Q. I use two synthetic varnishes (Krylon Matte Finish No. 1311 and Carnival Ultra-Glaze Original Formula) over my oil paintings. Can I remove these varnishes later with mineral spirits or turpentine? Also, can I paint over them?
San Diego, CA
A. Im not familiar with the Carnival Ultra-Glaze Original Formula material, but I can tell you that according to Krylons Web site (www.krylon.com), item 1311 is the companys 11 oz. aerosol can of matte finish. Its recommended for using on glossy photos, negatives, murals and reprints but not for paintings. Instead, Id suggest using Krylons Kamar Varnish, which is reportedly based on a B72 acrylic resin and is often used in the restoration of old paintings. Once dry, most of these varnish coatings cant be dissolved in turpentine or mineral spirits since many synthetic varnishes shift their solubility with age. Removing these varnish coatings requires xylene or toluene, two very strong solvents that can dissolve fresh oil paint films. Although these two solvents are often available at your local hardware store, youre better off leaving the varnish removal to professional conservators since you can easily damage the paint.
In addition, keep in mind that you should never paint over a synthetic resin varnish because the new paint wont be able to bond properly to the oil paint because the synthetic varnish is in the way. Also, if the painting is cleaned of its varnish at a later date, the solvent may soften the lower varnish layer and cause flaking of the upper paint layer.
Ross Merrill is chief of conservation at the National Gallery of Art in Washington, D.C.