Sugar reflotation: An alternative method for sorting flotation-derived heavy fraction samples

Flotation systems cannot always achieve 100% separation of carbonized plant remains from archaeological samples. When soils are especially clay-rich or moist the effectiveness of flotation decreases. As a result, paleoethnobotanical specimens are frequently mixed with heavy fraction remains and require a second stage of processing to isolate them from other artifacts. Although chemical flotation techniques provide one means of separating carbonized plant remains from heavy fractions, these methods can be expensive and frequently require the use of hazardous or toxic chemicals. This paper describes an alternative method of processing heavy fractions using sugar to increase the specific gravity of solution. We use one gallon of tap water 1nixed with 2.5 lb of sugar to form a solution with an approximate specific gravity of 1.11 g/ml. This solution is capable of floating charcoal and seeds, but is not dense enough to float bone, lithics, or fired clay. Using this technique, recovery rates between 96–100% were obtained from samples excavated in the Mississippi Valley of NE Louisiana. Modern plant remains were carbonized and subjected to the sugar reflotation procedure. Results of these experiments indicate that this method does not lead to excessive breakage or damage. The sugar flotation method is in expensive, easy to use, does not unnecessarily harm the carbonized plant materials, and achieves consistently high rates of recovery.