Retouch (lithics)
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Retouch is the work done to an edge of a stone implement in order to make it into a functional tool, or to reshape a used tool. In the case of a core-tool, such as a hand-axe, retouch may simply consist of roughly trimming the edge by striking with a hammerstone, but on smaller, finer flake or blade tools it is sometimes carried out by pressure flaking. Retouch, also known as secondary working, is one of the most obvious features distinguishing a tool from a waste by-product of lithic manufacture (debitage). On the other hand, retouch can be strategy to reuse an existing lithic artefacts and enable people to transform one tool into another tool. [1]
The extent of reduction, also known as the retouch intensity, is denoted by a measure of the reduction index.[2] There are many quantitative and qualitative methods used to measure this.
Measuring Retouch
Quanitative Measurements
There are three indices of retouch that offer significant inferential power in determining the amount of mass lost in the process of retouching. Despite particular weaknesses associated with each method, the following methods have been shown to be the most robust, versatile, sensitive, and comprehensive.[2]
Geometric Index of Unifacial Reduction (GIUR)
This method uses measurements of flake thickness and the height of retouch scars to produce a ratio between 0 and 1 of the index of reduction. Calipers can be used to measure the height of the retouch scar or a goniometer can be used to measure the angle of the retouch. It is restricted to use on unifacially retouched flakes.[3]
Invasiveness Index
This index divides both the dorsal and ventral surface of a flake into eight sections each and calculates a score of how invasive the retouch is. It is based off of adding up individual scores from each of the eight sections (each section gets a score of 0, 0.5, or 1) and dividing the total by the number of sections. This index can be used on both unifacially and bifacially retouched flakes.[4]
Initial-/terminal-mass comparison (ITMC)
This index estimates the initial flake mass through the use of laser scanners and the measurement of platform area and exterior platform angle. The platform must be fully intact in order to use this method.[2]
Other measures of retouch include:
- Ratio of ventral area to platform area[2]
- Hafted biface retouch index[2]
- Estimated reduction percentage (ERP)[2]
- Ratio of retouched edge to total perimeter
Ethnographic Research
Through ethnographic research in Central Australia, Hiscock found that retouch may be conducted on a flake that is ultimately rejected as a tool for use. This shows that retouch may, in some cases, not be a sign of extending the use life of a tool. It may simply be an attempt to make a tool viable for use in the first place and can indicate that particular tool’s unsuitability for use. [5]
References
- ^ Pelcin,A., 1998, "The threshold effect of platform width: a reply to Davis and Shea", Journal of Archaeological Science, 25, p. 615-620.
- ^ a b c d e f Hiscock, P., & Tabrett, A. 2010. Generalization, inference and the quantification of lithic reduction. World Archaeology, 42(4), 545–561.
- ^ Kuhn, S. 1990 A geometric index of reduction for unifacial stone tools. Journal of Archaeological Science 17:585-593.
- ^ Clarkson, C. 2002 An index of invasiveness for the measurement of unifacial and bifacial retouch: a theoretical, experimental and archaeological verification. Journal of Archaeological Science 29(1):65-75.
- ^ Hiscock, P. "Slippery and Billy: intention, selection and equifinality in lithic artefacts", Cambridge Archaeological Journal, 14(01). p. 71-77.
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