Deterioration Processes of Stone Materials and Polychrome Findings on the 14th– Century Arca of Cansignorio Della Scala Monument in Verona

A multi-analytical study was conducted to investigate the deterioration mechanisms affecting the stone materials of the Arca di Cansignorio della Scala (Verona, Italy) and to identify the residual traces of polychromy and gilding. The investigation combined macroscopic mapping, stratigraphic sampling, optical microscopy (OM), environmental scanning electron microscopy (ESEM) coupled with energy-dispersive spectroscopy (EDXS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and ion chromatography (IC). The monument, mainly carved in Candoglia marble, exhibits three principal weathering typologies: (i) meteoric washing associated with marble decohesion, (ii) grey deposits (dirt accumulation areas); and (iii) sulphation-related black crust formation (dirt wetting areas). In addition, severe mechanical damage is as-sociated with early 20th-century structural consolidation using embedded iron bars, whose corrosion-induced volumetric expansion generated vertical fissures. Strati-graphic analyses revealed the presence of original azurite-based polychrome, proteina-ceous and lipidic binders, lead white preparatory layers, and multiple gold leaf applica-tions of gold leaf. The study highlights the interaction between environmental exposure, atmospheric pollution, material incompatibility resulting from past restorations cam-paigns, and the preservation state of the surviving decorative painted layers.