Le indagini scientifiche per lo studio e la conservazione dei beni culturali : un approccio analitico integrato, la conoscenza dei materiali costitutivi e della tecnica esecutiva della Madonna Odigitria di Monreale

The icon Virgin Hodegetria, now in Santa Maria Nuova Cathedral in Monreale near Palermo (Italy), probably dates from the beginning of thirteen century could be considered one of the earliest examples of medieval icon in Sicily. The icon is distinguished from other southern icons by the strong Byzantine matrix and by its size (169x131x3 cm). Since 2015, the icon is part of the Arab-Norman Palermo UNESCO Heritage. This paper will deal with historical and scientific investigations on the icon to better understand the painting materials, the executive technique and to resolve question about on-going restoration in planning a complex conservation project. Examination of the icon was both non-invasive (IR false colour, IR b/w, UV fluorescence) and micro invasive (optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, FT-IR spectroscopy and micro-Raman spectroscopy). The executive technique appears to be similar to that used in 13th century according to Italian painting tradition: canvas support is present between the wooden panel and the gypsum/glue-based preparatory layer. The underdrawing includes the occurrence of dark grey accurate lines that seem to have been applied by brush. Silver leaf was used as a background of the paintings and in the haloes of the Virgin and Child without bole layer preparation. Mineral pigments (red and yellow ochre, green earth pigments), carbon and bone black, Cu-based pigments, azurite, indigo, orpiment/realgar, lead white, vermillion were mixed with egg-yolk medium. The presence of several not original paint layers, gilding and varnishes belonging to different previous restorations required a conservation treatment able to return to the original iconography and the stylistic specificities of the masterpiece of Monreale.