The Brinell Test & Brinell Hardness Numbers

The Brinell test (named after Swedish scientist Johan August Brinell) was originally designed to test the hardness of metals by pressing a 10mm steel ball against the test object and then calculating the area of indentation.

This method has now been adapted for wood floors. A steel ball is pressed against the wood at a load of 100kg. The hardness of the wood is given by the Brinell Hardness Number - or BHN. The higher the number, the harder the floor.

How is the Brinell Hardness Number calculated?

The Brinell Hardness Number is the test force divided by the curved surface area of the indent. the indentation is considered to be spherical with a radius equal to half the diameter of the ball, and the force is maintained for a specific time, normally 10 - 15 seconds. This is called the dwell time.

After the dwell time is complete, the size of the round indent in the sample is determined by measuring two diagonals of the round indent, using either a portable microscope or one that is integrated with the load application device.

To the right is a table showing the Brinell Hardness Number for some of the more common species of wood. Be aware that these values will vary from manufacturer to manufacturer because each manufacturer uses their own source of raw timber. However it should give you an idea of which kind of floors are tough and indent resistant.