Some Effects of Impregnating Adhesives on Paint Films

Paintings are composed of several layers of various materials. These layers are exposed to outside influences in diverse degrees of intensity depending on their position within the complex structure of the painting. Each layer has its own characteristics which in a well designed paint film have the function of protecting each other from outside influences and their resulting reactions. Thus, the support protects the paint film from the effects of gravity and impact, the sizing protects the priming from the absorbing tendencies of the support, and the priming isolates the paint film from the roughness and color of support. The same analysis can be made starting from the varnish in its protection of the paint film from dirt and atmospheric influences, etc. All these layers are held together by acting adhesive components. Their action and reaction to outside influences is modified by fillers and pigments and other additives. Time and other outside influences change the characteristics of these layers and their effective interlayer adhesives so that they sometimes become unable to further withstand outside stress or stresses caused by divergent reactions of the different layers to outside stresses. The connection between or within the layers breaks, permitting delamination and cracks. The conservators' solution to this problem had been to introduce additional adhesive material into the painting either by local treatment of the affected parts or by impregnation of the whole painting (1, 2). When we see such a painting which has been treated some time ago (usually at a time now undeterminable) we notice deterioration. Is this deterioration due to the treatment, or does it simply show the effects of age? Is it partly caused by the adhesive or possibly by the heat at application? Similar questions can be asked about the cracks. If there existed some machine capable of making time run faster before our eyes so that we could see the effects of age on one part of a homogeneous paint film while keeping another for control, we might be able to answer some of these questions. Attempts in this direction have been made with artificially accelerated aging. However, the aging properties of paint films are so complicated that no satisfactory means of reproducing them