Badk in my working days, and before those fancy paint-upsidedown cans of spray paint, we used to carry lumber crayons in our bags to mark things on the pavement. We discovered that one crayon would melt into a blob, but if you took three or four and rubber banded them together they would not melt. Go figure. I don't know if this would work with candles or not, might just make a bigger mess, but it might be worth a try...