Q. Can I protect my oil pastels from dust with a spray or brush varnish and, if so, do they still require being covered under glass? Are there some other options for framing oil pastels?
A. Yes, I think oil pastels—which are oil paints with a wax additive, in stick form&$151;can be varnished once theyre dry. Depending on how thick the layers of paint are, you might have to wait a year from the date you finish the painting for the work to dry. Also be aware that these products contain a wax, and could therefore be dissolved by the solvent in a varnish. If its completely dry when varnished, it could be fine until sometime in the future when a conservator tries to clean the painting—then, the cleaning solvent could dissolve the paint. But as a conservation scientist I know once said, varnishing shouldnt really be thought of as protection; varnishing is an aesthetic choice. True, correctly formulated and applied varnishes can be somewhat protective of whats underneath, but varnishes—especially if they arent properly applied in very thin layers—can often cause their own forms of trouble: yellowing, cracking, crazing, blooming, etc. If you want true protection, framing behind glass or acrylic glazing is best. If this oil pastel painting is on paper, I recommend that. If its on a stretched fabric support, simple framing ought to do the job—and youll have to decide for yourself whether to varnish it.
Mark Gottsegen is an associate professor of art at the University of North Carolina at Greensboro and chair of ASTM Internationals subcommittee on artists materials.