Consolidating the paint layer
The areas of the paint layer that were coming loose exhibited various kinds of damage:
- In the very matt black paint areas, the paint layer contained insufficient binding agent and exhibited minute craquelure. Tiny paint particles (less than 1 mm2) had lost adhesion to the substrate.
- In the more pastose, slightly glossy areas of the picture, such as the background, the paint layer exhibited dishing and was no longer adhering to the substrate in all areas.
Tests were carried out to establish the appropriate consolidating agent in each case and the method of application.
The very matt areas (1) are consolidated using thickened sturgeon glue applied warm over a sheet of Japanese tissue paper and ironed using a small heated spatula and Hostaphan film.
In the case of the paint layers with dishing (2), the consolidating agent (again sturgeon glue) is inserted into the craquelure using a fine brush and, where possible, flattened using the heated spatula over silicone film.
Removal of excess consolidating agent from the surface is carried out under moist conditions, and the surface dirt is removed at the same time.
Small paintlosses were filled with a putty mixture of glue and chalk, then retouched with gouache paints, that dried to a very matt finish. The old and discoloured retouching and overpaint were not removed, but were instead also retouched using gouache paints.
A small publication on the conservation treatment and the 2013 exhibition is available in the Kunsthaus shop.