I bought silicone moulds to recycle crayons. I’ve been learning a lot, mostly that they need to be all the way full or the resulting crayons will break too easily—often while being unmoulded. This is an easy craft project, though, and kid-friendly, since artistically arranging the crayon bits is safe for anyone old enough not to eat them. They take about 15 minutes to melt in the oven at 250F (200 melted many but not all brands of crayons).
I’m not going to be able to reuse these moulds for food, which is too bad—not all the pigment comes off cleanly.
I’ll have to get separate ones for chocolates, and keep these for crafts. I bet they’d work great for clay or soap.