The first time you light your candle, we'd advise you keep it lit for around 2 hours, or until the wax has melted to the edge of the jar (full melt pool).This will prevent any subsequent tunneling. Tunnelling means that the wick is burning straight down the centre of the candle without creating a full melt pool within 2 - 4 hours of being lit. Ideally you'd trim the candle's wick to around 3mm before you light it. We'd also recommend burning your candle for 1-2 hours at a time. Don't let it burn all the way to the bottom, and protect the surface under the candle.