Flotation Flotation is one of our best methods for recovering tiny materials at archaeological sites. Soil from a specific location (such as an ash zone within a pit feature) is dried and then immersed in water. Charred plant remains float and are carefully poured into an ultra-fine screen. When they are all gone, the rest is poured into a separate small screen, yielding heavier items such as animal bone, pottery, and stone. See also light fraction and heavy fraction.