Characterisation of standard tempera painting layers containing proteinaceous binders by pyrolysis (/Methylation) Gas chromatography mass spectrometry

Thirty standard painting layers were analysed by pyrolysis-gas chromatography/mass spectrometry (Py-GC-MS) and by Py-GC-MS in the presence of tetramethylammonium hydroxide (pyrolysis/methylation). Painting layers were prepared according to Renaissance recipes for tempera, employing proteinaceous binders (egg, glue and casein) and six different pigments. Thermal degradation products of proteins, carbohydrates and lipids were selected for semiquantitative analysis based on single/summed ion monitoring (SIM) mode. The relative distribution of these products was used to characterise binding media for the purpose of their identification in painting layers.