Durometers, or hardness testers, are used to determine the hardness of a material to deformation. Hardness measurements quantify the resistance of a material to plastic deformation.

The Durometer is typically used to measure the hardness in polymers, elastomers and rubbers. There are several scales of durometers, used for materials with different properties. The two most common scales, using slightly different measurement systems are the ASTM D2240 type A and type D scales. The A scale is for softer plastics and rubber, while the D scale is for harder ones. However, the ASTM D2240-00 testing standard calls for a total of 12 scales, depending on the intended use; types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. Each scale results in a value between 0 and 100, with higher values indicating a harder material.

The Leeb Rebound Hardness Tester is one of the four most used method for testing metal hardness. This portable method is mainly used for testing sufficiently large metal workpieces (mainly above 1 kg). Leeb metal hardness testers are portable and can be used at different angles as long as they are perpendicular to the test surface. Since the Leeb Hardness Tesater is electronic in nature, it is designed to automatically convert from the Leeb number to a more conventional hardness scale.

The Barcol Impressor, or Hardness Tester, as a hardness test characterizes the indentation hardness of materials through the depth of penetration of an indentor, loaded on a material sample and compared to the penetration in a reference material. The method is most often used for composite materials such as reinforced thermosetting resins or to determine how much a resin or plastic has cured. It is inexpensive and quick, and provides information on the cure throughout a part.