Hmm. Waxy stuff melts, doesn't it?
Here's what happens when you put pastel crayons in the oven.
First up, I tired drawing on a piece of scrap board, conveniently broken into size by my sister via Taekwondo practice. The pastels didn't take kindly to the surface at first, so I softened them up a bit by holding them over a lit candle for a few seconds at a time. They got all smeary. I put the colorful, smeary piece of wood in the oven at 225 for about 20 minutes.
Next up, melting the pastels and dripping directly on the board. If rubbing warm pastels on the surface of wood made them stick half-heartedly, surely dripping hot melted pastel from a few inches above would give greater adhesion. Less control, of course, but that wasn't really my interest any more -- I just wanted to make pretty colors. After dripping (and it wasn't quite as drippy as I expected), I put the board into the oven again, this time at 275 for 15 minutes.
Flammability was not an issue. :D
The colored patches meshed together a little better, and even traveled across the board... while in other places they didn't blend at all, just met and evened out. Also, I had a lot of little bubbles pop up from the wax. They left a sort of mottled surface texture.
Once more at 320 for 30 minutes:
...and that's enough of that.
Lastly, I wanted to try making a wacky crayon. You can recycle broken wax crayons into a shiny new chunk-o-crayon that looks exciting to little kids (and anyone easily distracted by bright colors, like me). It seemed like waxy pastel crayons might benefit form the same treatment. I got a piece of tough old tupperware, broke bits off the pastels, and jumbled them up in the tupperware mold. A metal mold (like a muffin tin) would be the safer choice, but I didn't have one of an acceptable size. The piece-filled mold was placed on a scrappy baking sheet for the sake of stability and catching any melt that might bubble over. This ended up not being an issue at all, as the pastels melted and sank to the bottom of the mold without any spitting and very minimal bubbling.
Bake for 30 minutes at 300, and voila:
...not at all worth eating, but visually intriguing, nonetheless.
EDIT: And, at Keira's insistence, here is how it draws:
The pastels did in fact melt just like normal crayons do, and the tupperware was not affected except for some colorful residue that I scrubbed out later. I should mention that there was a layer of translucent, cloudy oil/wax that formed on the surface of the block as it was forming in the oven. When cooled, this layer was the same consistency as that of the colorful block below it, but rubbing it on paper produced no color. I shaved the layer off with a craft knife before taking the image you see above.
In conclusion, one can indeed put cheap pastel crayons in the oven to produce various effects without fear of immolation, explosions, bizarre and persistent smells, or ruining the oven with little waxy splatters. The actual quality of the effects achieved remains debatable... but experimentation is always preferable to throwing away unused art supplies.
...and I still have a lot of pastel crayons to use up. -_-;
*In truth, there is no such thing as kiddy grade or student grade materials; you can make real, sincere art out of anything -- the only limit is the artist's vision. :D