What cause black smoke from Candles?
Usually when the the candle is burning near the wall you might notice that even the wall turns blackish, that is soot.However, some amount is natural, heavy amounts of black smoke and soot are a concern and can be prevented.
Small amounts of smoke and soot are natural parts of the burning process. In a candle, the wax is the fuel and the wick is the fuel-delivery system. With well-made and properly maintained candles, the soot and smoke will be minimal, and will not leave black residue behind. Excess smoke and soot are evidence of an incomplete chemical reaction that could be caused by a variety of factors, some of which can be easily remedied.
The primary cause of black smoke is an overly long wick. When a candle burns, the wax near the flame melts and the liquid wax is pulled up the wick to feed the flame. If the wick is too long, the balance of heat and fuel will be off. This throws off the chemical reaction and can produce excess soot and smoke. Trimming wicks to between 1/8 inch and 1/4 inch before you light the candle is the easiest way to prevent black smoke.
Another common cause of black smoke is a drafty environment. Candle flames flicker; it’s part of their appeal. But if the flame is blowing in the wind or flickering excessively from a draft, smoke and soot may result. If you see your candle flames wavering excessively or blowing around, check for drafts. Turn off the ceiling fan. Close the window. Move the candle to a more protected spot. Keeping your candle flames away from too much moving air will help them burn more cleanly.