Verified answer

Use a pan inside of a pan (double boiler) -use some that you're not crazy about--strain the old candles with a coffee filter as you're pouring the wax into the molds. anything paper , like towel tubes, won't make good molds,the wax will seep through and make a MESS. Something with a solid bottom , like a cup, is a better bet. Crayons have a higher melting point than regular candle wax, so they're not god to use. except as for flakes of color in plain candles. But if you add crayon flakes, they will sink to the bottom. (experience) also, don't put stuff into the candles, like potpurri, because, even though it's kinda funny when the whole thing catches fire, it's not safe.(experience there too) a glass meat/candy thermometer is good for making sure your wax doesn't get too hot and catch fire or melt the mold. An acrylic glass with a hole drilled in the bottom for a wick works good as a mold. Just make sure the mouth of the glass is wider than the base so the candle can slide out easy.

Old egg cartons make nifty little candles. They burn for about 4 hours if you use good wax. Any type of cardboard tube, e.g. old toilet roll centre roll. Old crayons will smoke something terrible.

Please do not melt old candles down, a friend of mine did that for years and one time something went really wrong and the wax exploded on his face, so pls don't try that.