The hardness is measured in a manner similar to the Shore hardness. The penetration depth is measured, which is converted to a Shore hardness number according to a specified chart. This chart should be consulted for the maximum depth of penetration. For easy to use charts, refer to ASTM D-2240, JIS K 6301 and ISO 7619. Prior to the application of a sample, the hardness tester needs to be calibrated with the hardness number and test method, so that the latter is traceable to ca. +/-.06 for ordinary material tests.
Very soft plastics and rubbers have a Shore A value of 1.5 and more and therefore are easily damaged by indentation. The Shore A durometer indicates the properties of natural rubber, synthetic rubbers, silicone rubbers, and many other materials. The durometer is also useful as penetration into the materials increases and is even useful in indenting paper. A slightly firmer durometer of 2 to 3.5 is indicated for many plastics and the durometer is applicable to the Carpet measurement for testing carpeting of 2 to 3 mm. The hardness is usually tested by using the wedge-edge shaped indenter, which is pressed into the sample, and a position is determined that produces a reading of 6 to 15.
The Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as 'Durometer hardness'. The hardness value is determined by the penetration of the Durometer indenter foot into the sample. Because of the resilience of rubbers and plastics, the indentation reading my change over time - so the indentation time is sometimes reported along with the hardness number. The ASTM test method designation is ASTM D2240 00 and is generally used in North America. Related methods include ISO 7619 and ISO 868; DIN 53505; and JIS K 6301, which was discontinued and superceeded by JIS K 6253. d2c66b5586