You may see the letters CMYK mentioned with regard to printing. While it may seem to be an acronym for Cyan, Magenta, Yellow and Black, on closer inspection you’ll note it does not.
The obvious issue is the letter K which oddly enough stands for the “key” as in the key plate. Just as with a keystone, the key plate is a crucial part of color reproduction.
In the subtractive color model, cyan, magenta and yellow inks are used in varying amounts to create a variety of shades and hues that more or less represent all the colors of the rainbow. This is done by the inks subtracting reflected light off of our white paper.
In theory, if you combine equal amounts of those three colors what should appear is black. Smaller percentages of equal amounts would thus create shades of gray. In practice, however, the impurities of mass-manufactured printing inks will produce a dark color, but one that is rarely close to what we would call “black.”
This is where the Key plate comes into play. In printing, the key plate is used with black ink. Since this ink is a purer black than the three process inks can produce added together, images reproduced on press will have richer contrast and darker areas will look neutral.
Black ink can be manufactured less expensively than cyan, magenta, and yellow, so when color separations are made, the three colors are often replaced with certain amounts of black which is an added benefit.
Black ink is also used for type. This has the advantage of producing sharp type with only one impression on press. If we instead used the three color inks, minor changes in alignment would create a blurred effect that made the type unreadable.
So next time you see the letters CMYK, you’ll be a little wiser as to how key the letter K can be in making a good impression in your printed bulletin or newsletter!