Viscoelastic Behaviour of a Sixteenth-Century Panel Painting: Experimental Analysis and Bilayer Modelling

This research focuses on the analysis of the viscoelastic (VE) behaviour of panel paintings (PPs), which are artworks made of various materials. Each PP is different from others because of their unique assembly, the changes due to the passage of time and human interventions. Thus, a thorough understanding of the hygro-mechanical behaviour of PPs is needed for their conservation. This study analyses the VE behaviour of an original PP from the 16th century, taking it both as a global structure and as a bilayer system. The PP was tested under constant climatic conditions and subjected to a constant load for at least 3 days, followed by a recovery period. The experimental results show that the PP exhibited VE behaviour and that the deformation was recoverable. The PP was loaded at two stress levels, and the results were consistent with the linear VE behaviour expected for moderately loaded wood. The bilayer approach allowed us to separate the contributions of wood and the paint layer, assuming that the latter behaved elastically.