Biodeterioration of Acrylic Polymers Paraloid B-72 and B-44: Report on Field Trials

Acrylic polymers have been widely used in the field of conservation since the 1930’s. However, it is becoming increasingly apparent that under certain conditions, these synthetic polymers are subject to degradation through the activities of microbiological organisms. The biodeterioration of synthetic polymers is of particular concern to conservators when used for the long-term protection of archaeological collections and outdoor monuments, where stability with respect to biological attack is of critical importance. At the central Anatolian archaeological site Kaman-Kalehöyük, bronze and other copper alloy artifacts are routinely coated with a layer of acrylic followed by one of wax subsequent to treatment with Benzotriazole (BTA). A severe water leakage in the storage depot at Kaman during the winter of 2003 triggered profuse microbiological growth, and many of the acrylic and wax protective coatings suffered a significant degree of biological deterioration. As a direct result, N. Zaitseva conducted a field study during the excavation season of 2004 to assess the ability of wax and acrylic films to resist microbiological growth in conditions of high humidity. This project is an extension of her research, and will attempt to further characterize the susceptibility of two commonly encountered acrylic polymers, Paraloid B-72 and Paraloid B-44, to biological attack.