You may see the letters CMYK mentioned with regard to the printing process. They refer to printing ink, and 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, the three colors of cyan, magenta and yellow are used in varying amounts to create a gamut that more or less represents all the colors of the rainbow. This is done by the inks subtracting reflected light off the substrate which in our case is white paper.
In theory if you were to combine equal amounts of those three colors what should appear is black, and smaller percentages of equal amounts would create shades of gray. In practice, the impurities of mass-manufactured printing inks will reproduce a dark color, but one that is rarely close to what we would all agree is 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 which is a technical challenge if using the three color inks as minor changes in alignment will make a blurred effect that can be hard to read.
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!