Varnishing is an aesthetic decision. Robert Gamblin recommends paintings be varnished unless artists truly dislike the look. While waiting 3 - 6 months is best, painters using Gamvar can safely varnish sooner because Gamvar's mild solvent will not dissolve the glaze layers of paintings and paintings today dry quicker. Gamblin Artists' Grade Oil Colors dry more quickly than oil paints of past centuries. (Then linseed oil was usually contaminated with weed seeds that slowed down the drying time of paintings. Contemporary refined linseed oil is pure linseed oil.) Painters can also leave a note on the stretcher bars "ok to varnish in future."
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Gamvar is formulated for both the present and future.
Robert Gamblin formulated GAMVAR, a low molecular weight (LMW) synthetic resin varnish, based on research at the National Gallery of Art. Gamvar has a refractive index similar to damar natural resin varnish. GAMVAR is better because it does not yellow and remains easy to remove with mild solvents such as Gamsol OMS. Adding it as the top layer will saturate the colors of paintings and intensify the transparency of glazes.
From painters' point of view, Gamvar is an excellent varnish because your paintings will look beautiful today. From conservators' point of view, Gamvar is an excellent varnish because they will be able to clean your painting in 100 years without using such strong solvent that they may harm the paint layers underneath.
Gamvar may be used as a retouch varnish (1 part Gamvar to 5 parts OMS).
Like damar, Gamvar has a high shine. To make Gamvar less shiny, dilute with up to 50% OMS. Also, painters can make a matting agent from 2 fl oz of Gamsol OMS and 1 teaspoon of Cold Wax Medium. Dissolve the wax completely in Gamsol. Add this in place of a percentage of OMS to make Gamvar more matte.
If you prefer a matte varnish, Robert Gamblin recommends you varnish with cold wax medium.
Gamblin Cold Wax Medium can also be used as a traditional matte varnish. Apply a thin layer of Cold Wax Medium on to the painting. With a circular motion, apply the Cold Wax paste with a lint free cloth. Cold Wax Medium can be applied as a varnish as soon as the painting is dry enough not to be disturbed by the act of applying the wax paste. For large paintings on flexible supports, consider backing the painting before applying Cold Wax Varnish. Wait approximately 24 hours and then buff the painting to the desired sheen. The Gamblin Cold Wax Varnish is easily removed with odorless mineral spirits.