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Hardness can be defined as a material’s resistance to permanent deformation.Scratch Resistance: To assess a coating’s resistance to scratch there are a number of different instruments that can be used: Pencil Hardness Tester (Wolff-Wilborn), Sclerometer, Clemen Apparatus, Scratching and Shearing Instrument. Resistance to Indentation: There are many instruments available to assess the resistance to penetration. For coatings in particular, there are three common methods where the depth of penetration of a weighted tool is used to show the coating’s resistance to penetration: Buchholz, Barcol, Shore. Pendulum Hardness Test: Another way to determine a coating or substrate’s hardness is to use the pendulum method. The pendulum method (Persoz & K?nig) uses the concept of friction. Essentially, a pendulum of a fixed weight rests on the coated surface via two ball bearings. The softer the material, the more the bearings will sink into the surface or coating.