Painted panels belonging to our cultural heritage have been usually subject to complex and rather severe hygromechanical loading in their past history. As a consequence, most of them are cracked and/or permanently bent. The presentation will focus on the generation of permanent deformations, also named "set". Incomplete recovery is observed after wood has been subjected to humidity variations under load. This is a typical manifestation of the mechanosorptive effect, that has been extensively studied in wood rheology although most data relate to the fibre direction and correspond to moderate loading well below the elastic limit. In the case of loading transverse to the grain, which is the situation most commonly encountered in the wood of panels and many cultural objects, the partial restraint of hygroscopic movements rapidly involves critical load levels causing a non linear response of the material.