An analytical characterization of different gilding techniques on artworks from the Royal Palace (Caserta, Italy)

An analytical study of the gilding techniques on thirty-eight artworks belonging to the museum collection and storeroom of the Royal Palace in Caserta (Italy) is reported. X-ray fluorescence technique (XRF) was successfully used to analyze the surface layer of the objects and to obtain the main compositional features. Results derived from detailed analyses of the XRF spectra were processed by dendrogram, k-means, graphical clustering, partial least squares regression and principal component analysis. Each gilding technique was characterized. Data on any preparatory layer, on the structure of the gilded object, and on the thickness of the gold foil or leaf used were also obtained. Mercury and oil gilding were identified on brass, copper and ceramic objects, gouache gilding on wood and lead, as well as the absence of gilding and the presence of porporina due to bad restorations. News also emerged on some brass or copper structures that were cataloged as bronze. Furthermore, the thickness of the gold on some objects was estimated using the PLS method. Conservators and restorers will be able to take advantage of these results to update their archives, for the preservation and proper restoration of the artworks.