Characterisation and purification of proteic binders used in easel paintings

Abstract

The easel paintings emerged in the middle ages and since then have been one of the most important art expressions. These paintings are complex systems, with a chemical compositions that change with time, depending on several factors such as the technique followed by the artist; the interaction between pigments and binders; and finally the conservation practices. However the degradation of the original materials, co-presence of different proteins, environmental contamination and precedent addition of restoring materials make this a particularly difficult task to be accomplished. The aim of this work is the characterisation and purification of four animal glues (rabbit, rabbit fur, sheepskin and fish) that are commonly used as binders in easel paintings. In order to complement the glues characterisation were used spectroscopy techniques like FTIR-ATR and µ-Raman; chromatographic techniques namely ion exchange chromatography (IEC) and size exclusion chromatography (SEC); and native PAGE. To determine the organic content, the glues were analysed in terms of proteins, polysaccharides and lipid content.