Rubidium hydroxide polyethylene glycol crown ether in the conservation of old master paintings*

The development of new, gentler methods for the conservation of Old Master paintings, with an emphasis on the removal or thinning of deteriorated varnish, is of high priority. In the course of the deterioration process, oxidative attacks lead to progressive formation of carboxylic acid groups, while many ester bondings are expected to be weakened. A stable RbOH polyethylene glycol complex was a promising tool to react with these moieties and to successfully break down the polymeric varnish layer. The remnants were easily wiped off mechanically. Control studies employing (RbOH)-Rb-86 and C-14 polyacrylate showed the complete absence of residual cleansing components on the paint surface.