A multi-analytical study of the precious icon “Virgin Hodegetria” (13th century) of the Monreale Cathedral (Palermo, Italy)

The icon Virgin Hodegetria (Fig. 1), now in Santa Maria Nuova Cathedral in Monreale near Palermo (Italy), dates from the beginning of 13th century. Its probable date of execution makes it one of the earliest example of mediaeval icon in Sicily. It has always been considered an icon of William II. The Virgin Hodegetria panel is distinguished from other southern icons by the strong Byzantine matrix and by its size (169 x 131 x 3 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, FT-IR spectroscopy, μ-Raman spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS)). The executive technique appears to be similar to that used in 13th century according to Italian painting tradition: Pieces of linen – impannatura – are present between the wooden support and the gypsum/glue-based preparation layer, in agreement with Teofilo. A characteristic feature of the icon is the use of pastiglia (pastework) to give a three-dimensional effect of some decorations. 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 without bole layer preparation. Mineral pigments (red and yellow ochre, green earth), carbon and bone black, Cu-based pigments, ultramarine, azurite, indigo, orpiment/realgar, lead white, vermillion were mixed with egg-tempera. The presence of several not original paint layers, gilding and varnishes belonging to different previous restorations required a conservation treatment able to give the correct iconography and the stylistic specificities of the masterpiece of Monreale.