The diagnostic analyses aimed at the restoration of the mosaic fragment with an angel coming from Giotto's Navicella

The wall mosaic fragment with an angel, subject of this paper, is exposed in the Vatican Grottoes and it comes from the Navicella, a large mosaic by Giotto formerly in the hall of the medieval S. Peter Basilica. For the celebrations of the VII centenary of the death of Boniface VIII the mosaic fragment has been restored; in this occasion a diagnostic campaign of analysis was executed with the aim to study the materials and the executive techniques. The mosaic fragment was investigated through a wide analytical approach. Tesserae and mortars have been investigated through visible, false colour infrared (IRC) and ultraviolet (UV) fluorescence photography and video microscope acquisitions; moreover, XRF has been performed on the glass pastes. Pigments and mortars used in the integrations of the previous restorations have been also investigated through the polarizing microscope (PM) and FTIR analysis of the binders