In order to use it a weight of known mass is added to the scale arm at one of the graduated markings, the tool is then drawn across the test surface. A scratch tool with a sharp rim is mounted at a predetermined angle to the testing surface. This tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. One tool to make this measurement is the sclerometer.Īnother tool used to make these tests is the pocket hardness tester. The most common test is Mohs scale, which is used in mineralogy. When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The principle is that an object made of a harder material will scratch an object made of a softer material. Scratch hardness is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object. For practical reasons conversion tables are used to convert between one scale and another. Within each of these classes of measurement there are individual measurement scales. There are three main types of hardness measurements: scratch, indentation, and rebound.

Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. In general, different materials differ in their hardness for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics.

In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by pressing or abrasion. For other uses, see Soft (disambiguation) and Hard (disambiguation).

Peek material hardness scale