Archaeobotanical Flotation

Archaeobotanical flotation is the standard recovery technique for charred plant macroremains, separating buoyant carbonized seeds, nutshell, and wood charcoal from archaeological sediment by agitating the soil in water. Because carbonized tissue is light and water-repellent, it rises and overflows into a fine mesh as a 'light fraction,' while denser bone, lithics, and uncharred residue settle as a 'heavy fraction.' The remains are then dried, sorted under low-power magnification, and identified against modern reference collections to reconstruct past diet, agriculture, fuel use, and environment. Machine-assisted water flotation was popularized by Stuart Struever in the late 1960s and systematized for routine paleoethnobotanical practice by Deborah Pearsall, whose handbook codified sampling, processing, and quantification procedures now used worldwide.