If the candle wick is too long or sometimes the air current disturbs the candle flame, it creates a teardrop shape and some small amounts of unburned carbon particles that is soot, will then escape from the flame as a visible wisp of smoke. Every candle will smoke or soot as long as the candle flame is disturbed. However, a well made candle with a proper wick length will produce no soot when burning properly.
Ways to avoid smoke from a candle
Make sure the candle wick is not too long if so then trim it before burn the candle, always avoid placing the candle on vants or air currents. Pay attention to your candle if it smokes or flicks , then its not burning nicely so it shoud be exinguished. let the candle to cool for a minute or so then trim the wick and make sure the environment is draft free.Then you can light your candle again