What is the Hardness of Paint Film and How to Measure It?

Hardness refers to the resistance of a paint film to the intrusion of foreign objects into its surface. The hardness of the paint film is one of the important properties of its mechanical strength. Generally speaking, the hardness of the paint film is related to the materials and drying degree of the paint film. For example, the more effective the paint film dries, the higher the hardness will be. At present, the determination of the hardness of the paint film has the following four methods: the rod hardness measurement method, the Swaite hardness measurement method, the Kleeman hardness measurement method and the pencil hardness measurement method. Hardness measurement generally needs to be operated on a Hardness Tester, and the pencil hardness measurement method can also be performed manually. The method is as follows:

(1) This method uses a set of pencils to measure the hardness of the paint film. The pencils are generally high-grade drawing pencils produced by the same manufacturer, and the types of pencil leads are HB, H, 2H, 3H, etc.

(2) Hold the pencil with your hand, keep an angle of about 45° with the surface to be coated, use as much force as possible (but not break the pen core), and push the pencil forward at a speed of about 3 mm/s. A pen core with a length of about 3 mm, after reciprocating five times on different parts, wipe off the pencil dust with an eraser or soft cloth, and check the scratches on the paint film. If the paint film remains intact, it is the hardness of the pencil. The pencil hardness test method is mostly used for the hardness test of electrophoretic paints and architectural coatings.