Active and Eddy Current Pulsed Thermography to Detect Surface Crack and Defect in Historical and Archaeological Discoveries

The present paper describes the results of an experimentation concerning the joint use of active thermographyand eddy current pulsed thermography to assess the conservation state of historical and archaeological discoveries.The preservation of historical and archaeological heritage is today an open issue due to the amount offinds and to the costs of the current methodologies and technologies used. As a consequence, interventions aremade only when a deterioration process is in progress. The use of non-invasive techniques is essential for suchapplications in order to not compromise the integrity of the find.Thermography has been used to measure the thermal response of a metallic historical artifact (an iron oillamp) during the application of thermal solicitations. The authors propose the use of a hybrid technique combiningthe standard active thermography with the eddy current pulsed thermography. This hybrid technique isnon-invasive and contactless and allows to detect surface cracks and defects which are not visible at naked eye.Results have shown clearly how the proposed thermographic technique allows to improve the effectiveness ofthe standard techniques to detect surface defects. The defects are more easily detectable because of the moreaccentuated contrast and better resolution of the thermographic images. The final aim of the paper is to describehow this improved technique can be used to diagnose, monitor and preserve the conservation state of historicalor archaeological discoveries.