Why your candle tunnels, and how to stop it

You light a candle. It burns down the middle in a neat little cylinder, leaving a thick ring of wax stuck to the sides. Within a few burns, the flame is drowning in a wax well and the outer inch and a half hasn't been touched. That candle is now a wasted forty quid.

This is called tunnelling, and it's the single most common way that a good candle gets ruined by an accidental mistake in the first hour of its life. Here's what's actually happening, why it happens, and how to make sure it doesn't happen to yours.

The first burn matters more than any other.

The rule that most people miss: a candle has a memory. The first time you light it, the wax pool that forms sets the pattern for every burn afterwards. If the wax only melts an inch across, that's the width your candle will burn at for the rest of its life. It will not correct itself later. Every subsequent burn will melt the same inch, dig deeper, and leave the rest untouched.

The fix is simple: on the first burn, leave the candle lit long enough for the wax to melt all the way to the edges of the vessel. In a properly wicked candle, that takes between two and three hours depending on size. You want a full, even pool of liquid wax stretching from edge to edge before you blow it out. If you snuff the candle after twenty minutes because dinner's over, you've locked in a tunnel.

Why cheap candles tunnel and better ones don't.

Tunnelling isn't purely user error. A candle can be set up to fail from the moment it's poured.

The main culprit is an undersized wick. Mass-produced candles often use the smallest wick the maker can get away with. A smaller wick uses less material, burns slower on the shelf test, and produces a longer stated burn time on the label. It also can't melt a full pool of wax across a wide vessel, which means the candle tunnels no matter what the customer does.

Wick sizing is one of the least glamorous and most important parts of making a candle properly. The wick has to match the diameter of the vessel, the type of wax, the fragrance load, and the room temperature the candle is likely to burn in. Get it wrong by even one size and the candle either tunnels or smokes. Every candle we pour is wick-tested before the batch is sold, which is why nothing leaves our workshop until we've watched it burn.

What to do if your candle is already tunnelling.

The fix depends on how bad it is.

If the tunnel is shallow (less than half a centimetre of unmelted wax around the edge), light the candle and leave it going for three or four hours in a still room. The heat will slowly melt the outer ring and start to reset the pool.

If the tunnel is deeper, you can try the foil trick. Wrap a piece of aluminium foil around the top of the candle, leaving the flame exposed but reflecting heat back onto the unmelted wax. Burn for two hours. This forces the outer wax to melt. It's ugly but it works.

If the tunnel is severe (the flame is drowning and the wax pool is more than a centimetre deep), the candle is probably beyond saving. You can carefully melt the top layer of wax with a hairdryer to level it, then relight and burn properly. But at that point you've lost most of the fragrance oil that was suspended in the top layer, and the candle will never smell as strong as it should.

Three rules for every candle you ever burn.

One, first burn to a full melt pool. Every time, no exceptions. Set aside two to three hours before you light a candle for the first time.

Two, trim the wick to five millimetres before every burn. A long wick produces a big flame, which burns the wax hotter and faster, which shortens the life of the candle and can produce soot. Wick trimmers are three pounds on Amazon and change how every candle you own performs.

Three, don't burn a candle for less than one hour or more than four hours at a stretch. Under an hour, you'll tunnel. Over four, the wax overheats, the flame gets aggressive, the vessel gets hot enough to be a hazard, and the candle burns through faster than it should.

Follow these three rules with any well-made candle and you'll get the burn time on the label. Ignore them, and even the best candle in the world will disappoint you.