Varnish has one basic job: to protect your paintings from taking a beating. And it takes this mission seriously, shielding the surface of a painting from such external dangers as fingerprints, small scrapes and scratches, and hazardous atmospheric conditions including moisture and pollution. Some varnishes are also UV-absorbent, which means they filter out the devastating ultraviolet rays in sunlight.
Its an important job, and as long as the varnish is applied correctly, its up to the task. Varnishes are typically thick, heavy fluids made from natural and/or synthetic resins that have been thinned with a solvent. All varnishes are durable, but theyre also formulated to be removable (at least they should be). Solubility is one of the characteristics that distinguishes a varnish from a medium.
Different Types of Varnish
The most popular traditional varnish for oils is damar. This natural resin yellows over time, however, which means it requires removal and replacement more often than its synthetic counterparts. Oil painters also have at their disposal retouch varnish, which is used during the process of painting rather than after. A retouch varnish restores the brilliance of the colors in semidry paint that has sunk into the canvas and lost its intensity. This makes the colors look wet again so you can compare new strokes of paint to existing ones on the canvas.
For pastel, graphite, colored pencil and charcoal artists, there are fixatives. These thin varnishes, which are usually applied by spraying, are formulated for use with dry mediums. Their purpose is to fix the dry particles of medium in place to protect them from smudging or falling off the surface of the artwork. A final fixative is, naturally, the last thing you do to your finished work of art. (Pastelists should take care with final fixatives, because too much can alter the colors.) A workable fixative, on the other hand, is intended to secure one layer of medium in place so you can apply another layer on top of it. Workable fixatives have a rough surface, or tooth, that will hold the next application of medium. However, neither type of fixative will protect the surface from abrasive contact. Thats why all dry-media works need to be framed under glass.
Watercolors, traditionally painted on paper and framed under glass, dont generally require varnishing. If youre painting on Claybord, however, it can be varnished with a fixative made by the surfaces manufacturer, Ampersand. Some artists apply a layer of regular picture varnish over this fixative for added protection and to make it glossy. This is really the only case in which a watercolor need not be framed under glass.
In acrylics, standard mediums are typically used as varnishes as well. Some manufacturers also produce a UV-absorbent varnish formulated differently from any of their mediums. (Remember that varnishes are supposed to be removable, whereas mediums are not.) This is what I recommend if youre concerned with the long-range preservation of your work.
If you choose such a varnish, I suggest that you first coat the painting with a soft-gloss acrylic gel diluted with water. (Use two parts gel to one part water.) This will protect the painting should a conservator ever have to remove and replace the varnish. If youve never used acrylic varnishes, be aware that theyre milky looking and opaque when you apply them. But rest assured, theyll become totally transparent when they dry.
Varnishes can also affect the appearance of your painting. Among other things, a varnish will determine how much the surface of a painting will reflect light. You may have noticed that, before varnishing, the sheen across the surface of a finished painting can vary considerably. An application of varnish will make the sheen consistent throughout the picture. A gloss varnish will deflect much of the light that strikes the surface, thereby giving it a high sheen. A matte varnish, on the other hand, deflects considerably less light, while a satin finish falls somewhere in between. Colors tend to look deeper and richer behind a gloss. (When a glossy painting is properly lighted, you can avoid the glare that disrupts your viewing of the picture.) Matte varnishes push colors back, and so heavily accumulated applications of it can de-intensify your colors considerably. The choice of finish is strictly a matter of preference and depends upon the effect you want.
Tips for Application
There are a few precautions to take before applying a varnish. First of all, dont be overanxious to varnish a work. You may wish to delay this step until youve had time to resolve any second thoughts about your painting. Touch-up painting on top of a varnish can be quite problematic because of weak paint film adherence. It can also be a problem should a future conservator need to replace the varnish: You dont want anything thats integral to the painting to be accidentally removed.
Oil paintings have particular considerations. First, make sure the painting is sufficiently dry before applying the finish. Feeling dry to the touch isnt enoughit can take as long as a year for an oil painting to dry completely, and if you apply the varnish too soon, it could result in cracking somewhere down the line. Second, be certain that your painting is totally free of moisture, including humidity, before you varnish it. If moisture gets trapped beneath the varnish, you can later have a problem with bloom (a cloudlike discoloration), which can ruin a painting. And take care to use the right kind of varnish for your medium. I once inadvertently applied the wrong kind of varnish to a heat-set oil paintingthat was almost a year ago, and the varnish still hasnt dried completely.
No matter what medium you paint in, remember that varnishes can vary from one brand to the next. One manufacturers satin, for instance, may look much like anothers matte. Dont ever try to varnish a work of art if you havent tried the product first. Varnishing is like any other skill: It takes practice. Perform your experiments on test samples before you apply the varnish to an actual painting.
Start with a gloss finish and then, if thats too shiny for you, work your way toward a matte finish until you find the look you want. (The two kinds of varnish are mixable at any ratio you please.) Do your testing over dark colorsthe darker, the betterwhere the results will be most evident. Once youre certain that youre using the right varnish in the right way, youll be able to preserve your works of art for generations to come.
Artist Bart Lindstrom has taught and lectured all over the country, including at seminars for the American Society of Portrait Artists and the Portrait Society of America. He lives in Chattanooga, Tennessee.