The pendulum hardness test is based on the principle that the amplitude of the pendulum’s oscillation will decrease more quickly when supported on a softer surface. There are several hardness tests which relate the damping of an oscillation motion to the hardness of surfaces.

• The Persoz test measures the time for the amplitude to decrease from 12° to 4°.
• The Konig measures time taken from 6° to 3°.

The times taken in Persoz tests are approximately double those in Konig tests and so the Persoz has a greater degree of discrimination.