Varnishing acrylic paintings

24 Feb 2009

Q: Last week I began to varnish an acrylic painting. When I reached a point where I had added some highlights, the paint just peeled off as the varnish touched it. What could have caused this? Would you recommend spraying varnish on a painting or applying it with a brush?

A: The acrylic paint probably peeled off because the varnish was an oil-based varnish. There are a variety of varnishes on the market—some are designed to accept oil paint and others to accept acrylic paint.

Spray varnish on a painting with caution. The painting should be tilted just high enough—two or three inches—to prevent the liquid varnish from forming puddles, but not high enough for the liquid to run or streak. The spray container should be raised at least 12 inches above the artwork to ensure a soft spray that will fall gently. Be sure to overlap each row as you spray the varnish on the painting. After the first layer of varnish dries, turn your painting and apply a second layer of varnish from the other direction. If you are going to apply varnish with a brush, use a large, soft-bristle brush, and apply the varnish from one end of the canvas to the other, slightly overlapping each row of varnish that is applied.

--by Camille LaPointe-Lyons

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Alan Bateman wrote
on 7 Oct 2009 8:33 PM

I have had a few varnishing disasters. I now avoid the brush-on type of liquid acrylic varnishes, they can lift paint a bit, but that usually only happens if you are heavy handed in your application.

My finishing procedure is as follows, I clean my painting with a damp paper towel and look for spots that are repelling the water, finger prints etc.  I will sometimes mix a very small mount of dish detergent in a spray bottle of water and use that.  A very small amount of the paint may come off on the paper towel so use a light touch. I then let the painting dry.  I place the painting on a flat surface in my work shop, and wear a proper vapor mask.  I like to be able to get all the way around the painting and have a strong light source.  I spray from about 12 inches above the work, keeping my eye low to the board to catch reflecting light and make sure I have covered the whole surface.  You have to find that sweet spot between, just a dusting of varnish, and pools of varnish.  As the spray varnish goes on it looks a little dusty, but in about 30 sec. it usually flattens out to a nice thin finish, so stop every now and then to see if the finish is going to settle out to a nice even gloss.

I also give my spray can a flick towards the floor every now and then to make sure that varnish is not accumulating around the nozzle or my finger tip.  A single free falling drop of varnish can be a huge problem if you are going for that perfect finish.

I should add that I paint with acrylics on board, and like a smooth surface and smooth finished painting.