Bill Martin's Guide to Oil Painting
Varnish Restores Luster and Protects Your Painting
There are two types of varnish used in oil painting. They are Damar Varnish and a thinner version of Damar Varnish called Retouch Varnish.
Retouch Varnish is used during the course of the painting. Damar Varnish is used at the end of the painting.
Bring Up Your Colors Using Retouch Varnish
To TEMPORARILY restore colors and unify the painting's surface, the thinner version of DAMAR varnish, called RETOUCH VARNISH, is applied. The thin retouch varnish layer allows the paint to continue its deep drying thus avoiding cracking.
Retouch varnish can be painted over and retouch varnished again many times. Because retouch varnish restores a color's original luster it helps in matching dried colors.
When Your Painting is Finished Put on a Final Varnish
All oil paintings should be varnished. Oil paints dry to various degrees of gloss or matte, which can slightly alter the original color. The Final Varnish is used to permanently restore the original luster of the colors and unify the surface with a single finish. It also acts as the painting's protective layer.
An oil painting should be dry for three to six months, depending on the thickness of the paint, before its FINAL varnish is applied. DAMAR VARNISH is the best for oil paintings.
Two coats are used for the final varnish. Allow each layer of varnish to dry overnight. Apply the varnish with a soft brush on a horizontal painting (see Brushes). Use even strokes in a single direction for each layer.
(NOTE To paint over a final varnish is an example of painting thin paint over thick paint and it will surely crack. Sign your name before you put the Final varnish on your painting.)
Brushing or Spraying the Varnish
RETOUCH VARNISH is effective as a spray because there is less of a chance of smearing any semi-dry paint. If a color is not completely dry the turpentine in the retouch varnish can loosen the paint if applied with a brush.
FINAL VARNISH is best applied with a brush because it provides a more even protection for the painting. The painting ready for its final varnish of course will always be thoroughly dry.
Use Good Ventilation
If you brush on or spray on the varnish, good ventilation is essential until the varnish is thoroughly dry. Don't breathe the vapors.
Make Your Own Damar Varnish and Retouch Varnish
Most commercial Damar and Retouch varnishes are adequate but if you want your own, this is how. For a final Damar varnish mix one part DAMAR RESIN with ten parts TURPENTINE by volume. Let the resin dissolve overnight or longer depending on the sizes of the chunks of Damar resin. For Retouch Varnish fifteen parts turpentine to one part Damar resin works well. Both mixtures will need to be filtered through cloth to remove traces of bark, twigs and leaves.