I found this cool pin which shows someone putting crayons into a silicon ice cube tray and cooking them in the oven for a bit. The result is cute, marbled heart shaped crayons. I decided to give it a try.
I have a feeling my tray wasn’t pure silicon as some of it has gone a bit weird. If you do this, make sure you’re using one that can go in the oven! And non toxic crayons… They were difficult to get out, the ones with less crayon in snapped. Make sure you fill the cups!