
There is not tutorial for making crayon rings, but
Timothy Lilies has created a fun fashion accessory using (and I'm guessing here) classic resin casting techniques.
I would imagine that melted crayons would mold nicely in a cast made for resin. Having done some resin casting for miniature buildings, I can tell you that it's not all that hard. Check out Micro Mark for
supplies and a
basic tutorial on making a rubber mold. The process from there is pretty simple. You'll need a ring to use as a template. See how Mr. Lilies has chosen a very streamlined shape? That's the kind of thing you want to look for. Stay away from rings with lots of detail and thin sections. You could try sculpting a ring template from wax or soap if you are really industrious.
Once you have your template, it's an easy thing to make your mold. I think for these rings I'd make a two part mold that splits in the middle. The directions on the Micro Mark website (or that come with your kit, should you get a full resin casting kit, will tell you how to do this. When the mold is set up, spray it with mold release and instead of using resin, use melted crayon. You'll need to clean up any casting lines or sprue, but wax trims nicely with a craft knife.
Voila! Do a set in all the colors of the rainbow!
Photo used without permission from Future Perfect.