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
Obviously, there is a link between durometer and modulus (Figure 2). The relativity of the two is constant, but the specific modulus for a given durometer can change from one formulation to another. Such differences are typically minor, but they can be just enough for a printer to observe that one brand feels snappier than another. However, as with all properties, there is a trade-off: You cannot change the relative modulus without affecting another property. For instance, you may be able to increase the modulus-to-durometer, but that can have a negative impact on abrasion resistance.
If durometer is the only thing we can practically measure, and it is linked to modulus, is it linked to other criteria in a way that can be useful? Yes, in that there are some tendencies you can count on (Figure 3). For a given squeegee formula, from a single manufacturer, there is an increase in both chemical and abrasion resistance as the durometer increases. Additionally, as durometer increases (same brand and formula), the relative degree of improvement increases in a non-linear fashion. The relative increase in performance from 80A to 85A is greater than the increase in performance from 70A to 75A. That’s why creating an apples-to-apples comparison of durometer is critical when examining two different types of squeegees.
All manufacturers maintain a certain durometer tolerance. The typical range is ±5. A durometer gauge is essential for proper measurement. If you do not have one, talk to your supplier. Do not make assumptions about the fact that you specified 80A for your current squeegee and merely request a sample of the same durometer. For example, if the current product is an 80A that actually reads 84A (within tolerance), and the test sample is an 80A that reads 78A (even closer to spec), you will not obtain a fair comparison.The difference in durometer alone could cause you to perceive that the performance of the sample is not as good. For the test to be fair, the submitted material should be an 85A.
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