Retouch (lithics)
Retouch is the act of producing scars on a stone flake after the ventral surface has been created.
[2] Depending on the form of classification that one uses, it may be argued that retouch can also be conducted on a core-tool, if such a category exists, such as a hand-axe.
Retouch is often taken as one of the most obvious features distinguishing a tool from a waste by-product of lithic manufacture (debitage).
[3] 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.
[4] The new method creates more data points and may erase biases caused by high variation in artefact thickness.
[6] Typically, higher GIUR values indicate more invasive or extensive retouch.
[6] Limitations of the GIUR are its restriction to use on unifacially retouched flakes and that as values increase, they are less able to accurately represent mass loss, because once retouch meets or succeeds the dorsal spine, t/T ratios decline[7] 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.
These are short, become wider at their distal end, and along the flake edge have an acute angle.
These are short, have stepped terminations at their distal end, and along the flake edge have a higher angle.
This is retouch that is struck from the ventral surface, causing scars to show up on the dorsal margin.
This is retouch that is struck from the dorsal surface, causing scars to show up on the ventral margins.
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.
T = overall artefact thickness
t = height of retouch scar
This diagram shows how to calculate the GIUR of a unifacial lithic artefact as described in Hiscock and Clarkson (2005). [ 4 ] Each measurement is taken at three points along the reduced edge (denoted here by subscript) and t/T ratios are calculated and averaged to produce the artefact's GIUR value. This value increases proportionally to the amount of reduction.
