The four single-color inks blend together to create the final image. Different combinations of densities of the inks create different colors in the full-color silkscreen print. Offset printers also use process color to print publications. Process color separations work best with light or white destination media. Darker colors may show through from behind the ink.
Simulated Process Color
The simulated process color for screen printing separations uses up to eight color separations and eight standard inks instead of four (as with CMYK). Simulated process color separation requires more materials than process color. Because simulated process color inks have a greater opacity than process color inks, simulated process color separations can produce a much narrower range of colors when blended. Simulated process color is also known as multichannel color. What simulated process color lacks in range it makes up for in stability. Unlike process color separations, simulated process color can be used confidently with dark-colored destination media.
Spot Color
Typically, spot colors are specific colors found in an original image that may be difficult to reproduce, or that must be reproduced exactly and without variation across multiple screen prints. Examples where spot color might be used include logos for sports teams printed on officially-licensed merchandise or other trademarks where specific color quality is essential to guarantee visual recognition. To produce a full-color image, the spot color separation method will require more individual screens than the other methods described. Screen printers may use spot color as its own separation method or as a way to supplement process or simulated process color separations with additional hues.
