CONSERVATION: Up Close
‘As white as snow’ – a treatment example
Examined and prepared for display by the Gallery's painting conservator
- Dr. Maria Kubik
Charles Daubigny painted Snow Scene Valmondois in 1875 using oil paints onto a primed linen canvas. Since its acquisition in 1904, the painting had undergone several restoration treatments, including tear repairs in 1952, lining onto a secondary canvas in 1961, and retouching of scratches in 1974. Required again for display in the Wonderlust Exhibition, Snow Scene was examined and prepared for display. During this examination, the extent of yellowing of the thick dammar varnish layer became apparent. Tests to remove varnish along the painting's edge, normally obscured by the frame, were successful, and cleaning was extended to the rest of the painting.
During treatment, 8/9/08. The colour of the snow and sky changes dramatically as the obscuring yellow varnish is removed.
The Gallery’s paintings conservator, Dr Maria Kubik, applies solvents under a fume extraction unit.
During treatment, 2/10/08. Nearing completion of the varnish removal.
Cleaning a painting
Cleaning a painting is a painstaking process, requiring small cotton wool swabs and solvent gel formulations. The solvents must be tested to ensure they only affect the varnish layer, and not the paint below. The solvent gel is applied using swabs, and the varnish is slowly removed. The result can be quite dramatic, with the painting becoming brighter with every step.
Once cleaned, the painting’s earlier overpaintings had to be removed, as these had also significantly discoloured. An isolating varnish of synthetic resin was applied, over which retouching could safely be performed. This will allow the retouching to be removed in the future. Similarly, five birds which the artist had originally painted over became more visible once the varnish was removed. This is due to oil paint becoming increasingly transparent as it ages, sometimes revealing unintentional details below. Such original overpaintings by the artist are known as ‘pentimenti’, and may be detected by Infrared or X-ray imaging. As the artist would not have intended these birds to be seen, a decision was made to again cover them. The new paint was applied to areas of loss only, using a stable, reversible material.
As oil paint ages, it becomes more transparent. Several birds overpainted by the artist (circled in red) were visible through the mist. Following cleaning, these were again covered using reversible retouching paints.
After treatment and replaced in its frame.
To finish, a new varnish layer was applied consisting of dammar and a hindered amine light stabiliser. This combination replicates the look and feel of the original, while extending the life-span of the new coating.