Why your candle is tunnelling, and how to fix it

A candle tunnels when the flame melts a narrow well straight down the middle and leaves a thick wall of hard wax around the sides. It wastes most of the candle, weakens the scent and, as the tunnel deepens, drowns the wick. The fix most worth knowing is also the simplest: on every burn, and above all the first one, let the melted wax reach the edge of the container before you blow the candle out. If you want to know how to fix candle tunnelling in a candle that has already started, the honest answer is that a shallow tunnel can usually be evened out with patient, supervised burns, and a deep one often cannot.

Here is why it happens, what helps, and when to stop trying.

Why is my candle tunnelling?

The first burn was too short

Wax has what candle makers call a memory. The first time a candle is lit, the pool of melted wax sets the boundary for every burn after it. If you blow it out after twenty minutes, when only a small circle around the wick has melted, the next burn tends to stop at the same circle, and the next. Each time the well gets a little deeper, and the wax around it never melts at all.

Every burn is too short

Even a candle that started well will tunnel if it is only ever lit for a few minutes at a time. Short burns melt a small pool; small pools dig a hole.

The wick is too small for the candle

Some candles tunnel however carefully they are burned, because the wick simply cannot produce enough heat to melt wax all the way to the edge of a wide container. That is a design problem, not a burning problem, and it is more common in wide, cheaper candles and in some candles made with harder waxes.

Draughts and an uneven surface

A draught pushes the flame to one side and melts the wax unevenly. A candle on a tilted surface pools on one side. Both encourage lopsided tunnels.

How long to burn a candle the first time

Long enough for the melted wax to reach the edge of the container all the way round. A common rule of thumb among candle makers is around an hour for every inch (about 2.5 cm) of the candle’s diameter, so a small candle might need an hour or two and a wide one considerably longer. Check the label: many makers state a first-burn time.

There is an important upper limit. Safety guidance from the National Candle Association is not to burn a candle for more than four hours at a time. If a candle cannot form a full pool within that time, the candle is probably too wide for its wick, and you should not keep burning it for longer to compensate.

Plan the first burn for a time when you will be at home, in the same room, for the whole of it.

Should you trim the wick?

Yes, before every burn, once the candle has cooled. Trimming the wick to about a quarter of an inch (around 6 mm), as the National Candle Association advises, gives a steady, controlled flame. A long, untrimmed wick burns high and smoky, flickers, can mushroom at the tip and melts the wax unevenly, while also being a greater fire risk. Use wick trimmers or small scissors, and clear away the trimmings so they do not sit in the wax.

Keep the wick upright and centred while the wax is liquid, too. A wick that has leaned to one side will melt one side faster.

Can candle tunnelling be fixed?

Sometimes. It depends how deep the tunnel is.

A shallow tunnel

If the tunnel is only a centimetre or two deep and the wick is still standing well above the wax, give the candle a series of full burns: trimmed wick, a level surface away from draughts, and each burn left until the pool reaches as far towards the edge as it will go, within the four-hour limit. Over a few burns, the walls often soften and level out.

A deeper tunnel

Once the tunnel is deep, the flame sits low in a well, struggles for air, and cannot melt the walls above it. Burning it for longer and longer will not solve this and only makes the container hotter. A safer approach is to stop burning it and work on the wax when it is completely cool: carefully scrape or cut back the high walls of hard wax with a spoon or blunt knife so the surface is closer to level, without digging round the base of the wick. Then try a full, supervised burn.

What about foil and hair dryer tricks?

You will find plenty of popular hacks online for tunnelled candles: wrapping a collar of kitchen foil around the rim of a burning candle, or blasting the surface with a hair dryer or heat gun. Neither appears in the safety guidance of the bodies that set candle-safety advice, and both involve doing something improvised to a hot container or an open flame. I would not recommend them. If a candle cannot be rescued with ordinary careful burning, it has reached the end of its life as a candle.

Use the wax another way

The scented wax in a tunnelled candle is still useful without a flame. If you own an electric wax warmer, you can cut out pieces of cold wax and use them in it, following the warmer’s own instructions. Otherwise, the candle may still scent a room unlit, in a wardrobe or a drawer.

When to stop burning a candle

Stop, and do not relight it, when:

• the wick has drowned or is too short to stay lit;
• the flame is very large, smoking heavily or flaring;
• the container is cracked, chipped or becoming very hot to touch;
• there is about half an inch (around 1 cm) of wax left in the container, the point at which the National Candle Association advises stopping, because the heat can damage the container or the surface below.

Burning candles safely

Tunnelling is mostly about wasted wax, but every fix involves a lit flame, so the basic safety rules apply throughout. The National Fire Protection Association advises:

• never leave a burning candle unattended, and blow it out when you leave the room or go to sleep;
• keep candles at least 30 cm (about a foot) from anything that can burn, including curtains, books and bedding;
• use sturdy holders that will not tip over easily;
• put a candle out before it burns too close to its holder or container.

Stand candles on a stable, heat-resistant surface, out of draughts and out of reach of pets. Fire and rescue services around the world give much the same basic advice, so your local fire service’s guidance is worth a look too.

Buying candles that burn well

The best way to avoid tunnelling is to start with a candle that is designed to burn evenly. Wide containers need either a well-matched wick or more than one. Buy from makers who state a burn time and first-burn instructions, and treat a candle that tunnels from its very first careful burn as a fault worth mentioning to the seller.

Candles are one of the cheapest ways to change how a room feels, on an autumn evening or a slow Sunday afternoon, and a small part of making a rental feel like home. Burned properly, one good candle outlasts three bad ones.

Sources

• National Candle Association. Candle safety.
• National Fire Protection Association (NFPA). Candles.