B. Brunetti

The in situ non invasive methods have experienced a significant development in the last decade because they meet specific needs of analytical chemistry in the field of cultural heritage where artworks are rarely moved from their locations, sampling is rarely permitted, and analytes are a wide range of inorganic, organic and organometallic substances in complex and precious matrices. MOLAB, a unique collection of integrated mobile instruments, has greatly contributed to demonstrate that it is now possible to obtain satisfactory results in the study of a variety of heritage objects without sampling or moving them to a laboratory. The current chapter describes an account of these results with particular attention to ancient, modern, and contemporary paintings. Several non-invasive methods by portable equipment, including XRF, mid- and near-FTIR, UV–Vis and Raman spectroscopy, as well as XRD, are discussed in detail along with their impact on our understanding of painting materials and execution techniques. Examples of successful applications are given, both for point analyses and hyperspectral imaging approaches. Lines for future perspectives are finally drawn.

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 © 2004 John Wiley & Sons, Ltd.