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Experimental investigation of silvering in late Roman coinage

Published online by Cambridge University Press:  21 March 2011

C. Vlachou ,
J.G. McDonnell  and
R.C. Janaway
C. Vlachou
Affiliation:
Department of Archaeological Sciences, University of Bradford, BD7 1DP, UK.
J.G. McDonnell
Affiliation:
Department of Archaeological Sciences, University of Bradford, BD7 1DP, UK.
R.C. Janaway
Affiliation:
Department of Archaeological Sciences, University of Bradford, BD7 1DP, UK.
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Abstract

Roman Coinage suffered from severe debasement during the 3rd century AD. By 250 AD., the production of complex copper alloy (Cu-Sn-Pb-Ag) coins with a silvered surface, became common practice. The same method continued to be applied during the 4th century AD for the production of a new denomination introduced by Diocletian in 293/4 AD. Previous analyses of these coins did not solve key technological issues and in particular, the silvering process. The British Museum kindly allowed further research at Bradford to examine coins from Cope's Archive in more detail, utilizing XRF, SEM-EDS metallography, LA-ICP-MS and EPMA. Metallographic and SEM examination of 128 coins, revealed that the silver layer was very difficult to trace because its thickness was a few microns and in some cases it was present under the corrosion layer. Results derived from the LA-ICP-MS and EPMA analyses have demonstrated, for the first time, the presence of Hg in the surface layers of these coins. A review of ancient sources and historic literature indicated possible methods which might have been used for the production of the plating. A programme of plating experiments was undertaken to examine a number of variables in the process, such as amalgam preparation, and heating cycles. Results from the experimental work are presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 712: Symposium II – Materials Issues in Art and Archaeology VI , 2002 , II9.2
Copyright
Copyright © Materials Research Society 2002

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