This method involves measuring how deeply an indentor penetrates into the material, using an indentor loaded via a spring with specified characteristics. The harder the material to be tested, the higher the indentor loading.  A range of different Shore scales have been established, using different indentor forms and spring characteristics. The best-known scales are Shore A and D, with additional scales such as Shore B, C, 0, 00, 000, and D0 for specific applications. Applications range from soft elastomers (Shore A) to thermoplastics (Shore D).  Both analog Shore hardness testers and digital versions with PC connection options are available from Zwick.

Ball indentation hardness to ISO 2039-1 is used for harder materials. A spherical indentor under constant load is pressed into the material to be tested. The indentation depth under load is used to determine the hardness value.

ISO 2039-2 and ASTM D 785 specify various Rockwell hardness scales for plastics testing. In contrast to ball indentation hardness, where the indentation depth is measured under load, measurement of the indentation depth with the Rockwell method takes place under a defined pre-load. Various indentors are available according to the Rockwell scale in use.