A Guide to Printing & Color MatchingMay 24 '19
Graphic overlays, membrane switches, labels, and nameplates can be printed using either screen or digital printing technologies.
Digital printing is applicable to small lot quantities because it eliminates setup times for colors; it does a better job of printing and can result in shorter lead times.
Screen printing is more economical for larger quantities, or when there is a need to match a PMS color outside the color gamut of digital printing.
Steps in setting and precisely controlling color.
1. Define a reference color. The Pantone Matching System (PMS) is the most commonly used system for specifying a color standard. Learn more. The Pantone “swatch book” contains more than 1000 colors. A less common color system is the Federal Standard 595 – or a sample of the color can be provided.
Pantone & Fed Std 595a limitations: These color systems have two limitations.
1) If the swatch book is not new, colors may have faded and may not be comparable to a new book,
2) The Pantone system was developed for 1st surface printing of lithographic inks on white coated paper. Because inks used are screen printed on the second surface of a transparent material or the material printed on is not a totally opaque white, the color may shift by the transparent material on which the ink is printed.
2. Create a color reference. We create a color reference using the printing process and substrate material to be used in production. The preciseness of the match to a PMS color will be influenced by:
1) the substrate on which the color is printed,
2) the material through which the ink is viewed,
3) if digitally printed, the full-color process printing employed to approximate a PMS color match.
3. Comparing parts vs. the color reference. There are two ways to compare color vs. the reference.
- Visual comparison: Under most circumstances, a visual comparison of the color chip and the production part is sufficient to assure color control. It is important to carry out the color check-in a light booth. Light booths create alternative LED and fluorescent wavelengths, full daylight, variable daylight, and incandescent illumination.
- Instrumentation Comparison: In numerical terms, we can determine the color difference by using a spectrophotometer. Spectrophotometers take numerical readings of color in the 3-D CIELAB color space. The spectrophotometer reads lightness, and chromaticity, reflecting those parameters as numerical values of L*, a*, b*. By comparing the 3D coordinates of a color chip to a production part, we can determine the color difference. Learn more.