The Winchester hoard under the microscope

On arrival in Scientific Research at the British Museum, the Winchester hoard was studied using a scanning electron microscope (SEM).

The clasp of the small torc is a tube of gold with decoration soldered onto it. High magnification photographs show the beaded wire and pyramids of tiny gold balls (here only 2 mm across) known as granulation.

Although jewellers in Iron Age Britain were very skilled, there is no evidence that they made anything like this or that they knew the technique of granulation. However, goldsmiths in ancient Greece and Rome did. They attached the tiny granules using a solder made from a mixture of copper mineral and glue, heated enough to burn the glue and reduce the copper mineral to metal, which then bonded with the gold. 

Analysis of the gold by X-ray fluorescence spectrometry showed that everything in the hoard was made of gold of high purity. Indeed, it is of much higher purity than the Celtic coinage of Britain and France, and higher than other British jewellery made before the Roman period. The Romans, on the other hand, could and did refine their gold to a high purity.

What can we conclude? These unusual torcs were made with Roman gold by a Roman jeweller. Perhaps they were a gift from Rome to a sympathetic British chieftain, or given as bribery to ensure local support.

Images (from top and left to right): 

Granulation on the small torc from the Winchester hoard (SEM photograph)
Granulation on the small torc (SEM photograph at higher magnification)
The clasp of the small torc
Filigree on clasp of small torc (SEM photograph)