Varnishing oil paintings

24 Feb 2009

Q: How often do I have to varnish an oil painting? How do I clean the painting before I apply new varnish?

A: A final coat of varnish—on a finished and completely dry oil painting—can last hundreds of years. Sennelier makes two kinds of varnish for works in progress, one of which is called Turner Touch Up Varnish, which dries quickly. It is designed for restarting an oil work on a dry base and to correct for sinkage. It can be thinned with turpentine or mineral spirits. The other kind of varnish is also called Touch Up Varnish but includes an alcohol base. It is a clear, synthetic resin that does not yellow, dries quickly, and can be thinned with alcohol. It is recommended for professionals and art restorers due to the delicacy with which it can be used.

If you are cleaning your own painting, I assume that the painting has accumulated layers of environmental residue. Do not use any soap solution because this can damage your painting. If moisture gets under paint, it will create a bloom. If your painting has any mold, exposure to strong sunlight (or ultraviolet light) and fresh air usually destroys it and stops its growth. You can also use a water-dipped cotton swab in a gentle circular motion to clean small areas of a painting.

--by Camille LaPointe-Lyons

Q: What is the best process for applying varnish to a large oil painting? Should I apply a retouch varnish to protect the painting until it is time to apply the final varnish?

A: Touch-up varnish keeps the paints unified while you are working on a painting. It will mask sinkage, brighten colors, and provide an anchor for fresh paint when resuming a work that has already dried. Touch-up varnish should be used on only the small area of the painting that you are working on. Once your entire painting is complete, it can be applied in a thin coat as a provisional varnish until your painting has completely dried. This will take six months to a year to cure, and then you can apply the final varnish. There are two types of touch-up varnish: solution varnish, thinned with alcohol, and cooked oil varnish, thinned with mineral spirits. Final oil-painting varnishes should only be applied to completely dried oil paintings, and the paints will take a year to completely cure. You will also want to consider whether you want your varnish to have a matte, satin, or gloss finish. Be sure to paint thin layers of varnish on the painting with a very broad, soft bristle brush, and keep the painting almost flat to prevent beads of varnish from running across your painting.

--by Camille LaPointe-Lyons


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