Predicting Spot Color Overprints

To make it even more complex, each printing process overprints differently. Flexo does not overprint like gravure—the ink film thickness and trapping properties are very different. Then, consider the unique information needed to accurately predict the overprint behavior of two custom spot colors: on a given flexo press, with a given anilox, at a given linescreen, with food grade inks. Using typical L*A*B* based measurement, the industry has become adept at making solid colors appear similar across different printing processes, but this leaves room for improvement. For a combination of four inks you need a CMYK IT8.7/4 test chart that actually prints 1617 patches—costly and time-consuming. The number of patches required to print grows exponentially with each additional ink.