Hygro-mechanical numerical investigations of a wooden panel painting from 'Katharinenaltar' by Lucas Cranach the Elder

Hygro-mechanical phenomena induced by moisture loading of a historical wooden panel painting from the 16th century are investigated in this study. Due to swelling and shrinking strains resulting from an inappropriate and restraining support frame, damage in terms of ruptures on the painting itself and large curvature have developed. A brief history of the painting and its conservation status are summarised. A two-phase multi-Fickian diffusion model for moisture transport in wood and a consistently coupled hygro-mechanical simulation are applied to explore the influence of different realistic scenarios of climatic change on the panel painting itself and its supporting frame. The hereby gained results can be used to predict the general mechanical behaviour, and help to identify critical parts of the structure and risky climatic situations, which could increase damage. New methods of conservation in terms of innovative stabilising wood frames and adjusted climatic conditions can efficiently be evaluated with the help of the presented approach.