Kynäkovaustesti

Kynäkovaustesti, sometimes translated as pencil hardness test, is a simple scratch test used to determine the relative hardness of a surface coating. The test is commonly employed in the paint, varnish, and plastic industries. It involves using a set of calibrated graphite pencils of varying hardness, typically ranging from 9H (hardest) to 7B (softest), as defined by the grading system for art pencils.

During the test, a pencil is held at a 45-degree angle to the surface being tested and is pushed across the surface with a consistent force. The pencil is then dragged along the surface for a specified distance, usually 1 cm. The hardness of the coating is determined by the softest pencil that can scratch or mar the surface. If a pencil of a certain hardness leaves a visible scratch, then the coating is considered softer than that pencil. Conversely, if a pencil of a certain hardness does not cause any damage, the coating is considered at least as hard as that pencil.

The pencil hardness test provides a quick and inexpensive method for quality control and comparison of different coatings. It is particularly useful for assessing the scratch resistance of automotive finishes, furniture coatings, and protective films. The results are qualitative and depend on factors such as the applied force, the angle of the pencil, and the operator's technique. Therefore, it is crucial to perform the test consistently and under controlled conditions to ensure reproducible results. The scale of pencil hardness is not absolute but rather a relative measure for comparative purposes.