Janka hardness test
The Janka hardness test measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an 11.28 mm (0.444 in) steel ball into wood to half the ball's diameter. This method leaves an indentation. A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring.
It should be noted that the test is meant to be used only for "unfinished, open grain flooring" manufactured before the 1990s. With the advent of pre-finished flooring in which hardwood floors are treated with aluminum-oxide based sealers that often double or triple the dent and scratch resistance of the flooring, the Janka Hardness test has been essentially rendered useless in modern-day hardwood flooring, unless the end user is purchasing unfinished or oil coated 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 called a test of "end hardness".
The results are stated in various ways, which can lead to confusion, especially when the name of the actual units employed is often not attached. In the United States, the measurement is in pounds-force (lbf). In Sweden it is in kilograms-force (kgf), and in Australia, either in newtons (N) or kilonewtons (kN). Sometimes the results are treated as units, for example "660 Janka".
The Janka Hardness test results tabulated below were done in accordance with ASTM D 1037-7 testing methods. Lumber stocks tested ranges from 1" to 2" thick. The tabulated Janka Hardness numbers are an average. There is a standard deviation associated with each species, but these values are not given. It is important to note no testing was done on actual flooring. Other factors affect how flooring performs: the type of core for engineered flooring such as pine, HDF, poplar, oak, birch; grain direction and thickness; floor or top wear surface, etc. The chart is not to be considered an absolute; it is meant to help people understand which woods are harder than others.
- Johnny W. Morlan. "Wood Species Janka Hardness Scale/Chart By Common/Trade Name A - J". The World's Top 125 Known Softest/Hardest Woods. Retrieved 20 December 2011.
- "Red Maple". The Wood Database.
- "Silver Maple". The Wood Database.
- Janka Hardness Scale For Wood Flooring Species
- Janka Hardness Scale For Wood - Side Hardness Chart of Some Woods
- The World's Top 125 Known Softest/Hardest Woods
- USDA - Wood Handbook - Wood as an Engineering Material
- USDA - Janka Hardness Using Nonstandard Specimens
- Janka Hardness Scale For Hardwood Flooring