Far Infrared and Raman spectroscopy analysis of inorganic pigments

Few research studies from the early seventies reported the use of Far-infrared spectroscopy and its analytical potential. Especially in the field of cultural heritage no particular attention has been given to this technique due to its destructive character which can be overcome by employing Raman microscopy. However provided that enough sample is available, it may represent a useful analytical method in the case of inorganic compounds which are not active in MIR and, because of the fluorescence effect produced by the organic media, not detectable even by Raman spectroscopy. In this paper the application of Far-IR spectroscopy to the characterisation of several inorganic pigments has been applied. A preparation method based on the use of polyethylene has been developed allowing analyses with moderate quantity of sample (0,5-1,5 mg). The data obtained have been compared to Raman results with the aim to build a common database. Some applications on real case studies are presented and discussed.