A device used to measure the hardness (also itself called the durometer) of the surface of a printing ink roller, flexographic plate cylinders and rollers, and other rollers used in a variety of printing process. Durometer or hardness is a property that has significant effects on print quality and ink transfer. (See Durometer.) A type-A durometer measures the resistance of a surface to the pressure generated by a spring-loaded probe, the result being indicated on a dial (using units called "durometer units") graduated from 0 (extremely flexible) to 100 (extremely inflexible). The durometers used in roller measurement typically have a 1-kilogram (kg) mass mounted above the probe, which tends to provide more reproducible results. When durometer readings are measured in the pressroom, it should always be performed when the roller is still on the press. If that is not possible, it should be removed and placed in a notched rack. An ink roller should never be placed on a flat surface, lest it develop problems such as out-of-roundness.
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