Evaluation of defects in panel paintings using infrared, optical and ultrasonic techniques

Abstract

The increasing deterioration of panel paintings can be due to physical processes that take place during exhibition or transit, or as a result of temperature and humidity fluctuations within a building, church or museum. In response to environmental alterations, a panel painting can expand or contract and a new equilibrium state is eventually reached. These adjustments though, are usually accompanied by a change in shape in order to accommodate to the new
\nconditions. In this work, a holographic method for detecting detached regions and micro-cracks is described. Some of
\nthese defects are confirmed by Thermographic Signal Reconstruction (TSR) technique. In addition, Pulsed Phase
\nThermography (PPT) and Principal Component Thermography (PCT) allow to identify with greater contrast two
\nartificial defects in Mylar which are crucial to understand the topic of interest: the discrimination between defect
\nmaterials. Finally, traditional contact ultrasounds applications, are widely applied for the evaluation of the wood quality
\nin several characterization procedures. Inspecting the specimen from the front side, the natural and artificial defects of
\nthe specimen are confirmed. Experimental results derived by the application of the integrated methods on an Italian panel
\npainting reproduction, called The Angel specimen, are presented. The main advantages that these techniques can offer to
\nthe conservation and restoration of artworks are emphasized.