Year of Botany–Archaeobotany – Institute for Southeast Asian Archaeology (ISEAA)

Flotation Program: Extracting Botanical Samples from Excavated Sediments

The Year of Botany also emphasizes archaeobotany, which is the study of human use of plants in the past through the analysis of ancient plant remains, such as seeds, charcoal, and pollen. Dr. Cristina Castillo of University College London visited the Penn Museum to conduct flotation (see pictures below) and retrieve macrobotanical samples from Ban Chiang sediments that have been stored in the Museum basement for 45 years, ever since they were excavated in 1974-1975.

Flotation is the process of separating soils and dirt from the remains of plants, charred seeds, bones, ceramic sherds, rocks, and whatever else was used or affected by humans. This separation is done by placing the weighed and measured sediment samples on a sieve or cloth placed over a bucket and pouring water over the sample. The dirt is washed into the bucket, leaving the remnants, called a flot, to be dried and examined.

Further separation is done by pouring the flot through increasingly smaller sieves to separate out the larger remains from the smaller, such as seeds.

flot in bucket close-up — close-up of wet flot in bucket

Sediment left over from the flotation process is wet-sieved through a brass mesh to retrieve items like fish bone, sherds, and other archaeological finds.

flot bags drying in the Penn Museum courtyard

The proud flotation crew and organizers, from left: Thitipa Kuttawas, Joyce White, Steve Lang, Cristina Castillo, and Kittiyaporn Sukprasong in front.