As oil paint ages, becoming more brittle and less able to accommodate movement and distortions in the support. The physical properties of each material layer vary with changes of temperature and relative humidity. Since each layer responds differently, stress occurs and damage may result.
The ancestral portrait of John Willison Hutton, Right Worshipful Master of masonic Lodge St. David 78 (Dundee), 1863-5, was technically unusual, consisting of oil on two layers of paper with a fabric backing placed on a wood stretcher to simulate the appearance of a canvas painting. The fabric backing was degraded and required removal, which also allowed access for treatment of the tears in the paper layers.
The portrait’s treatment included removal of the degraded fabric backing, repair of the tears in the paper support, cleaning, and inpainting of paint losses.
The painter of this ancestral portrait has not been identified but it remains in family ownership. Previous restoration included “lining” (glueing of the painting to a secondary textile support). Complete removal of some mild corner deformation in the stiff, lined canvas was not possible.
Removal of the amber-coloured film was accomplished through surface cleaning alone. Yellowish discolouration may indicate the colour of a a surface dirt layer and/or the presence of a yellowed varnish layer. Paintings displayed in smoking environments frequently develop a yellowish cast as the by-products of tobbacco smoking are gradually deposited on the surface. During examination, the conservator determines the nature and cause of discolouration, and then will advise if surface cleaning or surface cleaning and varnish removal are required.