The varnish is a protective transparent surface coating composed of a natural or synthetic resin. Within the stratigraphy of a painting, the varnish has severals functions : saturate the colours, protect the paint layer against small superficial scratches ; absorb the uv radiation harmful for the pigments and the paint medium and binder ; and prevent the dirt to penetrate into the paint layer.
The aging process generates the oxydation of the resin. This oxydation becomes observably due to the darkening or yellowing of the coat. The tint taken by the varnish can be yellow, brown or in some cases even blackish. This veil tampers with the perception of the colours and tarnishes the contrasts. Other deteriorations such as the blanching or the crazing can appear in a varnish coat influencing the readability of the composition.
Before intervening, we conduct pre-tests, defining the most adequate mixture of solvents and applying technique for a save removal of the varnish without jeopardise the original paint.