BULB OF PERCUSSION: in flintmaking, a swelling or bulb left on the surface of a blade or flake directly below the point of impact on the striking platform – that is, a swelling on a flake or blade at the point where it has been struck to detach it from a core. On the flake or blade struck off there is a rounded, slightly convex shape around this point called the bulb of percussion and on the core there is a corresponding concave bulb. The point and the bulb of percussion are rarely present if a flake has been struck off naturally, as by heat or frost. Thus the presence of a bulb of percussion makes it possible to distinguish human workmanship from natural breakage. [bulb, bulb of force]
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