Micro-Raman spectroscopic analysis of different species of copper sulfates was carried out. Products such as antlerite, brochantite, posnjakite, langite and chalcanthite were investigated. These products are most likely to be formed as the result of atmospheric corrosion of copper alloys, e.g. bronze in sulfur-bearing environments. A database containing the characteristic Raman spectra was set up. This database was then used to investigate some specimens of copper alloy artefacts, that had been exposed to the atmosphere. It was shown to be possible to identify the nature of the corrosion products formed, using micro-Raman spectroscopy.
XPS analysis of different forms of copper sulfate, including antlerite, brochantite, posnjakite, chalcanthite and anhydrous copper sulfate, as well as pure copper and its oxides cuprite and tenorite, was carried out. These products most often occur when dealing with atmospheric corrosion of copper and bronze in sulfur-bearing environments. These compounds were minerals, commercial products, or grown on pure copper by artificial weathering. Spectral features such as peak energy and line shape for Cu 2p, Cu LMM, O 1s and S 2p bands were examined. Comparison of the measurements obtained proves the efficiency of XPS in differentiating the various compounds.
Artificial patination is mostly based on empirical recipes for which the result is difficult to forecast. Little is known about the final corrosion compound formed on the patinated object. Therefore, different patinas based on copper nitrate -an ingredient recurrent in numerous references -were realized according to traditional recipes. Their characteristics of morphology and molecular composition were studied using various methods such as scanning electron microscopy (SEM)-energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and Raman spectroscopy (RS). A better understanding of artificial patinas will not only allow developing appropriate methods of conservation and restoration, but also differentiating between natural and artificial patinas. An example of a patina present on an ancient artifact is discussed and compared with the studied artificial patinas.
Micro-Raman spectroscopy was used in combination with other analytical techniques for the in situ study of a Persian Herati lacquered manuscript dated 1530 AD. The text is calligraphied on sized and polished folios, framed in papers tinted in various shades and sparkled with gold leaf, according to a specific gilding technique. The palette of pigments used for the illumination, the coloured frames and the cover was established. Lead white, amorphous carbon, lapis lazuli, red lead and cinnabar were unambiguously identified. The green bottom layer of the lacquer decoration appeared to be composed of mixed orpiment and lapis lazuli. Another green pigment present in the illumination could not be identified although a Raman spectrum was recorded. In order to determine the composition of the different elements of the cover and regions realised with the Marqash technique, complementary analysis was carried out, using x-ray photoelectron and x-ray fluorescence spectroscopy. The results obtained by these analyses can be put in parallel with the Arabic treatises describing the realization of these manuscripts from Persian workshops.
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