What question did this study set out to answer?

Investigate deterioration processes of the Arca di Cansignorio della Scala and characterize original decorative features.

June 10, 2026Open Access

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

Puntos clave

Investigate deterioration processes of the Arca di Cansignorio della Scala and characterize original decorative features.
Multi-analytical approach incorporating optical microscopy, environmental scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy.
Stratigraphic sampling and microanalytical investigations of the stone and decorative layers.
Characterization of weathering patterns and mechanical deterioration due to historical restoration attempts.
Three primary weathering patterns identified: marble decohesion, dirt accumulation, and sulphation-induced crusts.
Corrosion of embedded iron bars led to significant structural cracking in the monument.
Original polychrome features and gilding techniques such as azurite and gold leaf applications were characterized.

Resumen

A multi-analytical investigation was carried out to elucidate the deterioration processes affecting the stone materials of the Arca di Cansignorio della Scala in Verona (Italy) and to characterize the surviving traces of its original polychrome and gilded decoration. The study combined macroscopic mapping, stratigraphic sampling, optical microscopy (OM), environmental scanning electron microscopy coupled with energy-dispersive X ray spectroscopy (ESEM-EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and ion chromatography (IC). The monument, predominantly carved from Candoglia marble, exhibits three principal weathering patterns: (i) rain washed areas affected by marble decohesion, (ii) grey deposits corresponding to dirt accumulation areas; and (iii) sulphation-induced black crusts developed in dirt wetting areas. In addition, severe mechanical deterioration was found to be associated with early twentieth-century structural consolidation interventions involving embedded iron bars, whose corrosion-driven volumetric expansion generated vertical cracking. Stratigraphic and microanalytical investigations revealed the presence of original azurite-based polychromy, proteinaceous and lipidic binding media, lead white preparatory layers, and multiple applications of gold leaf. The analytical results highlight the complex interplay between environmental exposure, atmospheric pollution, the incompatibility of materials introduced during past restorations campaigns. Furthermore, they contribute to a better understanding of the composition, execution techniques and preservation state of the surviving decorative layers, providing a scientific basis for future conservation strategies.

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