What is durometer or Shore hardness and how is it measured?

There is an instrument called a durometer which has a spring-loaded indenter that pushes into the surface of a flexible material like polyurethane. It measures the amount that it penetrates, and this is called the durometer hardness of the material. There are two durometer scales, the A-scale and the D-scale that are most commonly used in measuring the hardness of polyurethanes. The "A" scale durometer reads from zero to 100. A measurement of 100 means that the indenter did not penetrate the material at all (i.e., infinitely hard) whereas a measurement of zero implies nearly no resistance of the material. As examples, a rubber band is about 20A, car tires and running shoe soles tend to be about 75A, hard skateboard wheels about 95A. The D-scale is for harder materials; the 95A skateboard wheels would be about 40D. "Shore" is a company name for a durometer instrument, so "Shore" and "durometer" mean the same thing. ... more

There is an instrument called a durometer which has a spring-loaded indenter that pushes into the surface of a flexible material like polyurethane. It measures the amount that it penetrates, and this is called the durometer hardness of the material. There are two durometer scales, the A-scale and the D-scale that are most commonly used in measuring the hardness of polyurethanes. The "A" scale durometer reads from zero to 100. A measurement of 100 means that the indenter did not penetrate the material at all (i.e., infinitely hard) whereas a measurement of zero implies nearly no resistance of the material. As examples, a rubber band is about 20A, car tires and running shoe soles tend to be about 75A, hard skateboard wheels about 95A. The D-scale is for harder materials; the 95A skateboard wheels would be about 40D. "Shore" is a company name for a durometer instrument, so "Shore" and "durometer" mean the same thing. ... more