Name one common test used for measuring the hardness of paint films.

The pencil hardness test is a widely recognized method for measuring the hardness of paint films. This test involves using pencils of varying hardness, typically graded on the Mohs scale, ranging from very soft (e.g., 2B) to very hard (e.g., 6H). By applying these pencils to the painted surface under controlled pressure, the test assesses the resistance of the paint to scratching. A higher hardness rating indicates that the paint film has better resistance to wear and degradation, which is essential for durability in various applications.

While the other tests mentioned serve important functions in evaluating different properties of paint films, they do not specifically measure hardness. The impact resistance test evaluates how well a paint film can withstand sudden force or impact, while the adhesion test measures the ability of the paint to bond to a substrate. The flexural strength test assesses how a material behaves when subjected to bending. None of these tests focus solely on the hardness characteristics of paint, which makes the pencil hardness test the most relevant answer for measuring this specific property.