In archaeology there are several methods of collecting and processing data and a lot of them can be performed in the lab. Sometimes, however, there is a need to do what is called flotation (click on this link to see a short video of flotation using a commercially-made tank); this is when a sample is put into a deep screen which sits inside a tank that is being pumped with water from below the screen.
Flotation tank set-up (photo by Abigail Hyndman).
As the water flows, the sample gets stirred and swished by an archaeologist
Archaeology stew (photo by Abigail Hyndman).
and the light “fraction” (artifacts and particles that float) floats to the top of the screen and spills out a spout onto a smaller screen along with the water that has overflowed.
Water pouring out of spout (photo by Abigail Hyndman).
This leaves us with all of the tiny artifacts on one screen (light fraction), and all the larger and heavier artifacts still in the big screen (heavy fraction). The reason why we do this process is so that we can be sure that we’re seeing things as small as seeds or tiny bits of charcoal within a sample. These things are often washed or screened away without the use of the flotation tank.
Right now, MTSU Anthropology majors Mimi Glass and I (Abigail) are working on using this method on samples from last summer’s excavations at Site 40DV7. When we started there were over fifty samples that needed to be processed and now we are close to being finished. Within these samples we’ve seen a lot of charcoal, tiny pieces of shell, small lithics, and even some small bone fragments. It’s dirty work but very rewarding as you watch a big bag of dirt turn into small archaeological finds that will yield big data!
Guest post by Abigail Hyndman
(Many thanks to the Tennessee Division of Archaeology for allowing us to use their flotation equipment!)