Why is my candle tunneling, and can I fix it?

Updated October 2026

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Read the tunnel before you change anything Why a tunnel gets worse with every burn Rescuing a candle that has already tunneled Keeping the next batch from tunneling When the pool still falls short, resize the wick References

A candle tunnels when the flame melts a narrow well down the middle and leaves a wall of solid wax around the edge. The usual cause is a wick too small for the jar's diameter. The next most common is a run of short burns that never let the melt pool reach the glass. Less often, an oversized wick burns straight down the center, a case CandleScience lists alongside the undersized one [1]. This page helps you tell which of these you have from what the candle shows, rescue a candle that has already tunneled, and set up the test that keeps the next batch from doing it.

Read the tunnel before you change anything

NI Candle Supplies describes the undersized case plainly: "only a little bit of the wax around the wick melts, leaving a lot of unmelted wax around the edges" [4]. The fix depends on the cause, though, and two of the causes call for opposite wick changes. Look at the candle, and at your notes from earlier burns, before you touch the wick size. The melt pool is the layer of liquid wax around the flame; "hang-up" is the ring of wax left on the glass.

What you see	What it most likely means	What to do
The pool stops well short of the glass at hour 3 to 4, burn after burn; the flame is small and steady	The wick is too small for the diameter. CandleScience expects the pool to be within 1/4 inch (6 mm) of the edge at three to four hours [3], and Supplies for Candles lists a pool that misses the edge in 3 to 4 hours, and tunneling itself, as signs to go up a size [2]	Go up one size in the same series [1]. Change nothing else for that test
A ring of wax on the glass in the first burns that is gone by the third or fourth	Normal hang-up. CandleScience calls a little hang-up "completely normal" and expects edge wax to melt down by the third or fourth cycle [3]	Keep burning full sessions. Do not resize on one burn
A deep, narrow well that drops fast, with a tall or moving flame and a hot jar	The wick is too large and is burning straight down. CandleScience says an oversized wick can melt straight down the center, and that if a larger wick made the pool smaller you should go down a size [1]. Its wick page ties oversized wicks to soot, flame movement and a container that gets too hot [9]	Go down one size. Check the jar temperature next burn
One side melts to the glass and the other side does not	An off-center wick, or a draft pushing the flame one way. Supplies for Candles names drafts and wick placement among the causes of lopsided pools [5]	Re-center the wick on the next pour; burn out of drafts
A candle that tested well tunnels at a customer's home	Short first burns. Supplies for Candles names short first burns as a cause [5]	Rescue it (below) and tell customers how long the first burn should be
Tunneling started after you changed fragrance load, dye or wax	The change altered how much fuel reaches the flame. Supplies for Candles says "even a 1-2% change can impact performance" and that a higher load may need a bigger wick [2]; CandleScience's wick recommendations assume 7.5 percent fragrance and no dye [9]. A new wax can move it either way: CandleScience says its coconut apricot wax flows through the wick faster than soy and generally needs a smaller wick [10]	Treat it as a new candle and retest the wick

Why a tunnel gets worse with every burn

Once a well forms, the flame sits below the rim of solid wax around it. Less heat reaches the outer wax, so the next pool is no wider than the last, and the well gets deeper. The walls also shield the flame, and in a deep well the liquid wax can rise around the wick until it drowns (see a candle that keeps going out). Makers describe this as the candle "remembering" its first pool. None of the suppliers cited here gives a figure for that effect, so treat it as a description of what you will see rather than a measured rule. Reading the melt pool covers how to judge a pool over several sessions.

Rescuing a candle that has already tunneled

These are ways to save a candle you own or one a customer brings back. They do not fix a wick that is wrong for the jar; that needs a new pour and a new test.

A shallow tunnel: burn it longer

Village Craft & Candle's advice for a tunnel is to burn the candle longer so the pool can reach the edge, and to cut off the ledge if needed [6]. Light it when you can watch it for the whole session, let the pool spread, and stop at the four hour mark CandleScience sets for its own burns [3]. Never leave it burning unattended, which the National Candle Association (NCA) lists as a basic rule [8]. If the pool has not reached the glass in four hours, the wick cannot do it on its own and the next method applies.

A deep tunnel: the foil collar

NI Candle Supplies publishes a foil method for deeper tunnels [7]. In its steps:

Light the candle for a few minutes to see how deep the tunnel is.
Tear off a sheet of aluminium foil about twice the diameter of the container.
Make a hole in the center "about the size of a 5 pence coin" (a little under an inch).
Crimp the foil around the rim into a dome, leaving the hole over the flame.
Keep at least 1 inch between the flame and the foil at all times.
Burn with the foil on for at least an hour, longer for a deep tunnel.
If the foil discolours or the flame grows large or smoky, lift the edges for air.
Remove the foil with a heat-resistant glove or utensil and let the wax cool before relighting.

The foil works by holding heat against the outer wax, which is also why it needs watching. The glass gets hotter than in a normal burn. One retailer's buyer protocol, Kohl's 100-Z, fails a glass or ceramic candle whose outside passes 175°F (79°C) in its tests [11]; you can check a rescued candle the same way using how hot the jar gets. Stop and remove the foil if the flame climbs toward it. This is one supplier's published method; none of the wax or wick makers cited here publishes it.

Your own test candle: let it fail

If a test candle tunnels, the result is the useful part. Record it and pour the next candidate rather than rescuing it. Village Craft & Candle's other fix, re-melting the wax and starting over with a larger wick [6], is a fair way to reuse unfragranced wax from a failed test, but a re-poured candle is a new candle and goes back to the start of the test.

Keeping the next batch from tunneling

Tunneling is settled at the bench, before anything is sold.

Size the wick by test. Pick a starting size from the wick maker's chart for your diameter, then test it with one size either side, as how to size a wick describes. CandleScience says not to judge the pool until at least the fourth burn cycle [3].
Use more than one wick when one cannot reach. Wide vessels may need two or three wicks; when a candle needs two or three wicks has the supplier method.
Trim before every burn. The NCA tells consumers to trim to 1/4 inch before each use [8]. A wick that is long one burn and short the next makes the pool hard to read.
Retest after any change. Load, dye, wax lot and vessel all move the wick (see what has to be retested).
Tell customers about the first burn. NI Candle Supplies tells buyers to let the first burn run until the pool is within a few millimetres of the edge, and gives its own times by size: up to 3 oz, 1 to 2 hours; 4 to 8 oz, 2 to 3 hours; 9 oz and above, 3 to 4 hours [7]. Those are its figures. Your test tells you how long your candle takes, and that number belongs on your care card (burn instructions to give customers).

When the pool still falls short, resize the wick

If a full, watched session still leaves wax on the glass, the candle needs a different wick, and the decision of up or down, or a different series, is the subject of when to change the wick size.

References

CandleScience, Soy Wax Troubleshooting Guide, undated (images dated 2021), read October 22, 2026. https://www.candlescience.com/wax/soy-wax-trouble-shooting-guide/
Supplies for Candles, The Complete Guide to Wick Testing: What Every Candle Maker Needs to Know, published February 26, 2026, modified September 2, 2026. https://www.suppliesforcandles.co.uk/the-complete-guide-to-wick-testing-what-every-candle-maker-needs-to-know/
CandleScience, How to Conduct a Basic Burn Test, undated, read October 22, 2026. https://candlescience.com/learning/how-to-conduct-a-burn-test/
NI Candle Supplies, The Only Candle Wick Guide You'll Ever Need, published June 24, 2025, updated September 17, 2026. https://www.nicandlesupplies.com/blogs/how-to-guides/the-only-candle-wick-guide-youll-ever-need
Supplies for Candles, Trouble Shooting, published October 15, 2025, modified August 26, 2026. https://www.suppliesforcandles.co.uk/trouble-shooting/
Village Craft & Candle (Erin Parsons), Top 10 Candle Making Problems and How to Solve Them, February 8, 2022. https://villagecraftandcandle.com/blogs/news/top-10-candle-making-problems-and-how-to-solve-them
NI Candle Supplies, How to Stop a Candle from Tunnelling: Causes, Prevention and the Foil Fix, undated, read October 22, 2026. https://nicandlesupplies.co.uk/blogs/how-to-guides/how-to-stop-a-candle-from-tunnelling-causes-prevention-the-foil-fix
National Candle Association, Candle Safety Tips, modified August 12, 2025. https://candles.org/candle-safety/
CandleScience, Candle Wick (category page and wick recommendations), read October 22, 2026. https://www.candlescience.com/candle-wick
CandleScience, Lab Notes: CandleScience Coconut Apricot Wax, undated (images dated April 2024), read October 22, 2026. https://candlescience.com/lab-notes-candlescience-coconut-apricot-wax
Kohl's, Private Brands Performance Claims Test Protocols 100, Protocol 100-Z: Candle (including freestanding, taper, tealight, votive, filled and novelty candles), revised February 2025 (current revision; candle limits unchanged from 100-Y, February 2023), read October 22, 2026. https://link.kohls.com/content/dam/klink/100-Z-CANDLE.pdf