During excavation we often take soil samples, particularly if they look like they are going to be full of interesting things such as charcoal and burnt bone, for example. Once the samples have been put into white buckets and given their own unique numbers, they are brought back to our office in Canterbury where the Environmental Team process them.
Each sample is soaked overnight in water containing a small quantity of sodium carbonate, which helps to break down the sediment more easily. Flotation is carried out to separate off the lighter, usually organic, material onto a fine sieve, then the residue is wet-sieved into different size fractions. The residues from the sample are then usually dried, and tiny fragments of bone, fired clay, burnt flint and other interesting materials are separated and weighed. We can learn so much by analysing samples. Burnt grain and animal bones can give us information about diet, for example. Insect remains (on waterlogged sites) and snail shells can tell us about the environment at the time.
Approximately 3.5 tonnes of soil from our site at #InnovationParkMedway were processed, yielding over half a tonne of dried residue. It will be interesting to learn what the samples produce, so watch this space!
All the finds from Rochester were carefully put in bags, labelled with the context number and sent back to our Finds Processing department in Canterbury. Some of the pottery has been dated to the early to mid-Iron Age period and some to the late Iron Age to early Roman. Most of the pottery is flint-tempered, which is often suggestive of prehistoric pottery. A temper is a non-plastic material added to clay to prevent shrinkage and cracking during drying and firing of vessels made from the clay. Crushed flint is ideal for this purpose and flint can easily be found across this area
Finds and sample processing can be a lengthy process, so you never know what will come up in the future from the Rochester collections.
Frances Morgan, Senior Archaeologist