You’re Lighting Candles Wrong
You are probably familiar with the annoying ring of unmelted wax that sometimes appears on large candles. This is called “tunneling” and it’s not just ugly – it shortens the life of the plug and makes it difficult to actually use it.
Candle tunneling occurs when the flame absorbs the wax only towards the center, leaving the edges intact and completely solid. Over time, this causes the wick to sink down the middle, surrounding it with a “tunnel” of unmelted wax. This is bad for two reasons: firstly, any unmelted wax is waste, which means that a candle in a tunnel will not last as long as a properly burned one. (The prettier and more expensive your candle, the more annoying it is.) Second, tunneling makes it harder for your candle to light and more likely to go out due to falling drops of melted wax, which is annoying.
How to light candles correctly so that they do not rot
Tunneling occurs due to uneven burning, usually from extinguishing a new plug too soon. The easiest way to prevent this is to always let new candles burn until the surface is completely melted, which can take up to several hours depending on the size of your candle. Other common causes of tunneling are uneven surfaces, drafts, and a wick that is off-center or too short. The first two are easy enough to deal with—always light your candles on flat surfaces, away from open windows and fans—and wick problems are a little more difficult. As long as you avoid trimming the wick before the first burn, it should stay long enough to be usable, but there is no quick fix for an off-center wick. If you don’t want to melt and move the wick yourself, you’ll have to live with a certain amount of uneven burning.
How to fix candle tunnels
The good news is that tunneled candles can be salvaged. The quickest and easiest way to do this is to use the foil method : cover the candle with foil, then cut or tear a hole in the center to give the fire a rest, making sure the foil covers the tunnelled wax around the edges. Light the candle and let it burn until the surface becomes liquid. You can also use an oven to line the tunnel candle: The Kitchn recommends preheating the oven to 175ºF and heating the candle on the baking sheet for about five minutes, or enough to melt the wax.
Whatever technique you use to rescue the candle from the tunnel, be sure to finish the job by freeing the wick of any melted wax that coats it. While the wax is still soft, use a toothpick to remove the wick and remove any excess that could extinguish the flame when it melts.