Candle Making

How to Fix Candle Tunneling

Tunnelling — when a candle burns straight down the middle leaving a ring of unused wax — is one of the most common candle faults. The good news: it's almost always preventable once you understand the cause.

What causes tunnelling

Tunnelling usually comes down to wick size. An undersized wick can't create a full melt pool, so it burns a narrow tunnel and wastes the surrounding wax. The first burn matters most: if a candle isn't allowed to melt all the way to the edges on its first use, it 'remembers' that smaller pool every time after.

How to fix a tunnelling candle

For a candle that's already tunnelling, the wrap-in-foil method can help: wrap foil around the top, leaving an opening, and let it burn until the surface levels out. But the real fix is prevention — getting the wick right from the start.

Get the wick right

Wick size determines the melt pool, mushrooming, soot, and burn time. The only reliable way to size a wick is testing: try three wick sizes per container, wax, and fragrance combination, burn each for four hours, and check that the melt pool reaches the edges. A proper melt pool is full diameter and about 0.5–1cm deep.

Other common faults

Sinkholes form as soy wax cools and shrinks — fix them with a small second pour of remelted wax. Frosting is a natural characteristic of soy, not a defect. Wet spots, where the candle pulls away from the glass, are cosmetic only and can be reduced with a slightly lower pour temperature.