Shore Hardness

Shore Hardness or Durometer is one of several measures of the hardness of a material.

Hardness may be defined as a material’s resistance to permanent indentation. The durometer scale was defined by Albert Ferdinand Shore who developed a device to measure Shore hardness in the 1920s. The term durometer is often used to refer to the measurement as well as the instrument itself. Durometer is typically used as a measure of hardness in polymers, elastomers and rubbers.

Shore’s device was not the first hardness tester nor the first to be called a durometer  today that name usually refers to Shore hardness (other devices are simply called hardness testers).

Durometer, like many other hardness tests, measures the depth of an indentation in the material created by a given force on a standardized presser foot. This depth is dependent on the hardness of the material, its viscoelastic properties, the shape of the presser foot, and the duration of the test. ASTM D2240 durometers allows for a measurement of the initial hardness, or the indentation hardness after a given period of time. The basic test requires applying the force in a consistent manner, without shock, and measuring the hardness (depth of the indentation). If a timed hardness is desired, force is applied for the required time and then read. The material under test should be a minimum of 6.4 mm (0.25 inches) thick.