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Old 21-05-03, 08:11 PM
Wislersmum
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Default Varnish Egg Tempera - Which Varnish to Use

Varnishing Egg Tempera Paintings.

This has become a common question for all artists - "Should I varnish my painting?". The answer may depend on who asked the question and who answered it.
Picture varnish has several functions that are often misunderstood. It may protect the painting from scratches, airborne soot and dirt, etc. The protection provided by a varnish may be of ultimate importance to the dealer, collector, or conservator, but for the artist there are other considerations that may well be more important.
The application of a varnish almost always changes the appearance of the painting in two important areas: most varnishes will saturate the paint film, often enlivening the color of the painting and making the darks look darker, it may also add a surface gloss to the painting. These properties of saturation and gloss are most characteristic of natural resin varnishes such as damar and mastic varnishes. But, these varnishes also yellow with age, embrittle, and become cloudy as they oxidize. They may require relatively strong solvent to remove after they age. When added to the paint film, the varnish makes the paint vulnerable to solvents used to remove the surface varnish.
The modern age has introduced "plastic" materials and their complex chemistry.
Synthetic varnishes have been in use for about fifty years and have become common art materials. Generally speaking, the synthetic varnishes provide less saturation, lower gloss, and less yellowing and embrittlement than natural resin varnishes. They are usually soluble in milder solvents. However some of the synthetic varnishes yellow almost as much as natural resin varnishes, and polyvinyl acetate will absorb dirt and grime.
Some 20th century abstract artists used the characteristic effects of varnishes as part of their repertoire of techniques, playing glossy passages off dull and unsaturated parts. Many artists today, following the tradition of the Impressionists do not want their paintings varnished, although rarely does the modern artist understand that the Impressionists objected to the yellowing of the varnish rather than to its gloss or saturation. Other artists object to the gloss and saturation brought out by the varnish, feeling that it makes the painting look old-fashioned. They avoid varnishing their paintings without concern for the protection that the varnish may offer. In the 19th century thick layers of natural resin varnish were applied to almost every painting, hiding the brushwork and, with the ensuing discoloration, obscuring the painting.
To some degree, the varnish application technique controls the final appearance, especially the final gloss of the surface. Varnish that is 'floated' on with a fully loaded brush will result in a thicker, glossier coating than one that is sprayed. Because of their large molecular structure, synthetic varnishes do not saturate as well as the natural resin varnishes, although there are one or two exceptions. Rene de la Rie, Head of the Scientific Research Department of the National Gallery of Art in Washington, developed a synthetic varnish with a short chain molecule much like natural resins but free of the yellowing that comes with age. Like the natural resin varnishes, it saturates the paint film but is soluble in mild solvents, making it the ideal varnish for many paintings, especially oil paintings, where the saturation of the paint may be important. The degree of gloss can be controlled by the length of time the varnish is brushed on the surface while drying. The longer the brushing, the more modest the gloss. Since the varnish formula is in the public domain (the National Gallery is a Federal bureau) Robert Gamblin of Gamblin Artists Colors produces the varnish commercially for both conservators and artists. It is sold under the name GamVar as a two-part system, which the artist mixes prior to application.
When the artist selects a varnish there are several issues that should be considered. What does the artist want to achieve by varnishing the painting? If it is the protection of the fragile paint film, a piece or non-reflective glass might do a better job without the saturation of the paint layer. Does the potential yellowing of natural resin and some synthetic varnish cause concern? A yellowed varnish can quickly destroy the delicate coloration inherent to egg tempera. B72, the synthetic resin in Krylon's Kamar Varnish is a very durable non-yellowing vanish but does not saturate the paint very well. It is also difficult to control the gloss although B72 is easy sprayed. In fact, it comes in an aerosol spray can. B72 requires xylene for removal, which should not pose a problem for a well-dried egg tempera paint film.

HOW LONG SHOULD I WAIT BEFORE VARNISHING AN EGG TEMPERA PAINTING?

I don't know the exact drying time for egg tempera. Treating the egg tempera painting like an oil painting ie. six months to one year for drying, seems like the prudent thing to do. Thin paint films of pure egg tempera might be varnished sooner but egg/oil emulsions should be treated as one would an oil painting. Because the synthetic varnishes can be applied thinly, are flexible, and may be sprayed on, they probably do not require the painting to dry as long. Varnishing your patnting is the final step in a long process of making an egg tempera painting and is important to the final presentation. Choose your materials carefully.

Ross Merrill
Conservator at the National Gallery, Washington.
February 2002
 

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