This study presents a multi-analytical investigation of two Baroque gilded terracotta sculptures—Hercules and the Nemean Lion (Hercules A) and Hercules and the Lernaean Hydra (Hercules B)—attributed to Lorenzo Vaccaro (1655–1706) and preserved at the Museo Civico Gaetano Filangieri in Naples. This research aimed to reconstruct the original manufacturing technique, characterize materials introduced by successive restoration interventions, and identify active degradation mechanisms. A systematic diagnostic approach integrating UV fluorescence imaging, digital optical microscopy, portable energy-dispersive X-ray fluorescence spectroscopy (EDXRF), Raman spectroscopy, Fourier-transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and spectrocolorimetry was applied. The original gilding system—comprising a ferruginous silico-aluminous terracotta substrate, a calcium sulfate ground, a lead-white imprimitura, an iron-rich bole, and a thin gold leaf—is consistent with documented Baroque mission gilding practices in Southern Italy. Analytical evidence further documented extensive non-original interventions, including copper-based artificial patination, bronze powder (porporina) integration, poly (vinyl acetate) adhesives, and acrylic protective coatings. Raman spectroscopy identified the in situ conversion of intentionally applied tenorite (CuO) to malachite (Cu2CO3(OH)2) as an active degradation pathway. Spectrocolorimetric measurements quantified chromatic alterations of up to ΔE = 52 attributable to accumulated surface deposits. The proposed integrated methodology constitutes a replicable diagnostic framework for investigating gilded terracotta artefacts in museum collections.
Macchia et al. (Wed,) studied this question.