Integrated Imaging and Spectroscopic Analysis of Residual Polychromy on the Roman Sculptures of the National Archaeological Museum of Formia (LT), Italy

The study of ancient sculptural polychromy increasingly relies on non-invasive analytical approaches capable of identifying pigments and reconstructing original decorative schemes while preserving the integrity of archaeological objects. This paper presents the investigation of the polychromy, extraordinarily preserved, on two Roman marble statues discovered in the forum of Formia (southern Latium) and currently housed in the National Archaeological Museum of Formia: a togate statue (inv. 147614) and a headless draped female figure (inv. 147680). Both sculptures retain exceptionally well-preserved traces of pigments, offering a rare opportunity to investigate materials and painting techniques applied to Roman marble statuary. The analytical protocol combined multiband imaging (Visible-Induced Luminescence and Ultraviolet Luminescence), optical microscopy, Fiber Optic Reflectance Spectroscopy (FORS), portable X-ray Fluorescence (XRF), and Surface Enhanced Raman Spectroscopy (Raman-SERS) applied to two micro-samples. The analyses allowed the identification of Egyptian blue, iron-based pigments, gilding, and an organic red lake on the palettes used for the statues. Raman-SERS measurements provided additional information on the composition of the organic lake detected on the female statue’s himation, supporting its attribution to a natural vegetal-derived dye, as madder lake. The results highlight the success of integrated non-destructive methodologies for the study of Roman sculptural polychromy and contribute to the reconstruction of complex decorative schemes on marble statuary.