Janka hardness

A standard measure of how much force is needed to press a small steel ball halfway into a sample of wood, quoted in pounds-force or newtons.

Luthiers use it as a rough guide to how well a wood will resist wear, which matters most for fingerboards, where strings and fingernails are dragged across the surface for years. A higher Janka figure usually means slower wear and a brighter, harder contribution to tone, though the measure says nothing about stiffness or movement with moisture, which matter just as much. It is also used to judge whether a species is workable and how well it will hold a screw.

Example: an ebony fingerboard, with one of the higher figures among guitar woods, will stay smooth where a soft species would quickly groove.

Janka hardness

See also