Bulb of applied force
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In lithic analysis, a subdivision of archaeology, a bulb of applied force (also known as a bulb of percussion or simply bulb of force) is a defining characteristic of a lithic flake. When a flake is detached from its parent core, a portion of the Hertzian cone of force caused by the detachment blow is detached with it, leaving a distinctive bulb on the flake and a corresponding flake scar on the core. Bulbs of applied force may be distinctive, moderate, or diffuse, depending upon the force of the blow used to detach the flake, and upon the type of material used as a fabricator. Generally, the harder the material used as a fabricator, the more distinctive the bulb of applied force.
When explained visually, the bulb of percussion is visible on the ventral face as oppose to the dorsal face (where it is smoother) and considered to be on the "inside" of the parent core. The bulb of percussion is the primary feature that identifies the ventral surface of a flake or blade artifact. Locating its position reveals which is the proximal end of an artifact. Typically, the striking of the flake is produced by knapping, (or flintknapping) a process in which requires the user to chip away material from high silica stones like "flint" in a carefully controlled manner with special tools to produce sharp projectile points or tools.
- Cotterell, Brian & Johan Kamminga 1987. The formation of flakes, American Antiquity, 52:675-708.
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