In order to prevent the test base (e.g. the test anvil) from affecting the test result in any way, a minimum specimen thickness must be observed with the Brinell method (acc. to ISO 6506).
This minimum specimen thickness must be eight times the indentation depth for the Brinell method and can be taken from the table below.
Minimum specimen thickness (in mm) for the Brinell method as a function of the average indentation diameter (in mm):