THE FIRST STATIC HARDNESS TESTING METHOD WAS INTRODUCED BY J. A. Brinell, a Swedish researcher, at the 1900 Paris World Exposition. A hardened steel ball or tungsten carbide ball with a diameter (D) of 1, 2, 2.5, 5, or 10 mm was used as indenter. This was pressed into the smooth, clean specimen surface with a test force (F). Figure 21.1 shows the principle of test with test force F (N), D the diameter of the ball (mm), d the mean diameter of the indentation (mm), and h the depth of the indentation (mm). It is important that the specimen rests on a rigid support, and that the indenter contacts the specimen without being shaken or jolted. The test force is then increased to the predetermined maximum value within 2-10 s and held for 10-15 s. If the duration of load application falls outside of this range, this must be indicated. For example, for nonferrous materials, the duration may be as long as 180 s.