Yes, a tunneling candle can usually be fixed. Candle tunneling is a narrow hole melting down the middle with a wall of wax left around it. In a bought candle that has already been tested, the usual cause is burns too short for the melt pool to reach the edge; the other is a wick too small for the container.
Makers testing new candles look at the wick first. CandleScience, which supplies wax and wicks to candle makers, defines tunneling as a narrow melt pool forming in the center and burning down quickly, "leaving a large amount of wax on the sides of the container," and its first suspect is a wick too small to generate enough heat. It adds that an oversized wick can also "melt right down the middle," though it calls that "a less common occurrence."
Short burns are the usual cause
Blow a candle out after half an hour and the pool hardens well short of the glass, leaving a shelf of unmelted wax that the next short burn won't reach either. The National Candle Association (NCA) advises: "Avoid short burns." Lit only for brief periods, it explains, the wax can't melt completely.
When a melt pool falls short of the edge, let the candle burn 3–4 hours at one lighting, especially in its first few burns. By then the pool should come within about ¼ inch of the edge, according to CandleScience's burn-test instructions, which set the ceiling as firmly as the floor: always put the candle out after 4 hours. Burning longer, which makers call power burning, can overheat the container to the point of breaking.
Is a ring of wax on the sides always a tunnel?
Not early on. Melt pools form more slowly in the first few burns, because most of the flame's heat escapes out the top of the jar. As the wax level drops, more heat stays inside and the pool widens on its own. Judge a candle only after its fourth burn, and carry on if the wax left on the sides after the first couple of burns is about ⅛ inch thick or less.
A true tunnel looks different. It's a deep, narrow well with a wall of wax much thicker than ⅛ inch, and the wall doesn't thin out from one burn to the next.
How do you fix candle tunneling?
For a candle that has started to tunnel from short burns:
- Trim the wick to ¼ inch before lighting, as the NCA advises for every burn.
- Light it only when you can stay with it for 3–4 hours, and never leave it unattended.
- Let it burn until the pool reaches as close to the edge as it will, then put it out, keeping to the 4-hour limit.
- Repeat the same long burns for the next few lightings; the wall usually thins as the wax level drops.
- Leave the wax alone while it's hot. The NCA warns that pushing soft wax down risks burns and shortens the exposed wick, which can leave more wax behind next time.
Some candles still won't catch up. If the pool never reaches the edge after four or more full-length burns, the wick is probably undersized for the container, which is a question for the maker. The NCA also asks buyers to accept a certain amount of leftover wax, which it says keeps the candle from running too hot and varies with room temperature and burn time.
We'd skip home remedies that wrap the glass to trap extra heat. Trapping more heat raises the risk the burn-test guidance warns about: an overheated container can crack.
Soy candles, glass cloches and the last half inch
Soy wax has a few quirks worth separating from tunneling. After a burn, a soy candle often sets with a rough, bumpy top, because the melt pool cools unevenly; CandleScience calls that a feature of soy wax that doesn't affect how the candle performs. A whitish frosting on the surface is also cosmetic.
Our 11 oz California Garden Candle is soy wax on a cotton wick, and it comes with a glass cloche over it (it's also in our Citrus Lovers flight). Its listed burn time is about 60 hours with a trimmed wick. Lift the cloche off before lighting and set it well away from the flame. Put it back only once the candle is out and the wax has fully set; the NCA's rule is not to touch or move a candle until the wax has completely cooled. At 3–4 hours a sitting, 60 hours works out to somewhere between 15 and 20 long burns, and keeping each one long is what keeps the pool wide.
Stop for good when about ½ inch of wax remains in the container, the NCA's margin for jar and container candles (FAQs). The cloche outlasts the candle; we've written about a few ways to use it again, from a small terrarium to a dome over dried petals.
Photo by Paolo Nicolello on Unsplash.
