AGEING OF PICTURE VARNISHES MADE WITH NATURAL RESINS

John Cordrey (1755-1825)
Horse, Trap and Groom
oil on canvas adhered to board
Acc. No: 1753

Previous Condition: This picture had been covered with a layer of surface dirt and discoloured, yellow varnish. Previously a canvas on a stretcher, but was at some stage glued onto board. In this process the stretcher tacking margins were cut off. A natural varnish was applied. Extensive retouchings were applied to the sky and small damages were retouched in the darker areas. A final varnish was then applied. Varnishes were applied to enhance the colours of paintings and to protect their surfaces. Unfortunately these natural varnishes yellow and embrittle with age. Today,modern chemistry has improved the quality of conservation varnishes so that they do not discolour and can be removed with mild solvents.

Current Treatment: The removal of surface dirt and yellowed varnish required careful tests to find an appropriate reagent and solvent that would safely remove the layers. Tests were made in areas of the painting to check the solvent’s response in certain colour areas and to see that the integrity of the paint layer was undisturbed. The dirt and the varnish were removed using small white cotton swabs on a stick moving in a circular motion. These were replaced with fresh cotton once they were slightly discoloured. This ensured control during the cleaning process. Small damages were retouched using reversible colours.