Fire hardening, also known as "fire-danubing", is the process of removing moisture from wood, changing its structure and material properties, by slowly and lightly charring it over a fire. 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.
Pre-historic weaponmakers would rub the end of a selected wood pole against a smooth rock surface until a point was achieved. Then the point was heated in a fire, making sure to thrust the point into the coals. This put a light coating of carbon on the surface, which was then polished with a special stone, which ground fine particles of stone into the pitch which had been brought to the surface of the wood by the fire. Subsequent firings and polishings of the wooden tip of the spear would eventually form a hardened glaze consisting of pitch, wood particles and carbon on the tip which could eventually be even harder than a copper tip. This kind of technology was developed by primitive humans at least 400,000 years ago—long before flint or stone points.
- Ennos, A. R., & Chan, T. L. (2016). [url=https://www.webcitation.org/6t0iBAGeP?url=http://rsbl.royalsocietypublishing.org/content/12/5/20160174 ‘Fire hardening’ spear wood does slightly harden it, but makes it much weaker and more brittle.] Biology Letters, doi:10.1098/rsbl.2016.0174
- H.L. Fluck. Initial Observations From Experiments Into The Possible Use Of Fire With Stone Tools In The Manufacture Of The Clacton Point. 2007. Lithics: The Journal of the Lithic Studies Society 28: 15–19.
- H.L. Fluck. (2016) Initial Observations From Experiments Into The Possible Use Of Fire With Stone Tools In The Manufacture Of The Clacton Point. Lithics: The Journal of the Lithic Studies Society 28: 15–19.