There are two main methods: scratching method and pressing method.
(1) The scratch method mainly measures inorganic minerals, also called Mohs hardness. It only indicates the order of hardness from small to large, but does not indicate the degree of softness and hardness.
(2) There are many types of indentation hardness testing methods, commonly used are Brinell hardness, Vickers hardness, Rockwell hardness and Knoop hardness. The principle of these methods is to press a hard object into the surface of the object to be measured under static pressure. The hardness of the object being measured is expressed as the load per unit area when the surface presses into the concave surface.