Durometer is a measure of how hard a material is. Technically, it’s a measure of how hard it is to permanently indent a material. There are actually 12 different durometer scales each measured from 0 (softest) to 100 (hardest), but for the we’ll mainly be talking about Shore A since it’s the most common in fluid sealing applications.

How is Durometer Measured?

Measuring durometer is fairly simple. You put a standard metal rod at a standard pressure on to a material for 15 seconds, then you measure the depth of the indentation. For example, in Shore A durometer testing, 1.1 to 1.4 mm diameter steel rod with is applied with .822 Kg of mass (1.81 lb) on a sheet of rubber for 15 seconds.

Which Durometer is right for your Project?

Property	Low Durometer	High Durometer
Durability	Less Durable More easily marked	More Durable Harder to mark
Compressibility	More Compressible	Less Compressible
Flexibility	More Flexible Better for curved surfaces	Less Flexible