Preliminary Raman microscopic analyses of a lichen encrustation involved in the biodeterioration of renaissance frescoes in Central Italy

Abstract

Raman microscopic analysis has proved effective in the interpretation and characterization of both the physical and chemical nature of the lichen/substratum system. In the case of Dirina massiliensis forma sorediata, a lichen causing extensive damage to Italian frescoes, the lichen-generated encrustation has been proved to be composed essentially of calcium oxalate. This particular biodeterioration process may be slowed down, or indeed inhibited, by the presence of certain compounds, as yet undertermined, used in the preparation of surfaces and the painting of frescoes. From a conservator's point of view, Raman microscopic analysis uses microscopic samples in the nanogram-picogram range and is non-destructive of the sample.