In the majority of the literature describing green coloured materials used on ancient painting layers (15th or 16th century), two copper greens are mainly cited: malachite [CuCOr3 x Cu(OH)2] and verdigris [Cu(CH3COO)2 x [Cu(OH)2]3 x 2H2O]. It is shown, by micro-Raman spectroscopy, that the artists were actually employing more than these two copper greens, in particular various copper sulfates, among which the most common pigment found is posnjakite [CuSO4 x 3Cu(OH)2 x H2O]. In contrast to the PIXE (particle induced X-ray emission) technique, Raman spectroscopy is a technique of choice, able to distinguish not only a copper sulfate from a carbonate or acetate but also the different sulfates themselves; in this respect, we found that the high wavenumber region (2800-4000 cm(-1)), characteristic of H2O vibrations, is of particular interest. It is also shown that numerous green areas were created with mixtures of a copper sulfate mixed with other pigments, for instance to enhance the colour depth. Finally, in some cases, no green pigment is actually employed but the colour is obtained by intimately mixing yellow and blue pigments. All these results led to a new look at the pigments which were in use on the palettes of the ancient artists.
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.
Studies on mural paintings from the Tournai Cathedral (Belgium) were carried out by micro‐Raman spectroscopy. The analyses were performed on micro‐samples extracted from the remaining paintings and architectonic decorations, and concerned the pigments, the binders and, in some case, the stratigraphy. The palette was established and various pigments were identified, according to the Romanesque and Gothic periods. Red color was largely made of iron oxides. Lapis lazuli was also found in abundance, mainly on the areas that are assigned by historians to the Romanesque period. The green pigments revealed the use of atacamite and posnjakite. It was also found that some of the paint layers were applied using egg yolk as binding medium. These layers cover the stone above a very thin coating made of gypsum and chalk. The presence of oxalates was often noticed. This can be related to aging due to degradation of chalk by aggressive lichen, but also as result of a degradation of organic substances applied during past restorations. The gypsum is also altered by partial or complete dehydration, thereby damaging the artwork on which the painting is based. In humid conditions, iron oxide could be transformed in its hydrolyzed counterpart, whose Raman spectrum was often observed. Finally, a stratigraphic analysis was carried out on a multilayer fragment from the outside whitewash of the Cathedral, and despite a clear visual difference in morphology, each layer showed surprisingly the same chemical composition. Copyright © 2006 John Wiley & Sons, Ltd.
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