Diagnostic Survey on Frescoes Paintings in Pompeii by Active IR-Thermography

This paper shows the first results of a diagnostic survey of the fresco paintings in two domus of the Region V in Pompeii, the Domus of C. Iulius Polybius and the Domus of Casti Amanti, which stand out for archaeological relevance and decorative asset. Especially, these cases of study were selected because pose special challenges for damage detection and conservation, due to the presence of large parts of not excavated soil behind walls and frescoes painting surfaces. The survey has been realized within the framework of “The Great Pompei Project” that aims to enhance the effectiveness of the actions and interventions for protecting the archaeological area of Pompeii by developing a special urgent programme of conservation, maintenance, and restoration. One of the main areas of intervention, where this survey is included, is the consolidation and restoration of decorated surfaces. The diagnostic methodology applied in this work is the active thermography by means of an IR thermal camera that acquires the frescoes painting surface emission due to a thermal load applied to the frescoes itself. The measurement has been conducted in reflection mode, i.e. with the camera and the thermal load source located at the same side of the painted wall, the only mode of operation in thick walls as the ancient ones. The survey allowed identifying the main frescoes damages like detachments or delaminations, fissures and moist areas. In this paper, the main problems related to the in-situ measurement by active thermography have been also illustrated and their influence on the diagnostic accuracy quantified. Specifically the issues of uniformity of the thermal load applied to the portion of the frescoes under measurement and the emissivity of its surface were deeply analyzed and their impact to the measurement quality identified