Identification of pigments in the Annunciation sculptural group (Cordoba, Spain) by micro-Raman spectroscopy

A highly flexible method based on micro-Raman spectroscopy was used to examine pigment traces on an Annunciation sculpture group dating from the late Middle Ages. The group comprises a statue of the Archangel Gabriel and another of the Virgin Mary. Both are currently housed in the Archaeological Museum of Cordoba, southern Spain. Information about the pigment palette used by the artists of the time to decorate religious limestone sculptures was for the first time obtained. The pigments found included vermilion (HgS), hematite (α-Fe₂O₃), azurite [Cu₃(CO₃)₂(OH)₂], cerussite (PbCO₃) and anatase (TiO₂). None was directly applied to the sculptures; rather, the limestone was coated with a primer containing calcium carbonate (possibly chalk or half-chalk). The polychromy on both sculptures, which was originally applied in the XV century and seriously damaged in the XVIII, had been treated with an ochre-coloured priming layer of gypsum to make it more uniform and optically similar to the underlying stone.