Spot color

A spot color, also known as spot color or spot color printing is a printing ink used in addition to the primary colors in multi- color printing. The term covers solid colors for additional color depth extent, as well as special effect colors.

• A solid color can not be composed of the standard colors. This is neither in the four-color printing, which is based on the CMYK color model (cyan, magenta, yellow and black ) ( usually the process colors or background colors of the Euro scale) possible, even in the six- color printing. The reason is that the gamut of color printing some important areas of color not taken into account: colors mix remain As with any three- (or four- printing ) color- rich, highly colorful tones can not be represented ( solid colors ). Especially in the area of ​​green and deep blue the CMY color mixing shows significant weaknesses. By adding further color gamut is expanded.
• Also an opaque white that is in its whiteness outside the limited on paper white gamut, one of the special colors, or the opaque Rubbellosfarben PIN assignments.
• Continue playback through screening ( in image processing: dithering) of light and dark colors with the deep color to blackening in pastel colors to color vision deficiency, so that even in these areas, such as art print, spot colors are required.
• Effect colors such as gold or silver colors or fluorescent colors, have also made ​​beyond characteristics in terms of gloss and other effects.
• For surfaces in Volltonabbildung, is required in the area-wide application of paint, be necessary in mixed media with screen printing special colors: metallic effect colors are very highly opaque and partially overprinted and can lose much of their luster effect during rasterization, since there is no closed surface more. If you do it anyway, totally unpredictable color effects can occur with incorrect color sequence when pre-printed spot colors are partially covered with the gridded, opaque metal color. The thereby resulting iridescence is characterized by moiré effects and / or strong color variations from one sheet to the next.

By the use of spot colors, it is also possible to print colors which are outside of the four possible color gamut. The spot color, as printing inks, the special optical, has " decorative " properties will be printed as a separate, " separate " pressure transition. In today's conventional four - color machines that print all four process colors in a single pass, the spot color requires a separate printing operation, which can lead to sometimes significant additional costs as a 4-color machine is then assigned for this 5 - color job twice as long, or two separate printing units in the merge are required. In modern photographic printing is used in addition to the four CMYK colors - here referred to as " spot color " not quite in the sense of the term - even light cyan and light magenta ( six- color printing ), two shades of gray, or even six basic colors of a combined RGB - CMY system with black and gray as primary colors, but also, if necessary, additional spot colors.

Common spot color palettes for the pressure final stage are HKS ( highly saturated colors like HKS 61 or 84, or opaque HKS 88K ) and Pantone subjects ( eg 801 - 814C, 871- 877C for effect colors), and the RAL color system defined as pearlescent special colors. Are intended spot colors are not available, they can be approximated from the printed process colors.

The Kiss, Gustav Klimt, 1907-1908 ( Golden period ), oil on canvas with gold leaf application - for reproduction of this image is a gold special-effect color required ( 2)