I read this awesome book titled Skinny Bitch by Rory Freedman and Kim Barnouin where the authors discussed why it matters what kind of candle you use. The authors recommend to use soy candles because traditional candles are made from paraffin wax which is waste from petroleum production. Soy wax was only invented 17 years ago and is American grown, biodegradable and cleans up with plain old soap and water.  The black smoke/soot you see coming out of regular candles pollutes the air and your health. But even with soy candles you have to find out what kind of wick they use and that it's not made from lead, but rather cotton and fragranced with essential oils. I really like Archipelago's soy candles available at Whole Foods.  100% soy candles can't hold their shape so they will be in jars, but you can find candles that are a mix of soy and palm oil that are free standing pillars. Soy wax has a lower melting point than paraffin wax and because of this soy candles will burn longer than paraffin candles. You'll see the difference when you burn them as there will be no black soot coming out and you can feel good that it didn't emit any toxins into your air.