Prehistoric pottery experiment hailed a success
By Sigurd Towrie
Story dated: May 24, 2007

The first stage of a project looking at the practicalities of Stone Age pottery came to a conclusion at the weekend.

On Saturday morning, a massive turf-walled “kiln” was lit to test-fire a number of pots created as part of the Orkney Prehistoric Pottery Research Associates (OPPRA) experiment on the making of Neolithic pottery.

Collaborating on the project is archaeologist, Dr Stephen Harrison and Andrew Appleby of Fursbreck Pottery in Harray.

A wood fire was started in the base of the kiln “chamber” at 8am on Saturday morning. Once this had died down, the embers were spread across the base and peat mould added.

Then, the 100 pots were inserted in layers, each layer covered in peat mould until they reached the top of the kiln. A final capping of cow dung was then plastered over the top to "seal in" the heat.

It had been thought that the gaps in the turf wall, and Saturday's strong winds, would be sufficient to create enough draft to heat up the kiln. But by late Saturday evening it became clear that this was not the case.

So additional vents were added to the kiln walls and by 1am on Sunday the internal temperature are reached a more satisfactory 1,064 degrees C. By 2pm on Sunday the first of the fired pots – those from the top layers - were out and cooling (see picture right).

The act of firing the pots destroyed the turf kiln - but even this forms part of the investigation. The turf remains, ash and detritus are to be left to deteriorate naturally and then, in a few years time, will be “excavated” to see what can be learned, or perhaps recognised, in comparison with other archaeological sites and finds in the county.

The creation of the mass of pots has also provided an insight into the techniques used.

It has long been assumed that the prehistoric pots were coil-built, with a long “strand” of clay coiled up on itself to built up the pot walls.

But over 100 pots later, the reality seems different.

“Coiling is not an easy or efficient method of pottery,” said Dr Harrison. “In our experience the best method was to create the pots from a single slab of clay, with the pot walls gradually ‘drawn up’ from the base. This leaves no joins between the base and the walls and no structural weak-points.”

Coiling remains the only option for the larger pots, however. Experiments with these seem to indicate that coils were added to the inside of the vessel and the clay “pulled up” to create the straight walls.

Part of the project is amassing data on the variety of clays available locally. For the test firing, clays from Stacklebrae in Eday and from the Clay Loan in Kirkwall, were used.

Potter Andrew Appleby (left) and archaeologist Dr Stephen Harrison alongside two of the larger replica Neolithic vessels.

Dr Harrison explained: “Although the local clay is not particularly good, some were better than others. Clay from the east, for example, is generally much better than the clays found in the west.

“The Clay Loan clay, for example, was very workable without needing the addition of tempering materials. The Eday clay was of a different quality. It has a very high sand content and we found that the addition of grass cuttings made the clay hold together a lot better and made it much more plastic and workable.”

This variation in clay between the different areas suggests that it may have been a tradable commodity in the Stone Age, with areas of poor clay “importing” better quality material from neighbouring communities.

The pots from the local clay have been fount to be more porous than Andrew Appleby is used to, something he remedies by coating the pots with a layer of melted beeswax.

The initial firing test complete, the team are suggesting that the construction of the kiln was perhaps a communal event. They suggest that the firing, which, for practical reasons, would have been done in the spring or summer months, would have catered for an entire settlement. – perhaps with the winter months spent creating and preparing the pots.

From their experiments, both men hope that, eventually, they will build up a database of various local clays and their properties.

“What we’re aiming for is to get a situation where we can take a pot fragment from any site in Orkney and be able to say where the clay used to make it came from,” said Dr Harrison.

“The project is allowing us to gather massive amounts of data on the clay, pottery techniques and is going to increase our understanding dramatically.”