Q. Do you have any information on speeding up the drying time of oil pastels on canvas? It appears to take up to a year, and shipping is difficult due to the softness and smearing. Also, what can I seal the finished painting with?
A. Unfortunately, it’s almost impossible to add anything to oil pastels to make them dry faster without losing the special character of the medium. Drying time will vary according to the ingredients in the binder and the thickness of the paint films, but essentially the drying process occurs by the oxidation of the oil, and like oil paints they should generally be given between six months and a year to dry.
Some manufacturers sell a blender, or an unpigmented stick of the vehicle that dries a little faster and can be blended in with your colored sticks. But driers can damage oil paint films as the paints age (consider oil pastels to be semisolid oil paints): They can cause cracking of the films and darkening of the colors. For this reason I think it’s best to avoid using driers in any paint, and I recommend against it.
As for varnishing, any surface coating that’s harder than the inherently soft oil pastel will be subject to cracking as the paint continues to move beneath the increasingly rigid coating. But if the brand you’re using is a true oil pastel, with little or no added waxes, then you should be able to apply a light coating of a spray varnish after the painting dries for about a year (or longer for a very thick painting).
To avoid damage to the surfaces of your paintings during shipping, be sure to frame them. Then, as long as the front of the frame projects beyond the picture plane, simply attach a stiff covering of Masonite or heavy corrugated cardboard to protect the delicate surface of the painting. (It’s also a good idea to protect the rear of the painting this way.) This whole package can then be easily crated and shipped.
Mark Gottsegen is an associate professor of art at the University of North Carolina at Greensboro.