Varnishing is an aesthetic decision but also practical. Robert Gamblin recommends paintings be varnished unless artists truly dislike the look. While waiting 3 to 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.
Water clear, Gamvar is a revolutionary development in protecting paintings from dirt and dust. Gamvar picture varnish is a low molecular weight synthetic-resin gloss varnish developed by conservation scientists at the National Gallery. Package makes enough varnish for 8x10 square feet of paintings made with oils as well as acrylics. Gamvar can also be used for retouch.

With a high refractive index similar to that of natural resins, colors are fully saturated to bring out the best in the painting. Unlike varnishes made from natural resins like dammar and mastic, Gamvar does not yellow with age or become more difficult to remove. It contains a UV stabilizer and offers some measure of protection to less lightfast pigments, depending on how thickly it is applied.
Caution: Follow safety instructions carefully. Not suitable for use by children.