Evaluating squeegee materials for quality and performance on press is one of the keys to successful screen printing. This article describes material formulations, essential vocabulary, and criteria for making effective comparisons.
By James Elliot
Chemical resistance and durometer If one squeegee just turns to jelly when exposed to an ink or chemical, the point is obvious. However, this is seldom the case. A good means of examining chemical resistance is to measure the durometer of fresh material for each brand right before printing. Put each on press under similar circumstances and set a fixed interval of time or impression count, pull each squeegee off of the press, and measure the durometer. For example, if your run length permits, run both squeegees for one shift and measure the durometer of each in two-hour intervals. Write down the number of impressions each has printed in case there’s a big difference. At the end of the day, measure, clean, and let the squeegees sit until the next day. Measure again to look at recovery. Different brands frequently show different rates of durometer loss for different inks, as well as different rates of recovery. This is extremely important for work such as four-color-process printing. The rate of durometer loss (Figure 4A) plays a role in the degree of dot gain during a run. You can cut samples, submerge them in ink and measure them at intervals, but you’ll often see that the dynamic results under printing are different from those obtained from static testing. Durometer measurements should be taken from at least three areas across the blade that are constantly exposed to ink, then the measurements should be averaged.
Swell Noticeable swelling has little impact on the performance of some squeegee materials, while for other formulations it means a trash can is in the near future (Figure 4B). Again, measure durometer when you see swelling, then visually examine the material and measure durometer after relaxing the squeegee at least overnight.
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