The consolidation of flaking gouache on Japanese paper

Some gouache works, made in the 1930s by Claude Autant-Lara, were damaged in the paint layer. Extensive areas of gouache including areas of overlapping layers of paint were very cracked. Some of these were even flaking. In order to select the appropriate treatment, we compared the properties of five different strengthening agents, prepared to the same concentration (1%) or same viscosity-(3 cp), resp. Samples of gouache, as close as possible to the work of art were prepared, submitted to accelerated ageing and then consolidated with the strengthening agents: gelatine, sturgeon glue, polyvinyl alcohol, methyl hydroxy ethylcellulose and Paraloid B72. Adhesive and cohesive strength were measured using a peeling test and a shearing test in a traction machine. The different kinds of break and their areas were studied in order to evaluate the particularities of each product and the best one for the case in question.