The pencil hardness test, also referred to as the Wolff-Wilborn test, uses the varying hardness values of graphite pencils to evaluate a coating’s hardness.

The Elcometer 501 Pencil Hardness Tester has been designed to ensure that the cylindrical pencil lead is maintained at a constant angle of 45° and exerts a force of 7.5N (1.68lbF).
The pencil lead, prepared beforehand using the special sharpener and abrasive paper, is inserted into the Elcometer 501 hardness tester and pushed over the smooth, flat coated surface.

The lowest hardness value of the pencil which marks the coating determines the coating’s hardness rating.