Many times, a customer requests a specific color other than black, cyan, yellow, or magenta on the ink required, the printer either orders the specific color from the inkmaker or mixes it in the printing plant. Obtaining the ink from the inkmaker is preferred if the color is a shelf ink or if the amount required is large. Small amounts of a particular ink can be mixed in the plant. Color charts from an inkmaker are extremely helpful.
In plants where a great deal of color matching is done, the press operator seldom mixes the ink. A better way-both economically and from a quality control standpoint - is to have a special person assigned to do color matching.
The simple rule of good color matching is to use the formula method. Every mixed color that is used in the plant should have each ingredient carefully weighed and recorded. This includes additives like driers. See Figure 5-14.
When the proper shade is found, a large batch is mixed, following the formula. After the color is printed on the job, a small sample from the printed sheet is saved, and the formula and date are marked on the back. A sample should not be kept too long, perhaps one year for lightfast colors. In addition, the name and/or number of the job should be put on the sample in case of a reprint. The inks are then listed, with brand, name, number, and weight indicated.
Ink samples can be drawn out with a spatula, rolled out with a Quickpeek tester, or printed using a proof press and allowed to dry. Exposing one sample to atmospheric conditions overnight and enclosing the other in a book gives an indication of the drying behavior of the ink.
sometimes, two or three small color samples are mixed if the color is expected to change during drying. For example, if a green made a certain blue and yellow is expected to dry toward the blue side, a second sample would be made with less blue in it. The one drying closest to the desired color is used. If the desired color falls between two samples, a new sample can be mixed, using the formulas from the first two samples as the basis for the new formula.
A tint of a color is produced by adding an extender, a white transparent tinting medium, to a colored ink. The simplest form of color matching, as performed by the printer, is mixing an ink to obtain a required shade. The stronger color should always be added to the lighter colored ink in order to obtain a match more quickly and economically. The color should be viewed under different light sources to check for metamerism -- the phenomenon of colors that match under one light but do but under a different light.
Without a knowledge of color theory and without perfect color perception, an individual will resort to trial-and-error matching. Fortunately, color matching systems are available that take the trial and error out of color matching.