Thursday, October 20, 2016

Floating the Organic Material

My name is Austin George and I am one of the three lab interns this semester. I was a student in the field school in 2015 and I was also the lab supervisor this summer during the 2016 field school. I am currently a junior at Western Michigan majoring in anthropology and minoring in geography. This summer during the project, the students had many great experiences with archaeology while they learned how to dig, screen, and clean the artifacts. The one thing that had to wait until we got back to Western was doing our flotation samples. The point of a flotation sample is to float all of the organic material and find as much evidence as we can.
Dr. Nassaney shows Tommy and me how to use the flotation machine
(Photo by author)
When we use the flotation machine we float large bags of dirt that the students would have dug out of their units during the summer months. They start by measuring out a box in their unit to a size that best fits the shape and objects that they have found while digging. They then dig it out to get 10 liters of dirt that they place in a flotation bag that gets sent back to the university. At the university, we have a large metal machine called the float tech machine. When we use the machine, it gets filled with water and there are two screens. The dirt gets poured into one side of the machine and the water pump gets turned on which pumps air and water into the dirt. As the water rises the organic materials like burned seeds and pieces of charcoal float to the top of the water. It then pours over a small wall in the middle and onto another screen where all the materials are collected on another small screen. When all the dirt has been removed and all the organic material has been collected in the screen, we remove the light fraction (burnt seeds, roots, and charcoal) screen and set it out to dry. We then remove all of the heavy fraction materials like glass seed beads and bones. These samples are also set aside to dry for a week or so. The machine was really intricate but yet it was very simple at the same time. The hardest part was having to pump out the dirt by hand so the motor wasn’t damaged. The next step in the process is to sort through all the material with a large magnifying glass so that we can see all the tiny seeds and materials that can give us more information about the fort. So far just by looking with the bare eye we can see a lot of glass seed beads, bones, and a piece of a lead seal. Hopefully when we go through them we can find a lot of organic material that will help us answer questions we may have
The lead seal fragment we found while doing flotation samples
(Photo by author)