Mechanical properties and moisture-related dimensional change of canvas paintings–canvas and glue sizing

Abstract Understanding canvas paintings as physical systems is fundamental to develop evidence-based environmental specifications for museums. A number of tests were carried out determine mechanical properties canvas, sized with animal glue and glue-based ground layer (gesso) a function relative humidity (RH). The the samples tested exhibited an anisotropy dependent on measurement direction, being stiffness corresponding weft direction greater than warp diagonal ones. Sizing significantly increased its modulus elasticity while was kept in composite material. application system by another order magnitude (~ 2 GPa) whereas material disappeared. measurements wide range RH from 30 90%. An increase caused decrease stiffness. Cracking gesso layer, which often responsible formation cracks paintings, observed at strains few thousandths. Swelling sizing dominated moisture-induced swelling less stiff completely overriding shrinkage untreated canvas. In contrast, stiffer much smaller pure alone, clearly affected textile.