Use glass wine bottles with inner bottom cut out for smaller version of the same design. When you evaporate and condense water it becomes pure and is completely safe to drink. Nasty chemicals and bugs do not evaporate with the water.
DIY HOME Candle Powered Heater - I've been looking a various ways to make these and this guy has by far the best setup. It isn't so much a how-to video. He is just showing what he used to construct his version of the terra cotta pot candle heater.