bucket flotation

An archaeobotanical flotation photo gallery

Flotation can also be done manually with buckets, sieves and plenty of water without using electricity or fossil fuels. (see step-by-step instructions or a how-to video). Manual bucket flotation has advantages in being highly portable, cheap and can normally be carried out with locally available materials which can be found in markets in the developing world. While variants exist, a simple wash-over method of bucket flotation is reliable and portable. In this method the sample (or part of it, usually 3-5 litres of sediment) is place in a bucket, water is added, and it is stirred up by hand and clods are gently broken down manually. The water is then further stirred and poured over the lip of the bucket into a receiving sieve (often 0.5mm, although 0.25mm may sometimes be preferred) where the flot is caught. Sand and the heavy fraction remain in the bucket. There is certain amount of skill involved in pouring fast enough to coax out the denser charcoal but not too fast so as to pour out fine sands that might clog the mesh. 


All of the charcoal does not normally come out in the first round of pouring and the therefore the process should be repeated, by adding more water and stirring. The number of times that this needs to be repeated with vary with the quantity of plant remains and clays in the soil, but a s rule of thumb 4 repeats is probably minimal ( and 5 to 6 times recommended). In the final repeat the sediment should not be stirred again but the bucket can be gently rocked to wash over with the action of waves the last remaining seeds and charcoal. The heavy fraction that remains in the bucket can then be emptied onto a coarser metal sieve (of 1mm or 2mm) and is then wet sieved for bones or artefacts. This whole process is repeated again with further sediment until the entire sample has been processed. 

Dr. Eleni Asouti demonstrating bucket flotation to UCL undergraduates.

 

 

The bucket flotation described above is the wash-over method.
(see step-by-step instructions or watch a how-to video on YouTube)

For another description of bucket flotation, of tea-strainer type, (with images), see that of Cheryl Ward, an archaeobotanist in Florida: here

Reference collections. It is also important to explore the modern flora and make modern comparative collections. An introduction can be found in a quick how-to video