On shape stability of panel paintings exposed to humidity variations
Part 2: Shape stability of sawn wood

S. Reijnen, A.J.M. Jorissen
Eindhoven University of Technology, the Netherlands

A panel painting is a painting made on a wooden panel. It is not well known, but a lot of famous paintings are actually panel paintings, such as The Mona Lisa by Leonardo Da Vinci, Assunta by Titian, Primavera by Botticelli and Samson and Delilah by Rubens. Artists had clear reasons to choose wood instead of canvas, one of the main reasons was availability and stability. Before an artist could start his painting he had to prepare the panel with several layers of gesso (mixture of glue, gypsum or sometimes ground chalk and water) ossein (lime made from bones) or other materials. After several layers and considerable sanding, the panel surface became perfectly smooth if properly done.

Part 2 discusses the effect of wood moisture changes on deformations. All kind of deformations like cup, twist, bow, etc. (see e.g. figure 8) can be simulated by numerical modelling when taking the wood properties in all directions and the change in properties due to moisture changes into account. Furthermore, for panel paintings, the effect on these deformations of added material like gesso and paint is discussed. The same drying conditions as similar to those considered for the example calculations discussed in part 1: a step from RH = 70% to RH = 30 % . Descriptions of similar studies can be found in literature, e.g. Omarsson et al. – related to the shape stability of sawn wood - and Jakiela et al. – related to painted panels. The purpose of the study described in this part 2 is study benchmarks and to extend the study discussed in part 1