X-rays shed fresh light on historic coin collection

The University of Birmingham’s Barber Institute is usually regarded as a temple of high culture. Few realise the most hi-tech approaches are sometimes employed to carry out research into the objects in its collections, writes Andrew Davies.

While it is ordinarily the picture galleries that capture the visitor’s attention, the Barber also houses one of Europe’s finest collection of Roman, Byzantine, Sassanian and medieval coins – second only to the Hermitage in St Petersburg, and comparable to that at Dumbarton Oaks University in the US.

Currently, scores of the Barber’s Byzantine coins are being X-rayed as part of an exciting research project to analyse their content.

A collaboration between the Barber and its acting coin curator, Dr Jonathan Jarrett, with Rebecca Darley (former Barber coin exhibition curator) of the Warburg Institute, London, and Robert Bracey of the British Museum, as well as the University’s own Departments of Chemistry and Metallurgy, the project uses X-ray fluorescence (XRF) technology to test the metal content of some of the collection’s Byzantine gold solidi, the so-called ‘dollars of the Middle Ages’.

The new technology, provided by Bruker Industries Ltd, reveal not just gold purity but also the trace elements in the alloy, which may allow the team to spot changes in manufacture and metal sources.

Changes in the composition of the coins often echoed momentous political events such as wars or territorial changes, Dr Jarrett explains, as regimes made the best of what materials were available for the minting process.

‘While the gold standard is supposed to stay the same, at around 97 to 98 per cent, what is changing is the other metals in the coins. We expect to learn more about the minting practice and where the metals are coming from.’

The project is setting new methodological standards for the analysis of coins by XRF. Its conclusions will be presented at the International Numismatic Congress in Sicily in September.

The Barber’s latest coin exhibition, Inheriting Rome: The Imperial Legacy in Coinage and Culture, runs until January 2016. This fascinating show explores how pictorial and design devices that originated in ancient Rome were adopted by subsequent empires and nations – and still hold sway in today’s British coinage.