Why Your Candle Tunnels (and How to Fix It)

You made a candle and it burned straight down the middle leaving a wall of wax, that is tunnelling, and it is the most common beginner problem. It comes down to wick size and the first burn. Here is how to fix it.

HobbyStack EditorialMay 25, 2026Updated July 13, 20261 min read

Part of the Candle Making hobby guideSee the full overview: what it involves, what it costs, and how to start.

Key takeaways

Tunnelling (the flame burning a narrow hole down the centre, leaving unmelted wax around the edge) is almost always a wick that is too small for the container.
The wick has to be sized to the diameter of your container. Too small and it tunnels; too large and it smokes, soots, and burns hot.
The first burn matters most: always burn a new candle long enough for the melt pool to reach the edges (often 1 to 2 hours per inch of diameter).
Getting the wick right takes testing. Make test candles, burn them, and go up or down a wick size based on the melt pool.
A full, even "melt pool" all the way to the glass on each burn is the goal. It means no tunnelling and no wasted wax.

What tunnelling is and why it happens

Tunnelling is when a candle burns a narrow shaft straight down the middle, leaving a thick ring of unmelted wax clinging to the sides of the container. It wastes a lot of wax and eventually drowns the wick. The main cause is a wick that is too small for the width of the container: a small wick produces a small flame, which can only melt a small pool of wax, so instead of the melt spreading out to the edges it just burrows downward. The fix is a wick sized correctly to your container’s diameter, one big enough to melt the wax all the way out to the glass. So if your candles tunnel, the first thing to change is almost always the wick, going up a size.

Wick size is the whole game

Getting the wick right is the central skill of candle making, and it depends on the container width, the wax type, and any fragrance. Too small a wick tunnels and leaves wax on the walls; too large a wick burns too hot, produces a big flickering flame, gives off soot and smoke, and can make the glass dangerously hot. Wick manufacturers publish sizing charts that suggest a wick series and size for a given container diameter and wax, and that is your starting point, but it is only a starting point. Because the exact right wick depends on your specific wax, fragrance load, and vessel, you have to test: pour a few candles with different wick sizes, burn them, and see which gives a clean, full melt pool without a huge sooty flame. Candle making is often described as "wick testing," because that really is most of the craft.

The first burn, and reading the melt pool

Even a correctly wicked candle can be made to tunnel by a bad first burn. Wax has a "memory": the candle tends to re-melt only as far out as it went on its very first burn. So the rule is to let a new candle burn long enough, on that first lighting, for the melt pool to reach the edges of the container, which typically takes something like one to two hours per inch of the candle’s diameter. Snuff it out too soon on the first burn and it will tunnel from then on, no matter how good the wick. Each time you burn, look at the melt pool: it should reach the glass all the way around (a "full melt pool"). If it consistently does, your wick and burning habits are right. If it leaves a wall of wax, go up a wick size or check that you are giving it a long enough burn. The full, even melt pool is the target that means you have solved tunnelling.

Trim the wick to about 5 to 6 mm (a quarter inch) before every burn. A wick left too long gives a big, flickering, sooty flame, mushrooms carbon on the tip, and can undo an otherwise well-made candle. Trimming before each light is a tiny habit that noticeably improves how cleanly and evenly a candle burns.

Common questions

Why does my homemade candle tunnel?

Almost always because the wick is too small for the container. A small wick makes a small flame that can only melt a narrow pool of wax, so it burrows straight down instead of melting out to the edges, leaving a ring of wasted wax. The fix is to use a larger wick sized to your container’s diameter. A bad first burn (snuffing it before the melt pool reaches the edge) also causes tunnelling because wax "remembers" its first burn.

How do I choose the right candle wick size?

Start from the wick manufacturer’s sizing chart, which recommends a wick series and size for a given container diameter and wax type. Then test, because the exact right wick also depends on your specific wax, fragrance load, and vessel. Pour candles with a couple of wick sizes, burn them, and pick the one that melts all the way to the glass without a huge, sooty, flickering flame. Too small tunnels; too large soots and overheats. Testing is how you dial it in.

What is a full melt pool and why does it matter?

A full melt pool is when the top layer of a burning candle has melted all the way out to the edges of the container, with no ring of solid wax left on the walls. It matters because it means the candle is burning efficiently, not tunnelling, and not wasting wax. Achieving a full melt pool, especially on the first burn, is the sign your wick is correctly sized and you are burning the candle long enough each time.

How long should I burn a candle the first time?

Long enough for the melt pool to reach the edges of the container, which is usually around one to two hours per inch of the candle’s diameter. This first burn is critical because wax has a "memory" and tends to only re-melt as far as it did the first time. If you snuff a new candle before the melt pool reaches the glass, it will likely tunnel on every future burn, even with a good wick. Give the first burn the time it needs.

My candle smokes and has a big flame, what is wrong?

That is usually the opposite of tunnelling: a wick that is too large for the container. An oversized wick produces a big, flickering flame with soot and smoke, can make the glass dangerously hot, and burns through the candle too fast. Go down a wick size, and always trim the wick to about a quarter inch before each burn. As with tunnelling, the solution is dialling in the correct wick through testing, then maintaining it by trimming.

Bottom line

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