Flaking Paint on Absorbent Canvas: Approach, Possibilities and Challenges

One type of degradation commonly observed with paintings on absorbent canvas is flaking paint. Solutions to this degradation phenomenon are particularly challenging and the search for an ideal one - an on-going one. This paper reviews and summarises approaches that have developed over the past decade at the Bern University of Applied Sciences.
The goal set is to obtain a thin adhesive film or preferably a network of thin adhesive bridges between the adherends, but without penetration of either canvas nor paint flake. The catalogue of requirements for the adhesive is drawn up after an examination of the two substrates with respect to the most important criteria: solubility, porosity, accessibility and ageing behaviour of the applied medium. An adhesive medium is thus chosen based on these requirements, its application method and its film formation principle. Since each binder exhibits specific properties that must be taken into account during application and drying, it is essential to consider both processes and materials as an interacting system. Relevant techniques of application are presented based on exemplary use of the following adhesives: methylcellulose, gelatine, sturgeon glue, hydroxypropylcellulose and acrylate dispersions. Special attention is given to the important technique of "masking". Furthermore, an approach to visually qualify and assess both distribution and penetration of the adhesives by employing fluorochromes as a tracer is presented. Finally, some special cases of adhesion fillers and variations for liquid applications are introduced.