About Hammer Face "Shore Hardness"
The hardness testing of plastics is most commonly measured by the Shore (Durometer) test. This method measures the resistance of plastics toward indentation and provides an empirical hardness value that doesn't correlate well to other properties or fundamental characteristics. Shore Hardness, using either the Shore A or Shore D scale, is the preferred method for rubbers/elastomers and is also commonly used for 'softer' plastics such as polyolefins, fluoropolymers, and vinyls. The Shore A scale is used for 'softer' rubbers while the Shore D scale is used for 'harder' ones. Other Shore scales, such as Shore O and Shore H hardness, are rarely encountered by most plastics engineers.

The Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as the 'Durometer hardness'. This hardness value is determined by the penetration of the Durometer indenter foot into the sample. Because of the nature of rubbers and plastics, the indentation reading will change over time affected by material ageing and other direct environmental conditions.