Analysing ancient silver using X-ray spectrometry

What is it about?

Portable or transportable equipment allows measurement of coins and other artefacts in collections and museums, increasing the range of research questions we can address. But are these analyses using transportable equipment good enough? Using 10 coins (analysed more than 1000 times), we compared 5 XRF spectrometers. We found for many elements; * the tube anode doesn't matter so much, * analyses in air were nearly as good as in helium (and are a lot more convenient) * higher voltage tubes are better. With a new understanding of what is in the patinas of silver coins, we used a simple numerical correction to approximate the content of the metal interior. We achieved good results for metals including Cu, Ag, Au, Pb, and Bi.

Featured Image

Why is it important?

Many artifacts are valuable, and all are irreplaceable. Wherever possible, we want to leave artifacts in the same good condition as we found them. Also, many curators of collections are reluctant to let artifacts leave the safety of their collection or museum. If we can analyze new samples non-destructively, at the collection, then a whole range of new research questions can be addressed. Finally, the patina can be a formidable analytical barrier. We use a simple numerical correction which helps to correct for the patina chemistry and gain a more accurate understanding of the artefact interior.