Sorry if you know this, but: Oil pastels are made with a non-drying oil, not with the drying oils used to make oil paint. Your 'pastels' are actually oil sticks, they will either dry hard, or will develop a thin film that needs to be repeatedly scraped off in order to use. To make true oil pastels, you'll need a different oil -- originally coconut oil was used, but nowadays they're made with mineral oil. You could technically use a variety of vegetable oils, but you have to watch they don't go rancid or cause damage to the paper. The only other ones I'd try, personally, would be castor oil or jojoba oil.
yes, thank you, exactly! I figured that out awhile after I made them (and they developed a skin, like oil sticks). I also made several that had too much wax in them, so they were more like crayons. I still need to try this again, to make a better oil stick, and also thought I’d try using mineral oil for the oil pastel? I believe that it is non drying.
Interesting, so that wasnt just an odd feature of Activated Charcoal. Notably I used the same emulsion on other pigments using Olive Oil and didnt get the film.
