how long should you let a candle burn
1 You never want any soot or smoke at any time - ever.  Let the candle burn long enough to get the entire top liquid wax. This takes about an hour per inch in diameter of the vessel. So if your candle is 3 wide, let it burn for at least 3 hours. If it doesn't melt all the way to the edge don't panic, but get as close as you can. Sometimes the last 1/4 will burn as the candle goes down.