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'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle

Ennos, Antony Roland; Chan, Tak Lok


Antony Roland Ennos

Tak Lok Chan


It is usually assumed that 'fire hardening' the tips of spears, as practised by hunter-gatherers and early Homo spp., makes them harder and better suited for hunting. This suggestion was tested by subjecting coppiced poles of hazel to a fire-hardening process and comparing their mechanical properties to those of naturally seasoned poles. A Shore D hardness test showed that fire treatment slightly increased the hardness of the wood, but flexural and impact tests showed that it reduced the strength and work of fracture by 30% and 36%, respectively. These results suggest that though potentially slightly sharper and more durable, fire-hardened tips would actually be more likely to break off when used, as may have been the case with the earliest known wooden tool, the Clacton spear. Fire might first have been used to help sharpen the tips of spears, and fire-hardening would have been a mostly negative side effect, not its primary purpose.


Ennos, A. R., & Chan, T. L. (2016). 'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle. Biology Letters, 12(5), Article 20160174.

Journal Article Type Article
Acceptance Date Apr 14, 2016
Online Publication Date May 18, 2016
Publication Date May 18, 2016
Deposit Date Apr 19, 2016
Publicly Available Date Oct 27, 2022
Journal Biology letters
Print ISSN 1744-9561
Electronic ISSN 1744-957X
Publisher The Royal Society
Peer Reviewed Peer Reviewed
Volume 12
Issue 5
Article Number 20160174
Keywords Wood; Spears; Fire hardening; Hardness; Mechanical properties
Public URL
Publisher URL
Additional Information Authors' accepted manuscript of article published in: Biology letters, 2016, v.12, issue 5, article no.20160174


Article.pdf (110 Kb)

Copyright Statement
© 2016 The Author(s)
Published by the Royal Society. All rights reserved.

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