Scratch tests are performed to assess resistance to the scratching, gouging, scraping or engraving of hard, flat test samples. Scratch tests can also be used to establish the relative purity of samples, quality of protective coatings and effects of ageing on a sample.
To perform a scientific scratch test, a diamond tip is dragged across a surface with either a constant or increasing load. A video camera can be used to record and assess various modes of damage, which can then be correlated to the amount of force used. Specialized equipment can perform scratch tests on a micro- or nano-scale.