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Predicting and Managing Dot Gain

(December 2011) posted on Wed Jan 11, 2012

The advice shared here will help you anticipate the dot gain you’ll experience in your garment-printing work and minimize its ne

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By Screen Printing's Solution Sourcebook

Testing allows you to build a profile of gain characteristics for the art department. Begin by creating a series of 20-step grayscale patterns in several halftone line counts. Generate a film positive of this test sheet (Figure 1), then use it to create a stencil following the same screenmaking techniques you plan to use in production. When the screen is complete, use it to produce sample prints of the grayscale pattern. Run test prints with inks in several different colors (white, black, and a few primary colors) and viscosity ranges.
Don’t forget to use proper printing speed. Aim for the best quality possible. You’ll then be able to use the test results as a reliable standard for all your prints. Keep in mind that this test will only give you results as good as your best efforts in screen creation, press setup, squeegee selection, and careful printing. Treat your tests as if you’re running a crucial job for your most demanding customer. Use your best equipment and methods.

To evaluate your test results, compare the original film positive used to produce the test screen or a computer printout of the test pattern with your test print (or with your first and last test prints if you did a volume run of the test). You should be able to see where the gray values match up and where they don’t (Figure 2) when comparing these items under identical lighting. Look at the 10-90% tonal areas, compare them with the same areas on the computer printout, and determine the shift in tonal value you’re seeing. For example, do the 10% dots look more like 20% or 30%?

Look for situations in which there may be more apparent dot gain in the midtones and shadows than in the highlights—a possible indication too much ink flow (the need for a higher mesh count) or poor screen tension. The goal is to have even dot gain in most areas. When you do, the final print in your test run is likely to appear more stabilized than some of the earlier prints you generated.


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