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White ink is used extensively in printing plastic films for packaging. The role of the white print is to totally or partially block the package ingredients and provide an opaque print contrast for line and process colors. Colors on the press are controlled to an appearance standard with a spectrophotometer. This level of instrumental control also fixes the application rate, and as a direct result, the cost of ink use becomes predictable for the colors.
Management of white ink application can be a different story. With white ink, the usual measure of graphic performance is opacity. Other factors, such as gloss or whiteness, also can be important, but opacity is the primary determiner in cost analysis. Technically, opacity is the ability to block light coming through the package. However, it also governs how the color graphics stand out in contrast and the overall vividness of the image.
Often, white ink printed on film is not well controlled even when more than half the ink coverage...