The most common type of cleaning required is a surface clean. i.e. removal of surface accumulation of dirt and dust. Discoloured, aged and yellowed varnishes can, if necessary, be removed. This involves the use of stronger solvents and is obviously undertaken with great care in order to avoid "over-cleaning" i.e. removal of the underlying oil paint. A consolidating varnish is then applied to seal and protect the artwork.
Above: Oil portrait of the renowned Shakespearean actress Ellen Tree Kean, painted around 1860, before and after cleaning and restoration.
Varnishing and the rejuvenation of pigments
Oil paints usually consist of earth pigments mixed with either linseed, walnut or poppy oil. Time often takes a heavy toll upon oil paintings and the moisture in the original mix dries out. Sometimes, moisture can enter the paint mix and a whitish "bloom" appears on the surface. These problems can be rectified with cleaning and the addition of a suitable resin-based varnish. This rejuvenates the pigment, giving it a "freshly painted" look, and protects the picture from future deterioration.
Above: These photographs show this painting half-cleaned, revealing the colours beneath the aged and discoloured varnish. Then, finally fully cleaned.
Re-lining
Occasionally, a painting's supporting material (the canvas) can become badly torn, dented or damaged. The paint layer may have become unstable or started to flake. It may therefore be necessary to attach a new canvas to the back of the existing one before starting any other restoration work. This is done using the traditional method of beeswax and resin which consolidates the existing paint layer, enabling repainting and other work to begin.
Above: Oil painting in the style of Thomas Gainsborough(1727-1788), English lansdcape artist and portraitist. I would estimate the date of this picture at between 1760 and 1780, judging by the age of the paint, the style, and the condition and age of the wooden stretcher frame. The canvas around the edges had rotted, causing the painting to become detached from its stretcher frame, thus causing buckling and warping, together with other problems. The painting was re-lined and repainted where necessary to restore it to its original condition.
Patching
This work can normally be carried out from the reverse of the oil painting, with a canvas patch applied of a type matching that of the original as closely as possible. The threads are then carefully aligned on the front, and, after any necessary filling, retouching can commence.
Above: Larpent Roberts painting before and after patching work is done.