Your candle will burn clean and evenly down to the bottom of the glass if you are careful to take the following steps:
After blowing out the flame, if necessary center the wick in the liquid wax. It is essential to cut the wick short before relighting the candle to avoid unnecessary smoke. Do not place the candle in a wind draft or directly on a glass or marble surface. Never leave a burning candle unattended. Never move or tip a burning candle. Keep out of reach of children.