Can Cellulose Beads Save The Circling of the Planets? Cellulose-Based Consolidating Filler to Stabilise Lifted Brittle Flakes on a Large Painting

Abstract

Augusto Giacometti’s painting The Circling of the Planets (1907; 268 × 218 cm) is in a highly fragile state, suffering from widespread flaking paint. These flakes are very brittle and rigid; none of the usual consolidation techniques managed to achieve necessary ductility to secure lifting paint flakes. In the blue areas, both absorbent protein-oil (lean tempera), as well as non-absorbent oil-protein (tempera grassa) layers were revealed by FTIR analysis. Furthermore, numerous adhesive materials, like wax and PVAc from past conservation treatments, were detected. This paper discusses systematic experiments performed to develop a viscosity-adjusted consolidating filler to secure displaced paint flakes, without mobilising residues of old adhesives or penetrating the lean tempera paint. The properties were controlled to ensure high viscosity, minimal shrinkage, and no build-up of tensile stress, as this could be harmful to the fragile flakes. To apply such a consolidating filler precisely and efficiently beneath numerous detached and lifted flakes, we chose a micro-dispensing system with needles of 0.11 or 0.15 mm diameter that is powered by compressed air. Naturally, the consolidating filler must have sufficient adhesion to both the polar and non-polar materials as found in the painting. Best results were achieved with a consolidating filler composed mainly of methyl cellulose (stable, low polarity), and two new cellulosic filler materials - cellulose beads and microcrystalline cellulose fibres - in combination with pigments. Pigments were included to mask the filler’s whitish appearance and avoid additional retouching.