Residue analysis sheds new light on old interpretations
Numerous bowl-shaped stone vessels were discovered at Clachtoll
These artefacts have traditionally been dubbed ‘lamps’, believed to have been used like candles
A selection of potsherds and steatite vessels were analysed for the presence of organic residues. This kind of analysis can identify residues from food production, for example, helping us to gain a clearer picture of what people were cooking and eating in the past.
Dr Julie Dunne of the Organic Geochemistry Unit at the University of Bristol analysed 17 potsherds, two surface or ‘burnt-on’ residues from potsherds, five fragments of steatite vessels and five surface residues from steatite vessels.
The results demonstrated that six of the pots had been used to process solely dairy products (milk, butter or cheese). Three other vessels were used to process mainly dairy products but with the addition of some, likely minor, marine resource processing, such as fish or sea mammals. This ties in with the bone evidence since fish bones, seal and whalebone were found at the site. These data suggest that dairy products were an extremely important commodity during this period.
Additionally, the analysis indicated that leafy plants were among the foods processed in these vessels. While all of the vessels were predominantly used to process dairy products, it appears as though most were multi-purpose, also used for marine and plant resources.
A scalpel is used to carefully remove residues from the vessels
A broken vessel discovered among burnt material
The steatite vessels are of a finds type traditionally known as lamps since it was long believed that they were used for this function. Some are bowl-like in appearance while others have a sort of ledge protruding to one side, on which a wick could rest. The results of this programme of analysis contribute to a growing feeling that these ‘lamps’ were not always used for giving light. At least two of the steatite vessels from Clachtoll were used for processing or storing dairy products. This may have been part of food preparation, but it might also represent their use as “butter-lamps”, with a butter-like substance being used as fuel.
Beeswax – another possible source of fuel for a lamp – was identified on one of the steatite vessels, but it was found to be mixed with dairy products. We can only speculate on the reasons for this – but it is possible that a layer of beeswax was layered over the top of a perishable substance (butter, perhaps?), acting as a preservative in much the same way that a layer of fat is used to preserve paté, for example.
This is believed to be the first study of residues on an assemblage of both steatite vessels and potsherds from an Iron Age site in mainland Scotland. The results support previous studies from Iron Age sites in the Northern Isles and southern England, where the evidence suggests that dairying was an important part of subsistence strategies, but as part of a mixed meat/milk economy.
Interestingly, there is no evidence of pig processing in the vessels from Clachtoll Broch, despite the presence of pig bones in the faunal assemblage. This too correlates well with studies from other Iron Age sites, and suggests that pigs may have been processed in other ways – perhaps being roasted in whole joints over the fire rather than being cooked within ceramic or other vessels. Pigs seem to have formed a much smaller part of the Iron Age economy than sheep or cows.
Many thanks to Dr Julie Dunne at the University of Bristol for shedding a little more light on the lives, and food preparation practices, of the people of the broch.
