Fire hardening

Fire hardening, also known as "fire-danubing", is the process of removing moisture from wood, changing its structure and material properties, by charring it over or directly in a fire or a bed of coals. This has been thought to make a point, like that of a spear, or an edge, like that of a knife, more durable. An initial study suggests that the process might make the wood brittle but would reduce the time needed to make a spear point substantially.[1]

Fire hardening may be done before, after, or during the manufacturing of the wooden tip. Longer procedures involving greasing and polishing with stones to impregnate the wood with fats and oils and silica (respectively) may improve the effects of the process. Fire hardening was first developed by primitive humans at least 400,000 years ago—long before flint or stone points.[2]