Barcol hardness test the Barcol impressor was developed by Walter Colman as a hand-held, portable means of assessing the hardness of a material during World War II. The United States Army Air Corps required a hand-held method of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing normal rivets with soft lead or wooden ones which would fail during flight. The impressor operates when the tip is pressed against the material in question. The hardness of the material determines how far the tip indents and this is transferred by a tension spring and lever to be read
Bamboo floor range from 3000 to over 5000 using the Janka hardness test. Other flooring materials have comparable Janka ratings, with a higher number indicating a harder material: red oak (1290); white oak (1360); rock maple (1450); hickory (1820); and Brazilian Cherry / Jatoba (2350). Different forms of bamboo flooring exist. Each varies in its manufacturing process and differs largely based on economic viability and local preferences. The most common form, particularly in southeast Asia, uses thin bamboo stems that are cut as flat as possible. They are cut to similar lengths and can be stained, varnished, or simply used as is.