Considerations on the preservation of ancient wall paintings by using the Infrared Thermography

The long-term monitoring of ancient wall paintings in historical monuments aims to assess the processes of decay involved, clarify the causes, permit plans of intervention and at the same time control the effectiveness of the restoration works. The paintings are prone to degradation over time. Their decay can arise from humidity, heat transfer, ultraviolet radiation, atmospheric pollutants, microbial agents, bad display or storage conditions, and even physical vibrations. This paper proposes a procedure for analyzing the state of preservation of the frescoes, which also takes into account the state of the walls on which the frescoes are located, the degradation of which has a considerable influence on that of these artistic works, in order to plan any useful restoration work. While the state of frescoes can be evaluated by means of the non-intrusive technique of passive infrared thermography (IRT), the state of the hosting walls can be studied by a quantitative IRT approach(QIRT), which allows a more accurate evaluation. The authors in particular propose an approach based on the estimation of the uncertainty of the measurement of changes in time of the parameters observed through the infrared thermography to more opportunely determine the state of conservation of frescoes and ensure higher reliability in the evaluation of the degradation status over time.