Hidden colours in stuccowork damaged by fire: A multi-analytical investigation for revealing the original decorative pattern

The finishes applied on stuccoworks deserves in-depth analytical investigations. A complete chemical and morphological survey is very useful in reconstructing the artist's technique, the history of the artworks through the sequence of the applied layers, and is needed as a basis for any conservation approach. Microscopic observations, both optical and electronic (SEM), and spectroscopic analyses (μRaman, μFTIR and EDS) of gilded and polychrome finishes on plaster relieves, were carried out on 17 samples from a celebrated neoclassical hall in the Royal Palace of Milan (Hall of Caryatids). The original decorative pattern had been damaged during a bomb-induced fire in the Second World War. Most of the surfaces have been fatally compromised and blackened by the effects of the fire. The survey presented here analysed the materials constituting the stucco surfaces and the damage induced by the fire. Green pigments were individuated and mapped, although no green surfaces were visible to the naked eye. It was therefore possible to reconstruct a decorative pattern painted in green, gold and white, similar to traditions of decoration in Austria and southern Germany.