Why does my candle tunnel? (and how to fix it)

If your candle burns straight down the middle and leaves a ring of hard wax stuck to the sides of the jar, that is tunnelling. The short version: it almost always comes from a first burn that was too short. Candles have a memory, and if you blow one out before the melted wax reaches the edge, the candle keeps to that smaller pool every time after.

The good news is that tunnelling is both fixable and easy to prevent once you know what causes it. Here is how it happens, how to rescue a candle that has already started, and how to stop it happening again.

What is candle tunnelling?

Tunnelling is when a candle burns a narrow well straight down the centre and leaves unmelted wax clinging to the sides. The flame sinks lower and lower into that tunnel, the scent fades, and eventually the wick drowns in its own melted wax. You have paid for a full candle and only about half of it ever gets used.

Why do candles tunnel?

Candles tunnel when the wax does not melt all the way to the edge. The most common reason is a first burn that was cut short, but the wick, the room, and your burning habits all play a part.

• The first burn was too short. Wax has a memory. If the first burn does not melt the whole top surface, the candle remembers that smaller pool and tunnels from then on. This is the single biggest cause.
• The wick is too small for the jar. An undersized wick cannot throw enough heat to melt the full width of the wax.
• Draughts. A fan, an open window, or air conditioning pulls the flame to one side, so it burns unevenly.
• Short, frequent burns. Lighting a candle for twenty minutes at a time never gives it the chance to catch up.

How do you fix a candle that is already tunnelling?

You can usually rescue a tunnelling candle. Two methods work well, and both aim to melt the top layer of wax back to a flat, even surface.

• The foil method. Trim the wick, light the candle, then wrap a loose collar of aluminium foil around the top of the jar, leaving a hole in the centre for airflow. The trapped heat melts the wax on the sides. Leave it for an hour or two until the surface is level, then remove the foil.
• The hair dryer method. Warm the top of the candle with a hair dryer until the surface wax melts and levels out. Let it re-set flat before the next burn. This is quicker but only smooths the very top layer.

For a deep tunnel it may take a couple of goes, but most candles come back beautifully.

How do you stop a candle tunnelling in the first place?

Let the first burn go long enough for the melt pool to reach the edge of the jar, which is usually two to four hours. That one habit prevents most tunnelling. After that, a few small things keep the burn even.

• Give every new candle a full first burn, until the entire top is liquid edge to edge.
• Trim the wick to about five millimetres before each burn for a steady, even flame.
• Burn for three to four hours at a time, then let it cool and re-set.
• Keep it away from draughts, fans, and open windows.
• Burn on a flat, level surface so the wax pools evenly.

Does soy wax tunnel more than paraffin?

No, if anything soy is a little more forgiving. Soy wax has a lower melting point than paraffin, so it melts across the surface more readily, but it still needs that full first burn to set an even memory. Our Aurora soy candles are made with the wick sized to the jar to help the melt pool spread, though the first burn rule always matters most.

The habit, not the candle

Tunnelling is less a fault in the candle and more a habit in how it is burned. Give it a proper first burn, keep the wick trimmed, and you will get every last hour of scent you paid for. For the full routine, our guide to candle care and safety covers burn times, wick trimming, and storage in one place, and there are more quick wins in our five ways to stop damaging your candles.

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