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Test that aims to determine hardness of a coating film by measuring the depth of a V-shaped cavity formed by running a sharp metal wheel carrying a constant weight on dried coating film.
Test method used to determine the surface hardness of a dry organic coating film using a pencil with standart hardness. For pencil hardness test, pencils of following standarts are used arranged in increasing hardness level: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H. Coated surface is scratched with a pencil tip, square shaped with sand paper. A coating’s pencil hardness is defined as the hardness that is one level softer than the softest pencil leaving a permanent mark on the surface.
Hardness measured by marking the coating film using a diamond tip that carries a certain weight. Knoop hardness is calculated by dividing the mass, that applies the weight, by the area of the mark observed on the surface.
A test method at which an instrument records the motion of a sharp indenter impressed into the paint film at slightly increasing loads. Carrying out this test, makes it possible not only the measurement micro-indentation hardness of the coating but also the determination of the elastic and plastic deformation thresholds of the paint film.
An oscillating pendulum, which is in contact with the paint film through two semi spherical touch points, damps according to non-elastic response of the paint film in due course and eventually stops. The time passed for the swing of the pendulum to be damped, is accepted as a measure of paint film hardness.
Measure of resistance of a paint film to scratch, indentation and fatigue deformation.
Vast majority of tests for measuring the hardness of organic coatings are based on the following three principles: scratch resistance, indentation resistance and fatigue resistance against periodic deformation.

Widely used scratch resistance test is the pencil hardness test. Pencils with varying hardnesses are used to scratch the paint film. The hardness of the film is reported as the grade of pencil that does not cause any scratching on the surface.

In indentation resistance tests, an indenter harder than the organic coating is forced against the film under a fixed load. The size of the indentation indicates the resistance of the paint. Buchholz hardness test and Tukon (Knoop) hardness test are the most known indentation hardness tests.

Pendulum hardness test is the most common test relateed to fatigue resistance against periodic deformation. The damping time or number of swings made by the pendulum required to make permanent deformation of paint film under periodic load is determined.

See Also Pencil hardness , Buchholz hardness, Knoop hardness, Pendulum hardness