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Retouch (also called secondary working or secondary flaking (http://www.archaeologywordsmith.com/lookup.php?category=&where=headword&terms=retouch)) is the act of producing scars on a flake after the ventral surface has been created. It can be done to the edge of an implement in order to make it into a functional tool, or to reshape a used tool. Retouch can be a strategy to reuse an existing lithic artifact 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. There are many quantitative methods used to measure this. Quanitative measures of retouch 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 (Hiscock and Tabrett Generalization, inference and the quantification of lithic reduction). 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 (Kuhn, A Geometric Index of Reduction for Unifacial Stone Tools). 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 (Clarkson, An Index of Invasiveness for the Measurement of Unifacial and Bifacial Retouch…). 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 (Hiscock and Tabrett, Generalization, inference and the quantification of lithic reduction). Other measures of retouch are: Ratio of ventral area to platform area (Hiscock and Tabrett) Hafted biface retouch index (Hiscock and Tabrett) Estimated reduction percentage (ERP) (Hiscock and Tabrett) ratio of retouched edge to total perimeter Qualitative measures of retouch Retouch Morphology This consists of identifying the scar morphology of the retouch. There may be more than one type of scar morphology on a single flake. There are three types of scar morphology. Scaled retouch scars These are short, become wider at their distal end, and along the flake edge have an acute angle. Stepped retouch scars These are short, have stepped terminations at their distal end, and along the flake edge have a higher angle. Parallel retouch scars These are roughly parallel to one another and run along the flake margin. Retouch Direction This is essentially the direction in which the retouch was removed. There are five common directions of retouch. 1. Obverse retouch This is retouch that is struck from the ventral surface, causing scars to show up on the dorsal margin. This happens to be the most commonly present retouch direction. 2. Inverse retouch This is retouch that is struck from the dorsal surface, causing scars to show up on the ventral margins. 3. Alternate retouch This is present when obverse retouch is apparent on one flake margin, while inverse retouch is apparent on the opposing flake margin. 4. Alternating retouch This is when obverse and inverse retouch are both present on the same flake margin, but on differing parts of that margin. 5. Bifacial retouch This is when obverse and inverse retouch are present on the same area of the same flake margin. Retouch Location This is quite simply a description of where exactly the retouch is located on the flake. The key here is to be very specific. The retouch extensiveness for each area should also be described. This entails whether the retouch is total or partial. Proper flake terminology should be used in these descriptions. Forms of retouch: burination - retouch that is conducted in a parallel orientation to the flake margin 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. [2]