Sounds contradictory doesn’t it? Intuitively, it seems that burning a candle for a longer period of time would make the candle burn away faster. However, allowing a candle to burn all the way across its surface before extinguishing the flame prolongs the candle’s life. This applies to candles in jars and other containers (not pillars–they are designed to burn differently).
This simple act of letting your jar candle burn longer helps to prevent tunneling. Tunneling occurs when the candle melts down the middle leaving a “wall” of unmelted soy all the way around the candle container. The next time you light the candle, that initial “wall” of solid soy will act as a barrier; your candle won’t be able to melt all the way across the container and much of your candle will be wasted.
If your candle begins to tunnel, use a hairdryer to melt the soy until the soy oil is melted all the way across the container. Then trim your wick to 1/4-inch. Your candle will be renewed and ready for lighting once again.