Why your candle tunnels, and how to stop it
Soy wax has a memory. It forms in the first two hours, and it does not revise.
· The Bath Aura
Melt pool at the glass edge, overhead, lit
Tunnelling is when a candle burns a narrow shaft down its middle and leaves a wall of unburnt wax clinging to the glass. You paid for that wall. You will not get it back. In a large jar it can be a third of the wax, which at our prices is a real amount of money going nowhere.
It is almost never a manufacturing fault. It is a habit, formed on the first evening, and it is entirely preventable.
Wax remembers
The first time you light a candle, the flame melts a pool of wax around the wick and that pool spreads outward. When you blow it out, the pool sets — and the diameter it reached becomes, for practical purposes, the maximum diameter it will ever reach again. Every subsequent burn follows the boundary the first one drew.
This is usually called wax memory, which sounds like folklore and is in fact just thermodynamics with a nice name. Set wax at the edge is a heat sink. The flame has to overcome a ring of cold, hard wax that it did not have to overcome on night one, and it generally cannot.
Light a new candle for twenty minutes and you have not saved it for later. You have permanently made it a smaller candle.
The rule
On the first burn, leave it lit until the melt pool reaches the glass on every side. In our small jar that is around one hour. In the large jar — three wicks, wider vessel — closer to two. Then blow it out. From that evening onward the candle will burn edge to edge without being coaxed.
If your first burn is going to be a twenty-minute one, do not light it. Wait for an evening you are actually staying in for. This is the least demanding piece of advice in the world and almost nobody follows it.
The other three things
- Trim the wick to 5 mm before every single burn. An untrimmed wick mushrooms, the flame grows, and you get soot on the glass and a shorter burn overall. Nail scissors are fine.
- Never burn longer than four hours. Past that the vessel gets genuinely hot, the wax overheats and the scent throw drops. Blow it out, let it set, light it again.
- Keep it away from a fan or an open window. A draught pulls the flame sideways, the pool goes lopsided, and you get a candle that burns down one side like a bad haircut. In an Indian flat with a ceiling fan on, this is the most common cause of a ruined candle we hear about.
If it has already tunnelled
There is a fix, and it works. Wrap aluminium foil over the top of the jar, leaving a hole above the flame, and burn it for an hour or two. The foil traps heat against the wall and re-melts the ring. Take it off, let it set level, and you have effectively given the candle the first burn it should have had. Watch it while you do this — a covered candle is a hotter candle, and it should not be left alone.
Written by The Bath Aura. If something here is wrong, or you know better — several of you do — tell us. We would rather correct it than defend it.