Flotation Method

Soil samples are exposed to gentle streams of water in this water screening device
Soil samples are exposed to gentle streams of water in this water screening device. Kris Hirst (c) 2006

Definition: Archaeological flotation involves using water to process soil or feature fill to recover tiny artifacts. Dried soil is placed on a screen, and water is gently bubbled up through the soil. Seeds, charcoal and other light material (called the light fraction) float off, and tiny pieces of stone called microliths or micro-debitage, bone fragments, and other relatively heavy materials (called the heavy fraction) are left behind.



The original idea to wash soil in this manner was conceived by Stuart Struever at the Apple Hill Hopewell site in the Illinois Valley about 1960, on the recommendations of botanist Hugh Cutler. The first pump-generated machine was developed in 1969 by David French for use at two Anatolian sites.

The Flote-Tech, a single standalone machine to conduct flotation, was developed some thirty years ago, although many archaeologists still prefer to process flotation by hand, using a bucket in a laboratory.

Sources

A bibliography of the flotation method, on its invention and subsequent modifications, has been assembled for this project.

French, D. H. 1971 An experiment in water-sieving. Anatolian Studies 21:59-64.

Struever, Stuart 1968 Flotation techniques for the recovery of small-scale archaeological remains. American Antiquity 33(3):353-362.

This glossary entry is part of the Dictionary of Archaeology.