Raman and SEM‐EDX analyses of the ‘Royal Portal’ of Bordeaux Cathedral for the virtual restitution of the statuary polychromy

Abstract

The chemical analysis of the remains of paintings from the Royal Portal of Bordeaux Cathedral was carried out by in situ analytical techniques and by laboratory techniques after sampling. Even though, nowadays, portable systems have a good performance and provide reliable results, in the present case, the in situ approach failed, and the analysis had to be carried out in the laboratory. The obtained results were used to propose a virtual restitution of the polychromy and to have an idea of how this portal was when it was built in the XIII century. During the analysis, the degradation process of pigment azurite was studied through the determined decay products, such as copper oxalate (moolooite) and copper basic sulfate (brochantite). This degradation seems to occur because of the presence of oxalic acid in the chemical system, as other calcium oxalates (weddellite) were identified as a degradation product of calcareous support. Copyright © 2015 John Wiley & Sons, Ltd.