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A HANDY GUIDE TO DESIGNING FOR FLEXOGRAPHY

CHAPTER 4 - FOUR COLOR PROCESS ART

                    understanding dot gain • highlight areas • supplying a color target • latran prediction proofer

Dot Gain

When designing a job for flexography it is important to understand the term "dot gain" and how it can effect the highlight areas of an image. In the flexo 101 class we learned that four color process art separates into various percentages of cyan , magenta, yellow and black, appearing as cicular shaped dots under a high powered magnifying glass. Dot gain is the physical and/or optical measurement and theoretical calculation of the apparent increase in these dots from one medium to another. In the Flexographic printing industry specifically, it’s the difference in dot area between the digital file and the printed piece. The computed value, which is measured on a densitometer, combines both the physical and optical gain of the dot. Certain variables on press including substrate, impression, ink, anilox, sticky back and overprint varnishes and laminates effect the amount of dot gain that occurs.

Highlight Areas

Where dot gain can become a problem in flexo is when we are dealing with highlight areas. The highlight area on a four color process job is from 1% to about 25%. Under normal circumstances, 1% is the lowest percentage we can hold on our digital plates. Following the growth of this area through the process is crucial if the correct alignment between proof and finished printed product is to occur. Since going to a digital system, one of the most significant improvements we have seen has been in highlight areas. When we had the conventional platemaking system (Film to solvent plates), the lowest dot we could hold on our films was a 2%. This 2% gained considerably thorughout our solvent platemaking process to the point where we would commonly see 18%’s as our lowest printed percentage. Now that we have digital platemaking equipment, we consistently hold 1% dots on our plates. When you factor in that this process is now solvent free, with absolutely zero swelling occurring, our lowest printed percentage is now about 7% . By opening up these highlight areas we have significantly widened our color gamut.