Varnishing: The Final Step in the Painting Process
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- April 18, 2018
- Ed S. Brickler
Varnishing: The Final Step in the Painting Process
By Ed S. Brickler
It doesn’t matter how many hours it took to complete that painting, the final step in the creative process is to protect your creation with varnish in order to protect the paint film. Varnish consist of a resin diluted in a solvent, and when the solvent evaporates it leaves a protective film of dried resin on the surface protecting the paint film. A varnish is different from an oil medium since the oil medium also contains a drying oil such as linseed, safflower, walnut or poppy oil. No oil medium of any kind should ever be used as a final varnish.
Why Varnish?
As the oil paint film dries through oxidation it tends to shrink. Without varnish, any dust, dirt or atmospheric residue on the surface would become part of the paint film causing discoloration. Varnishing helps even out the sheen, enhancing the appearance of the paint film. All varnishes should be reversible, meaning they can be removed in the by a conservator to clean the painting.
Types of Varnish: Traditional Varnish versus Modern Varnish
The following are the many differences between a traditional varnish and a modern varnish:
1) Traditional varnishes are made with natural resins such as Dammar, Shellac, Mastic, Sandarac, Colophony and Copal. On the other hand, modern varnishes are made with synthetic resins such as ketonic, acrylic (mineral spirit acrylic) and other similia synthetics.
2) Another difference is the solvent used to dissolve the resin. Most of the traditional resins are no longer used but Dammar remains as the most common traditional varnish and is made with a Dammar resin. Dammar is soluble in turpentine. On the other hand, modern synthetic resins are soluble in mineral spirits.
3) A big difference between traditional and modern varnishes is what happens to them when they age. Dammar has a tendency to yellow and become brittle with age and therefore should not be applied too heavily. Picture Varnishes are made with modern resins which are more flexible and do not yellow with age.
Since all varnishes contain solvent they are considered as toxic and should be applied in a well-ventilated dust free area. Also, do not apply varnish in temperatures below 60 degrees Fahrenheit and humid conditions (no more than 60% relative humidity).
Retouch Varnish Versus Final Varnish
Retouch Varnish is diluted varnish. When a painting is finished and dry to the touch, a Retouch Vanish is applied to protect the paint film until a Final Varnish can be applied. Often when under painting layers dry, the result is a difference in paint film sheen where on color is dull and another color has more gloss.
Retouch Varnish will remedy this effect resulting in an even sheen.
The Painting Sold Before Final Varnishing
If you sell a painting prior to a Final Varnish being applied, tack a card on the back of the painting with the following information. This painting needs to be varnished on ____ (date), including the brand and the name of the varnish. If possible have the customer contact you for varnishing. You want to control the process, it is your painting.
Final Varnish Application
Since oil paint film oxidation is a slow process, you need to wait to apply a final varnish. It is recommended practice that the Final Varnish be applied to the finish oil painting 3 to 6 months after it is dry to the touch for paintings depending on the thickness of the paint film. For impasto (thick layers of color) or palette knife paintings, varnish after 12 months.
Before you apply the final varnish, you have some additional choices to make in choosing a final varnish.
Choice 1 - Liquid Varnish versus Spray Varnish
Since all varnishes consist of a resin dissolved in a solvent. Liquid Varnishes need to be applied as a thin coat with a soft brush. Allow to varnish to dry completely prior to applying a second coat. Be sure to clean your brush with the appropriate solvent. Spray varnishes as the name implies are in an aerosol can. There is a whole technique for using a spray. It starts with patience. Read the instructions and shake the can thoroughly prior to use. Aerosol sprays have a metal ball inside which you will hear when shaking. Always test the varnish on a scrap of material prior to using it. Spray in light coats. Both are toxic and should be applied in a well-ventilated dues free area. Also, do not apply varnish in temperatures below 60 degrees Fahrenheit or in humid conditions.
Choice 2 - Gloss Varnish versus Matte Varnish
All varnishes are available in matte and gloss and there is even in a satin version. Matte Varnishes contain either bees wax or a silica and need to be mixed thoroughly prior to use. If the varnish has a cloudy substance on the bottom, that’s bee’s wax. This is usually found in a traditional Dammar Matte Varnish. Read the instructions, there is a specific way to prepare the varnish prior to using it. Also, it is not good practice to mix varnishes of different brands since formulations vary.
Varnishing Acrylic Paintings
It is recommended practice to varnish Acrylic paintings. When Acrylic dries it has pores in which dirt, mold, and environmental residue can collect altering the paintings appearance. Before applying a final varnish apply a coat of gloss Acrylic medium and varnish. This will act as a barrier to protect the paint surface if the final varnish needs to be removed for cleaning. Allow to dry for three days and then apply a Final Picture Varnish or Modern Varnish (not Damar).
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