Of the many the posts I have published , few have received as many comments as Gamvar: Gamblin’s Easy-to-Use Picture Varnish for Oil Painters. Varnishing is quite problematic for many artists, and that post offered some straightforward advice.
One of the issues the original post did not address was the problem of streaking — those telltale brush marks left after the varnish has dried. I’ll discuss this here, but I’ve also added it as an addendum to the original post.
Before I describe the technique for dealing with steaks, I should mention that if you are getting streaks you are are almost certainly applying too much varnish. As I wrote in the original post, “Always apply varnish as thinly as possible, avoiding visible brush strokes. Those new to varnishing overestimate the amount of varnish necessary and apply far too much. Imagine that you are trying spread the varnish as far as it can go.”
When a painting’s surface is more textured, say, from the weave of the canvas or the texture of the strokes themselves, streaking will be less noticeable. However, the potential for streaks is greater when the surface is very smooth to begin with, and the paint is applied very thinly with little or no visible texture. Then there is no texture to interrupt or camouflage or the streaks.
Immediately after applying a very thin layer of varnish, use a very soft, delicate, “fluffy” brush and lightly dab the surface. This breaks up the streaks. Use a quick, light up and down dabbing motion, and pay close attention that you don’t miss any spots. The brush shown here is a 2-1/2 inch wide Asian-style Hake wash brush with sheep hair. Note: It is preferable to not use the same brush for this dabbing step as you did for the varnishing. The varnishing brush is laden with wet varnish; it’s hairs will be clumped together and have less “fluffiness.” Use a dry brush with hairs that are still fluffy and open. If you must use the same brush as you used for varnishing, wipe it back and forth on a roll of paper towels until most of the remaining varnish has been soaked up. The hairs should regain some of their fluffiness.