Application of multivariate analysis for recognition of organic patinas on stone monuments

Abstract

Black organic films, which had accumulated over ages on stone monuments in ancient villages located in the Apennines in central Italy, were solvent-extracted and the extracts analyzed by capillary gas chromatography. The overall procedure, selection of the monuments and patina extraction followed by chromatographic analysis and processing of the data, was developed with the purpose of establishing a new methodology for clusterization of ancient monuments located in the same geographic area, or even of different parts of the same monument, according to the chemical substances deposited on their surfaces. This concept relies on the assumption that the black crusts present on the monument surface represent a chemical memory of the work of art itself, related to its history, topological location, and exposure to environmental conditions. Selection of the most appropriate extraction solvent, as well as treatment of the chromatographic data, was carried out with the aid of multivariate chemometric methods to obtain classification models.