The Perugino's palette: integration of an extended in situ XRF study by Raman spectroscopy

Throughout the years, a large number of paintings by Perugino have been investigated using the in situ non-destructive x-ray fluorescence (XRF) technique. Three anomalous characteristics were frequently identified, concerning a brown earth pigment containing zinc, the presence of manganese in some red lakes and the association of the presence of copper and tin with grey-blue regions. In an effort to understand these anomalies better, five micro-samples, taken from selected easel paintings by Perugino at the Galleria Nazionale dell'Umbria and a fresco at the Monastero di Sant'Agnese in Perugia, were studied by micro-Raman spectroscopy and scanning electron microscopy (SEM). Micro-Raman spectroscopy was a useful tool to investigate the molecular nature of such uncommon pigments and SEM provided useful information on the stratigraphy of the paint layers. The brown earth pigments, used by the master in the last period of his production, were definitely confirmed to be characterized by zinc impurities. The manganese contained in red lakes was shown to be due to ground alkaline glass, with a small quantity of manganese and iron, probably added to the oil binder in an attempt to speed up drying. Finally, in the sampled paintings, the grey-blue colour characterized by copper and tin was not present. Copyright (C) 2004 John Wiley Sons, Ltd.