This paper reports on the diagnostic investigations performed on the bronze panel (a so-called “paliotto”) with high-relief figures inside the Church of San Moisè in Venice (Italy), carried out so as to identify the materials and the causes of corrosion. In particular, both the bulk metal alloy and surface layers (consisting of corrosion products and organic compounds, related with previous restoration actions or original protective treatments) were investigated through a range of microscopic/spectroscopic techniques: the alloy composition and microstructure were determined by VP-SEM/EDS, whilst the corrosion products were analysed by Raman micro-spectroscopy and X-Ray Diffractometry. The organic compounds in surface layers were analysed by Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC-MS). The adjacent mortars were analysed as well, in terms of mineralogical composition and soluble salts content, in order to highlight their role in the degradation processes which took place in the contact areas between the wall and the bronze panel. The results showed that the alloy is a quaternary bronze (Cu-Sn-Zn-Pb): the high-relief figures were cast separately then mechanically joined to the body of the panel. Traces of the clay core were detected in the back of the panel. The bronze surface was artificially patinated by liver of sulfur (K2S). The organic protective layer consisted of stearin and paraffinic wax. However, siccative oil was detected in the layer at the interface with the metal, likely corresponding to the original protective treatment. Also pine resin was detected among the organic compounds. The corrosion products mainly consisted of basic copper chlorides (paratacamite, atacamite) and mixed Cu and Na carbonates (chalconatronite), deriving from the interaction with the surrounding mortar.
C. CHIAVARI, C. MARTINI, S. MONTALBANI, E. FRANZONI, M.C. BIGNOZZI, M.C. PASSERI (2014). The bronze panel (paliotto) of San Moisè in Venice: materials and causes of deterioration. London : EFC (European Federation of Corrosion.
The bronze panel (paliotto) of San Moisè in Venice: materials and causes of deterioration
CHIAVARI, CRISTINA;MARTINI, CARLA;FRANZONI, ELISA;BIGNOZZI, MARIA;
2014
Abstract
This paper reports on the diagnostic investigations performed on the bronze panel (a so-called “paliotto”) with high-relief figures inside the Church of San Moisè in Venice (Italy), carried out so as to identify the materials and the causes of corrosion. In particular, both the bulk metal alloy and surface layers (consisting of corrosion products and organic compounds, related with previous restoration actions or original protective treatments) were investigated through a range of microscopic/spectroscopic techniques: the alloy composition and microstructure were determined by VP-SEM/EDS, whilst the corrosion products were analysed by Raman micro-spectroscopy and X-Ray Diffractometry. The organic compounds in surface layers were analysed by Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC-MS). The adjacent mortars were analysed as well, in terms of mineralogical composition and soluble salts content, in order to highlight their role in the degradation processes which took place in the contact areas between the wall and the bronze panel. The results showed that the alloy is a quaternary bronze (Cu-Sn-Zn-Pb): the high-relief figures were cast separately then mechanically joined to the body of the panel. Traces of the clay core were detected in the back of the panel. The bronze surface was artificially patinated by liver of sulfur (K2S). The organic protective layer consisted of stearin and paraffinic wax. However, siccative oil was detected in the layer at the interface with the metal, likely corresponding to the original protective treatment. Also pine resin was detected among the organic compounds. The corrosion products mainly consisted of basic copper chlorides (paratacamite, atacamite) and mixed Cu and Na carbonates (chalconatronite), deriving from the interaction with the surrounding mortar.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.