You buy a lovely candle, burn it for twenty minutes here and there, and within a fortnight there is a narrow shaft down the middle with a thick ring of unburnt wax around the outside. Half the candle you paid for will never burn.
That is tunnelling, and it is caused entirely by how a candle is used rather than how it was made.
Wax memory, and why the first burn decides everything
Container candles behave as though they remember. The first time you burn one, the wax melts outward from the wick to a certain diameter and then you blow it out. Every subsequent burn tends to melt to roughly that same diameter and no further.
So if your first burn only melted a small circle, the candle has effectively set its own boundary, and the wax outside it will stay solid however long you burn it afterwards.
This is why the first burn matters more than all the others combined.
The one hour per inch rule
The practical version. On the first burn, keep the candle lit until the melted wax pool reaches the edges of the container all the way round. For most candles that takes roughly one hour per inch of diameter.
A small jar candle might need an hour or so. A wider one such as our tall glass jar candles will want longer. The rule is not the clock, it is the edge: burn until the pool reaches the glass, then you can put it out.
The practical consequence is that a candle is a poor choice for a ten minute moment on the first outing. Light it when you have an evening.
Why an untrimmed wick makes it worse
A long wick produces a larger, hotter, more turbulent flame that consumes wax quickly and unevenly, and it produces soot that blackens the glass.
Trim the wick to around five millimetres before every burn. Trimming is the single most effective candle habit and it takes three seconds. If the wick has a mushroom of carbon on the end, that is a wick asking to be trimmed.
Trim it cold rather than hot, and remove the trimmings from the wax before relighting.
The foil method for a candle that has already tunnelled
Genuinely effective and worth knowing before you throw a candle away.
Take a piece of kitchen foil and wrap it around the top of the container, folding it inward over the rim so it forms a dome with a hole in the middle above the wick. Light the candle and let it burn with the foil in place.
The foil reflects heat down onto the unburnt wax at the edges, melting it back into the pool. After an hour or two the surface should have levelled. Remove the foil carefully, since it will be hot, and let the candle cool flat.
You may need to repeat it once. It does not work on a candle that has tunnelled so deeply that the wick is below the surrounding wax, since the flame cannot reach the edges at all.
Draughts, and why a windowsill is the worst place
A draught pushes the flame to one side, which melts the wax unevenly and causes the candle to burn down at an angle. It also makes the flame flicker and smoke.
British windowsills are the classic offender, since even a closed window in an older house moves enough air to affect a flame. Next to a door, under a wall vent, or near a radiator with rising convection are the other three.
If a candle is burning down one side, move it before assuming the wick was badly set.
The four hour limit
The other end of the problem. Burning a candle for too long causes the container to overheat, the wax to become too fluid and the wick to drift or mushroom.
Four hours is the usual maximum for a container candle. Put it out, let it cool completely, trim the wick, and light it again if you want more.
When a candle is genuinely finished
Stop burning when around a centimetre of wax remains in the base. Below that the container gets hot enough to be a genuine hazard, particularly with glass.
The remaining wax is not wasted. Warm the jar gently in a bowl of hot water, lift the wax out, and use it in an oil burner as a wax melt, which extracts the last of the fragrance safely.
Choosing a candle that is less likely to tunnel
Narrower containers tunnel less, simply because the pool has less distance to travel. Our small glass jar candles are more forgiving of short burns than the tall ones, which is worth knowing if you are the sort of person who lights a candle for half an hour.
Our full candle range covers three sizes in four fragrances.
Questions people ask
Why does my candle tunnel?
Because the first burn did not reach the edges of the container. Wax has a memory, so subsequent burns melt to roughly the same diameter as the first, leaving a solid ring around the outside.
How long should the first burn be?
Until the melted pool reaches the edges of the container all the way round, which is roughly one hour per inch of diameter. Judge by the edge rather than the clock.
How do I fix a tunnelled candle?
Wrap foil around the top, folded inward to form a dome with a hole above the wick, and burn for an hour or two. The reflected heat melts the edge wax back into the pool.
Why should I trim the wick?
A long wick makes a larger, hotter, more turbulent flame that burns wax unevenly and produces soot. Trim to around five millimetres before every burn, while the candle is cold.
When should I stop burning a candle?
When about a centimetre of wax remains, since below that the container can get dangerously hot. Warm the jar and lift out the last wax to use as a melt in an oil burner.
