Most materials can withstand the initial pressure, but will yield over time due to creep and relaxation. The reading of the hardness tester can be read immediately or after a specific delay time, usually 5 to 10 seconds. An instant reading will always show a higher (or harder) reading than a delayed reading. The delayed reading is more representative not only of the hardness of the material but also of its elasticity. A weaker, less elastic material is more prone to creep than those that are stronger and more elastic.
In order to ensure the validity of the data, it is necessary to have precise testing procedures. In order to obtain accurate readings, you must have a specimen with a flat surface and a thickness that prevents the indenter from being affected by the supporting surface. The required thickness is usually 0.200 inches, but for hard materials with less deformation, it can be tested accurately when the thickness is thinner.
