Varnishes have been used — or not used — by artists for centuries to create visual effect and provide surface protection. As conservators, we are frequently asked whether a painting should be varnished when it is cleaned or restored. To do this, one needs to evaluate the painting’s condition, understand the artist’s original intent, and be familiar with the history of varnish.
A brief history of varnish: In general, most Western paintings prior to the late 19th century had a protective surface coating of some kind. “But then,” explains John Neuhoff, one of Lowy’s painting conservators, “some of the Impressionists decided they preferred the look of their paintings unvarnished. Couple that with the fact that for a variety of aesthetic reasons many 20th century artists also chose to omit the varnish, and you can see why the decision to varnish a work is not easily made.”
A case-by-case analysis: The conservator must thoroughly analyze the painting to learn the chemical composition of the existing varnish and determine if it can be removed safely. He should ascertain whether (and to what extent) the existing varnish is discolored and see if the painting itself has structural or cosmetic problems that will require removal. The intent of the artist and the general “type” of painting must also be considered. (As a rule, works such as paintings with areas of raw canvas, collage, newsprint or gloss/matte paint combinations should not be varnished.) Reversibility is a concern when varnishing works in acrylic. And of course, the individual artist’s tendency to use varnish should be researched. Armed with this information, the conservator and the client will jointly decide if a new varnish should be applied. “If a layer of varnish will enhance — and not alter — the appearance of the painting, it is usually recommended,” Neuhoff asserts.
Modern varnishing techniques: When a previously varnished painting has been cleaned, it is generally recommended that it be re-varnished with a thin layer of synthetic resin. (Synthetic resins are most desirable because they are reversible and discolor very minimally, even over long periods of time.) “We often wonder,” muses Neuhoff, “if the Impressionists would have felt more favorably about varnish if they had the products we have today.” And after all aesthetic concerns are addressed, there is another issue to consider: safety. “Remember the case of Picasso’s ‘Guernica?’ It was sprayed with red paint by a vandal, but thanks to a coating of a varnish called Acryloid B-72, it was easily restored.”