We sorted the wax on color, chopped it up and melted it 'au bain marie'. When it was completely liquid, we poured it into the mould.
We had two moulds: a cylinder and a square one. We put 'em in pans of cold water, to speed up the cooling process. Wax keeps warm quite long!
The end result. You can see the layers quite nicely, which I like. They're a bit wobbly: we have to trim the undersides so they'll stand up straight again. And the cylinder candle has a huge dent in it, where it cooled unevenly (or something)...
Still, I'm quite pleased with the result. It's not very economical (the moulds are pricey, candles are not), but it makes something useful from something that otherwise would be trash.