Q. I mistakenly applied glossy damar varnish to an oil painting that had been drying for several months, but I wouldve preferred a matte finish. Is there a way for me to still give the piece a matte look?
A. Damar varnish, made from the resin of coniferous Asian trees, is applied to oil paintings to protect them from dust and other airborne contaminants. Your varnish problem is complicated and contains risk factors.
Since your painting currently has a glossy surface, subsequent varnish applications may bead up like water on a newly waxed automobile. If you choose to remove the glossy damar, you run the risk of dissolving the paint along with the varnish. This is especially true if you used damar as part of a painting medium. In that case, leave the glossy varnish alone and apply a layer of matte damar over it.
Apply a matte finish on top of the glossy one using either a brush-on application or a spray varnish. If youre comfortable with your spraying skills and have a good can of varnish that sprays the contents evenly, apply the varnish in quick, even passes. Check to see that the varnish is not beading up. If it is, the varnish is reacting to the glossy surface and not spreading properly.
If youre proficient at varnishing with a brush, you may want to apply a matte damar coating to the surface that way. Bear in mind that solvents in the matte varnish may dissolve the existing varnish, so apply the new coat lightly. To obtain the best results, heat the varnish first to fully integrate the wax that serves as a matting agent.
If, on the other hand, you choose to remove or thin the glossy varnish, I advise caution. Working in a well-ventilated space, test the solubility of both the varnish and the paint layer beneath by applying a small amount of mild solvent (such as mineral spirits) on a cotton swab, then rubbing the painting and checking to see if either the varnish or paint is coming off.
Continue to carefully rub away the varnish before applying the matte coating. Trained conservators with years of experience approach this task with a healthy dose of respect, and so should you.