When a flake is trimmed or reduced by flaking, archaeologists refer to it as ‘retouched’. Retouching was often done to sharpen or repair a tool, or to modify its use.
Retouching was practiced by our earliest stone-flaking ancestors. These tools are found in Oldowan sites at Olduvai Gorge in Africa, and they were particularly common in the Karari Industry, dating to ca. 1.4 million years ago. Retouched flakes were an element of most stone-flaking technologies right up to the recent past.
Retouching was most often applied unifacially, by striking blows against the flake blank’s ventral surface to remove flakes from the dorsal surface. The edge-angle between the ventral and dorsal surfaces is ideal for this. Occasionally flakes were retouched bifacially, to both faces along the one edge. Retouching was usually done by percussion using a hammerstone, although sometimes pressure flaking was used.
Retouching was done for a variety of reasons. Although a stone flake is sharpest when first struck from a core, retouching can repair an edge damaged or worn through use, or gummed-up by the material being worked. Conversely, retouching a razor-sharp edge can steepen it, making it less likely to cut the fingers, so in this case retouching was applied opposite to the cutting edge.