I might put a fridge box above a box of crayolas. But, I did love melting crayons on our cast iron radiators. That was cool.
I’ll bet the salmon melted especially pretty.
I used to melt them on the radiators at school - the radiators had metal covers with lots of horizontal vent openings on top that were just wide enough to support a crayon (with the paper wrapper removed, of course) lengthwise - until the moment when the crayon was melted enough to fall through the vent cover onto the radiator and then splat on the floor...