Why Is My Soy Candle Tunneling? Causes and How to Fix It

Tunneling is when a candle burns straight down the middle, leaving a thick ring of unmelted wax around the edge of the container. It wastes up to a third of the wax, weakens the scent because the melt pool is small, and eventually buries the flame so deep it starves for air. It is the number one complaint about soy candles, and the fix is usually simple once you know which of two causes you are dealing with.

Cause 1: the first burn was too short

Soy wax has a memory. The diameter of the melt pool on the first burn becomes the maximum diameter on every burn that follows. If you lit a new candle for 45 minutes and put it out with a pool the size of a coin, the candle will tunnel from then on, no matter how well it was made. The rule: the first burn lasts until the melted wax reaches the walls of the container, which takes roughly one hour per inch of diameter, so 2-4 hours for most jars.

This is the cause if the candle was bought or made well and the first burn was short. The rest of the burning rules are in how to burn a soy candle.

Cause 2: the wick is too small

If you did burn the first time to a full pool and the candle still tunnels, or the pool simply never reaches the walls after 4 hours, the wick is undersized for the container. The flame is not producing enough heat to melt the wax at the edge. This is a manufacturing problem; you cannot fix it by burning differently, only rescue the individual candle and change the wick in the next batch. Sizing: candle wick size chart.

Other contributing factors

• Too much fragrance oil or dye: both clog the wick and shrink the flame. Stay at or under 10% fragrance.
• Drafts: a flame pushed to one side melts one side of the candle and leaves the other.
• A tall, narrow container: once the flame is a few inches down, it gets less oxygen and burns smaller.
• An untrimmed wick that has bent over: the flame sits against one wall instead of the center.
• Very cold rooms: the wax at the walls loses heat faster than the flame can supply it.

How to fix a candle that is already tunneling

Method 1: the foil trick

Wrap a strip of aluminum foil around the top of the container, folding it inward to form a tent with a 1 inch opening above the wick. Light the candle and burn for 2-3 hours. The foil reflects heat back onto the wax ring and melts it down to the level of the tunnel. Remove the foil and let the candle set. On the next burn it should reach the walls on its own.

Method 2: heat gun

Sweep a heat gun (or a hair dryer on high) over the top of the candle until the ring melts and levels with the tunnel. Let it set fully, trim the wick, and burn to a full pool. Fastest method, and it also resets the wax memory.

Method 3: scoop and level

For a deep tunnel, scrape out the ring of hard wax with a spoon or butter knife until the surface is roughly level with the bottom of the tunnel. Save the wax for a wax warmer. Trim the wick and burn to a full pool. Less elegant, but it works when the tunnel is already several inches deep.

How to prevent tunneling

1. Size the wick with a burn test, not just the chart, and go one size up when using 8-10% fragrance.
2. Burn the first time until the pool reaches the walls.
3. Burn 2-4 hours per session afterward, never 30-minute sessions.
4. Trim the wick to 1/4 inch before every burn.
5. Keep the candle out of drafts and away from air vents.
6. Prefer wide, short containers over tall narrow ones, and two wicks for anything over 3.5 inches across.

Every other soy candle problem, with fixes, is in our soy candle troubleshooting guide.