Application of SIMS to silver tarnish at the British Museum

The tarnishing of silver in a museum environment is a perennial problem. Silver reacts with atmospheric gases generating a thin disfiguring surface layer. In order to elucidate the nature of the tarnish layer formed in showcase environments in the British Museum, a number of silver coupons were exposed in different situations inside showcases. SIMS analysis with the Millbrook Chemical Microscope has identified a number of compounds within the tarnish layers. It has indicated a much more complex composition than the silver sulphide commonly associated with silver tarnish.