Many of the problems in the conservation and restoration of ancient masterpieces are caused by the degradation of the binding medium or the varnish layer. Numerous different natural organic binding materials have been used; therefore, the identification of these materials is of high importance. For the characterisation of binding media with separation methods, such as gas chromatography (GC), liquid chromatography (HPLC) and capilary electrophoresis (CE) generally a large sample is required (typically more than 100μg). Moreover, the extensive sample preparation and the multi-parameter operating conditions make alternative methods desirable. Raman spectroscopy is a nondestructive spectroscopic method, which can be used for the identification of small samples (typically less than 1μg) of the materials used in objects of art, such as inorganic and organic pigments and natural binders and varnishes. The Raman-spectra are a fingerprint of the molecular structure of these materials, which can be used for their identification and for the study of degradation processes. A classification of natural organic binding media and varnishes is proposed which is based on their characteristic chemical functionalities, as revealed by their molecular Raman-spectra. Four major groups can be distinguished, namely the proteinaceous binding media, the resins, the fatty acid containing materials and the polysaccharide binding media.
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