If you're a fan of candles, you've probably wondered if wax melts cause soot. The simple answer is no—wax burners don't cause soot. The key to preventing soot formation is to ensure that the candle flame is hot enough to vaporize the liquid wax. Keep the wick trimmed to ¼ inch and the flame high enough to vaporize the liquid wax. If you notice soot buildup on your candles, extinguish the flame and let the wax cool before wiping it away.