Q. Is it safe to varnish traditional egg tempera paintings and, if so, which varnish should be used? What about nontraditional egg tempera—a mixture of acrylic paint, egg yolk, retarder and acrylic flow release medium?
A. Varnishing a traditional egg tempera painting is usually not recommended. The varnish tends to saturate dark passages of the painting, causing any over-painting or corrections to show through in an undesirable way. Usually, egg tempera painters merely polish the surfaces of their well-dried paintings using a very soft, lint-free cotton cloth, a piece of silk or old nylon stockings. They then frame the paintings behind glass to protect the fragile surfaces.
Your non-traditional egg tempera shouldnt be called egg tempera at all: Its really an acrylic emulsion paint with egg yolk added.
I cant recommend these complicated recipes because theres no way to predict the long-term consequences of using them. You could simply leave out the egg yolk and paint with the acrylic emulsion paint in imitation of the egg tempera technique, using translucent layers of color. I also recommend that you limit the use of the retarder. You can easily use too much and make a paint that doesnt dry properly. Instead, thin the paints with an acrylic emulsion matte medium and a little water.
If the painting has an uneven gloss when youre finished, give your work a light coating of acrylic emulsion gel medium thinned with water (two parts medium, one part water). Once this is dry, varnish the painting with an acrylic solution varnish, either matte or glossy.
Doug Dawson, a pastelist in Colorado, has taught landscape and figurative painting workshops for more than 20 years, including classes at the Art Students League of Denver.