When selecting a Squeegee, the first task is to determine your desired durometer, or hardness. The durometer is the value that reflects the physical hardness of the Squeegee material. The Squeegee durometer values from 50A to 95A. This is measured by a durometer gauge, and measured based on standards established by ASTM procedures. (American Standard Testing materials) . For the sake of simplicity, we will call soft – 60-65A, medium – 70-75A, and 80-85A – a hard Squeegee, and 90-95A -extra hard. Plastics/Squeegees are measured in various scales of hardness. Shore A scale is the most widely used for measuring Squeegee material. Like a tension meter, a durometer gauge should be calibrated on a regular basis. (1 time per year). The small needle head penetrates into the material, and indicates the hardness of the rubber.
Typically the substrate and the screen mesh will directly determine the durometer selected. For example, if the substrate has an irregular or rough surface and requires a coarse mesh, then a squeegee with a durometer between 60 and 75A is recommended. If the substrate is smooth, however, and a high mesh count is being used, a harder durometer squeegee between 80 and 95, should be used. The most popular durometer regardless of industry specific, is the 70-75 durometer blade. Why? The Squeegees job is to shear the ink, and transfer the ink through the screen. So, the blade needs to be rigid enough for this, yet needs to be soft enough to adapt to the contour of the Screen. A 70-75 durometer blade gives the printer the best of both worlds. A softer blade, but not soft enough to the point where it will roll over and loose ink shear. The more aggressive inks such as UV inks cause more harm to the blade than a standard plastisol or water based ink. The harder the material, the more solvent resistant the blade. Therefore, to eliminate swelling and chemical breakdown, use a harder durometer Squeegee.