Preliminary Tests of Millimetric Crack Detection in Ancient Wall Paintings using a Terahertz Radar

Fulvia Gennari, Andrea Campostrini, Agnese Babini, Raffaella Lamuraglia, Giancarlo Ruocco, Valeria Giliberti, Arianna Traviglia, Michele Ortolani

Abstract

This work investigates the use of a terahertz radar system for the non-invasive diagnosis of wall paintings at the archaeological site of Pompeii. The imaging system is a frequency-modulated continuous-wave radar with a 27 GHz bandwidth centered at 0.3 THz (wavelength ≈ 1 mm), equipped with a pair of Teflon lenses in a confocal configuration and mounted on a robotic arm for XYZ micromovements. Initial tests targeted visible defects such as cracks and detached paint flakes in order to evaluate system performance. By imaging at multiple focal depths, the radar detected not only surface fractures but also possible subsurface extensions and secondary cracks. Also, THz imaging revealed mold and salt efflorescence with millimeter scale resolution. Although 0.3 THz images do not provide material-specific fingerprints, they clearly reveal dielectric contrasts associated with structural anomalies. Overall, the results demonstrate the potential of THz technology for cultural heritage diagnostics and conservation.

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IMEKO-Metroarchaeo-2025-010.pdf

DOI

10.21014/tc26-2025.010

IMEKO TC

TC26 - Metrology for Cultural Heritage

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