Experimental Study to Assess Micro-mechanical Behavior of Oil Paintings over Time

The majority of oil paintings in museum collections suffer from various chemo-mechanical degradation phenomena. Oil paint is generally made up of layers of drying oil (binder) and metal-based pigment particles. One of the most important degradation mechanisms in historical oil paintings is metal soap formation. Metal ions released by the pigments interact chemically with the saturated fatty acids present in drying oils to form metal soaps. Metal soaps can develop into big aggregates, which deform paint layers and may cause mechanical damage like flaking and cracking of the paint. Additionally, the mechanical response of oil paint shows a strong dependence on age, influencing mechanical properties such as toughness, stiffness, and ductility. The interaction between metal soap formation and the aging response of oil paintings ultimately affects their degradation response. With the help of cutting-edge micro-mechanics experimental techniques, this study aims to identify the causes of changes in the chemo-mechanical response of oil paintings over time.