Prehistoric pottery

When was the last time you dropped a plate, swept up the bits in a dust pan and put them out with the rubbish? When trying to date a context or feature on an archaeological site, the words 'I need some nice pottery out of that' can often be heard. Why?

Basically pottery is a very useful resource for the archaeologist. First, by its very nature it's brittle but incredibly resistant to decay. Once a pot breaks it is useless to its owner and readily discarded. The pieces of your broken plate can end up in a landfill site and survive as fragments for thousands of years. In the same way broken pieces of prehistoric pottery may well have been used for post hole packing or chucked into a rubbish pit where we can find them still preserved today. The different fabrics and styles of pottery through the ages are well known, and the experienced eye can date fragments (and therefore the layers they are found in) quite easily.

Some of the earliest vessels produced in Britain are the Grimston-Lyles Hill wares. These are generally well made, suggesting a good knowledge of the techniques required. They are shaped like a bowl with a rounded bottom and have a dip, or carination, below the rim. Their design would suit uneven surfaces or nestling in the embers of a fire, with the carination useful for lifting a hot vessel out of a fire with two sticks.

Early pottery was made using clay dug from the ground. To help bind a vessel together, and assist the successful transfer of heat during firing, different fillers or tempers were used. Fillers are particles added to the clay. These can be chips of grit, flint and shell, or organic particles such as seeds and grains. When fired, the organic material is destroyed and we are left with its impression in the clay. These impressions can be very helpful when trying to find out what crops early farmers grew.

Prehistoric pottery is made by the coil method of construction. This is where the sides of a pot are built up, using ring upon ring of clay, until the desired shape is obtained. Early pottery would have been fired in a pit kiln or bonfire kiln. This method is simple and very effective. A shallow pit is dug and lined with sticks, straw and charcoal. The air-dried vessels are placed in the pit and more sticks and straw are packed around them together with other combustible material packed into the pots themselves. The fire is then lit and sealed with more firewood and finally turves. Small air intake holes are left at the sides and an outlet is left in the top.

Though the fire will probably last for only a couple of hours, temperatures of up to 750 degrees Fahrenheit can be reached and considerable heat retained for a whole day. When the kiln is opened pots coloured red will indicate that air has circulated freely during the firing. Alternatively black vessels indicate a well sealed, oxygen free environment.

Different environments can have an effect on the condition of the pottery we find, but as a rule fragments can be very resistant to decay and more often than not, because of the volume produced, the only good source of dating available for a given context short on finds.

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