This article is part of the Journal of Raman Spectroscopy special issue entitled ”Raman spectroscopy in art and archaeology“ edited by Juan Manuel Madariaga and Danilo Bersani.
Raman investigation of artificial patinas on recent bronze – Part I: climatic chamber exposure†
Article first published online: 18 SEP 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Special Issue: Raman spectroscopy in art and archaeology
Volume 43, Issue 11, pages 1578–1586, November 2012
How to Cite
Ropret, P. and Kosec, T. (2012), Raman investigation of artificial patinas on recent bronze – Part I: climatic chamber exposure. J. Raman Spectrosc., 43: 1578–1586. doi: 10.1002/jrs.4068
- Issue published online: 21 NOV 2012
- Article first published online: 18 SEP 2012
- Manuscript Revised: 2 MAR 2012
- Manuscript Accepted: 2 MAR 2012
- Manuscript Received: 12 DEC 2011
- artist's patina;
- chemical patina;
- Raman spectroscopy;
- climatic exposure
In humid air, copper and its high copper alloys (bronze) tend to form an oxide layer (patina). Natural patinas protect copper and its alloys from further corrosion processes. On the other hand, artists have frequently deliberately patinated bronze for visual effects. Thus, it is of great importance to study the patina changing mechanism to follow its chemical changes and to predict in advance the likely corrosion processes. Green chloride and green nitrate patinas, applied over the brown artist's patina, were tested, and also brown patina and the patina that develops on bare bronze. The Raman spectra were studied after chemical patination, and after exposing the patina samples in a climatic chamber, which can produce an environment that resembles an industrial atmosphere, for 12 weeks. The structures of the patinas and of the corrosion products were characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction. Cuprite and cuprous sulfite were found on the brown patina, atacamite on the green chloride patina, and a mixture of gerhardite and rouaite on the blue to green nitrate type patina. After 12 weeks of exposure to humidity, a controlled concentration of SO2, and salt spray mist, the corrosion products changed. In general, clinoatacamite and paratacamite are the end corrosion products, after an intermediate brochantite stage on the green chloride and green nitrate type patinas. The end products of each patina type are given. Copyright © 2012 John Wiley & Sons, Ltd.