Janka hardness test Janka hardness test The Janka hardness test (from the Austrian-born emigrant Gabriel Janka, 1864-1932) measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an diameter steel ball halfway into a sample of wood. A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the grain, is said to be of "side hardness". Testing the cut surface of a stump is
Scratch hardness Wooddell, working at the Carborundum Company, extended the scale further by using resistance to abrasion, and extrapolating the scale based on seven for quartz and nine for corundum, resulting in a value of 42.4 for South American brown diamond bort. Resistance to abrasion is less affected by surface variations than other methods of indentations. There is a linear relationship between cohesive energy density (lattice energy per volume) and Wooddell wear resistance, occurring between corundum (H=9) and diamond (H=42.5). Scratch hardness Scratch hardness tests are used to determine the hardness of a material to scratches and abrasion. The earliest test was