The Janka Hardness Scale
The Janka Scale rates the relative hardness of wood. The scale was developed in 1906 by Gabriel Janka, an Austrian wood researcher, and standardized in 1927 by the American Society for Testing and Materials (ASTM). The Janka Hardness Test measures the force required, in pounds per square inch (PSI), to embed a 11.2mm steel ball to half its diameter into the wood. This is one of the best measures of the ability of wood species to withstand denting and wear. It is also a good indicator of how hard a species is to work with, for example to saw or nail. This should only be used as a general guide when comparing various species of wood flooring. Depending on where and how the wood is harvested, processed, treated, dried and stored, the results may vary. Plank construction and finish are also important factors when determining the durability and ease of maintenance of any wood floor. This rating is very important when it comes to matching timber to its intended usage. For example, if you are building a floor where high levels of foot traffic are expected, a more durable timber would be best, and therefore one with a higher Janka rating. If you are a handyman, another point you need to keep in mind about the hardness of wood is that the harder the wood, the more difficult it will be to work with. Unless you have top-of-the-line equipment and a lot of wood flooring experience, you may not want to select the species with the highest Janka rating. Balsa Wood is softest at 22 psi, with the hardest timber measured Australian Buloke at 5060 psi. Many species of Gum measure between 1500 and 2000 psi, whereas Pine radiata measure 710 psi.