Don,t you just hate having to put glass over pastels, the cutting of glass, the cleaning and not to mention the weight. Here are a few small pastels that I experimented with using wax melted with a heat gun. As we know any liquid will alter the colors so it is best to use very vibrant colors when doing this.This way the colors will not darken down so much.
I purchased some wax beads, painted a few small pieces and gave it a shot. As I said, I have a heat gun, inexpensive ( with a Hobby Lobby or Michael's coupon ), I sprinkled the wax beads on top and held the heat gun at a distance till the wax started to melt. The blower of the heat gun will move the melted wax around. It created an interesting look. I don't think this will work on a large painting but if you have a painting that is not a keeper then give it a try. It was fun to play.
The first one is the most successful.