Brown, Katherine Louise; (2002) Raman microscopic and computational studies of artists' pigments and molecular inorganic compounds. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis is principally concerned with spectroscopic and computational studies of artists' pigments. Manuscripts, art and archaeological artefacts were examined by Raman microscopy, identifying the pigments and drawing conclusions for historical and conservation purposes. Studies of Anglo Saxon and later manuscripts have shown the Insular palette triumvirate, assumed to be orpiment, red lead and verdigris, to contain red ochre and vergaut, but no verdigris. This remains unchanged until the introduction of lazurite in C.920 AD and vermilion in the 12th century. Lazurite has been erroneously identified on the Lindisfarne Gospels, by the technique of Roosen-Runge. Raman microscopy shows the blue pigments to be exclusively indigo, casting doubt on analyses performed using Roosen-Runge's technique. The Islamic manuscript palette was found to be remarkably consistent across a substantial geographical area over an extended period. It is also very similar to that of early Western manuscripts. Comparison of these results with existing literary sources has shown the latter to be highly inaccurate. The palette of William Blake was examined and compared to results of analysis by False Colour Infrared Photography (FC-IP). The FC-IP technique was determined to be inappropriate for pigment identification. Two significant artefacts were shown to be modern forgeries: a rare Assyrian fresco contains a modern green pigment, and the world famous Vinland map was found to have significant quantities of anatase in the yellow lines. Density Functional Theory methods were applied to the mechanism of decay isomerisation of AS4S4, which was partially clarified, and to the geometries of R2SeX2 (R = CF3, CF2H, CFH2, CH3, CH2CH3, CH(CH3)2, t-Butyl, X = F, Cl, Br, I, At). The most stable geometry was found to be determined by the polarity of the Se-X bonds and the steric and electron-withdrawal effects of the R-group on the C-Se bond strength.

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