Flotation and Sampling Strategies
Alys Vaughan-Williams
Picture of system
On archaeological sites, residues of human and animal diet are preserved, along with botanical material from the local environment. Flotation provides the means to retrieve this evidence, and potentially reconstruct the agricultural activities, diet, and trade of that site.
Background to Flotation
Flotation is a method that can used to separate charred botanical material from the soil matrix. Preservation can also occur by waterlogging and mineralisation. Floatation does not work as effectively in these instances, so here we are concentrating on just charred remains.
Where do samples come from?
During excavations, potential sampling sites are uncovered. For charred material, this can be:
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hearths or campfires
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postholes -
Floor sweepings congregate in the corners of rooms.
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floor surfaces -
If a building was abandoned suddenly, material may be scattered randomly on the living surface.
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buildings -
This generally encompasses unintentional burning events, such as fires in the home, or the destruction of a grain store. These contexts preserve some of the best, and most abundant materials.
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rubbish tips -
The identification of certain soil horizons as artifact-bearing can aid archaeologists in providing physical evidence for further testing of other similar horizons.These can accumulate floor sweepings, the remains of hearths, accidental charring events and so on. They do not represent a single event, but a general overview of activities and habits. They are also particularly useful when bones and artifacts are mixed up in them.
To be sampled, a feature also has to be sealed. Effectively, this is like putting a lid on a box, sealing the contents in, and reducing the threat of contamination from either earlier or later material. This could occur through a plaster surface covering an earlier floor, rock tumble, roof collapse creating a protective barrier, and so on.