Wood Wick vs Cotton Wick Candles: What Actually Differs
Key Takeaways
- Both wicks do the same job. A wick is a fuel pump. It draws melted wax up by capillary action so the flame can burn it.
- Cotton wicks trim themselves as they burn, within limits. The dry tip of a braided cotton wick burns away. Some are also treated with flame-retardant salts so they burn at the right rate.
- Wood wicks stand out for their sound and look. They're flat strips of wood on a metal tab, and they give a soft crackle. We found no study showing they burn cleaner, longer or wider than cotton.
- The only comparison we could read in full can't settle the question. It burned one wood-wick candle and one cotton-wick candle from different brands. The wood-wick one released more of a fragrance additive, but the study can't separate the wick from the fragrance.
- Care differs slightly. Trim cotton to about 6 mm and wood to 3 to 5 mm before each burn. The long first burn applies to both.
Stand in the candle aisle and you'll find two kinds of wick. There's the familiar cotton string, and there's a flat strip of wood that crackles when it burns.
We use both. Our Signature and NOIR candles burn on wood wicks, and our Weekday range uses cotton. So we've had reason to look hard at what actually separates them, and where the evidence runs out.
Here's what each wick is, how it works, what the research says, and how to look after each.
What a wick actually does
A wick doesn't burn the wax directly. It pumps it.
When you light a candle, the heat melts the wax around the base of the wick. That liquid wax is drawn up the wick by capillary action, the same way a paper towel soaks up a spill. Near the top, the heat turns the wax into vapour, and it's the vapour that burns.
A doctoral study of heat and mass transport inside candle wicks describes the wick as a fuel pump (Raju, Case Western Reserve University, 2007). The wax vapour also cools the wick and protects it from burning away.
That's true of both wick types. What differs is the material doing the pumping, and what happens at the tip.
How a cotton wick works
A cotton wick is cotton fibre spun into threads, then braided together. The tiny gaps between the fibres, threads and braids act as capillaries. That's what draws the wax up.
Why cotton wicks trim themselves
As a candle burns down, more wick is exposed above the wax. The further the tip is from the melt pool, the harder it is for liquid wax to reach it. Eventually the tip dries out.
Raju's study explains what happens next. Without wax to cool it, the dry tip heats up sharply and burns away. The wick settles at a length where fuel supply and burn-off balance. This is called self-trimming, and it's why a cotton wick doesn't just keep getting longer.
Self-trimming has limits, though. It works during a burn, not between burns. A cotton wick still needs trimming before you light it, especially if it has mushroomed or curled.
What's added to cotton wicks
Plain cotton isn't the whole story. Researchers at Lund University note that ammonium phosphates and borax are added to wicks as flame retardants (Pagels et al., Journal of Aerosol Science, 2009; open copy). Their job is "to ensure that the wick is consumed at a sufficient rate and to prevent glowing of the wick upon extinction."
The same paper notes that some wicks have a metal core, such as zinc or tin, to keep them standing straight.
Lead was once used for that job. In Australia it's now banned. Candle wicks containing more than 0.06% lead have been permanently banned since 2002, whether sold on their own or in a candle (ACCC Product Safety). The ACCC says you can spot them "by a silvery or dark lead core in the fabric of the wick." Our cotton wicks are lead-free.
How a wood wick works
A wood wick is a thin, flat strip of wood, set in a small metal tab that holds it upright in the jar. It does the same capillary job as cotton. The wax travels up through the wood instead of between braided threads.
Ours are ACE+ wood wicks, made in the USA from sappy fruit trees. The version we use is 16 mm wide, with what the supplier calls an "additional boost strip". Our wick supplier lists it as suitable for soy and soy-blend waxes. They also say ACE and ACE+ wicks "tend to create a gentle crackling sound."
Why a wood wick crackles
That crackle is what sets a wood wick apart. It's a soft, irregular pop, a bit like a small fire.
We looked for a published study explaining exactly what causes it and didn't find one. You'll see explanations online involving moisture or sap in the wood. They may be right, but we couldn't find them tested, so we won't state them as fact.
Why wick width matters
A wood wick is sized by width, and the width decides how far the melt pool can reach. Our supplier rates the 16 mm ACE+ to melt a pool 71 to 80 mm across. The inside of our Signature jar is 74 mm across. The supplier adds that the fragrance, how much of it is used and room temperature all move the result, and that makers should test.
Wick sizing is decided by testing, not calculation.
What the research says about each
We found very little research on wick type, and the honest answer is that nobody has settled which is better.
One small study, and why it can't settle the question
A 2025 study in the journal Indoor Air measured a phthalate called diethyl phthalate (DEP) in candle and incense smoke (Moo et al., Indoor Air, 2025). The authors describe DEP as "widely used as a fragrance fixative for prolonged scent release".
Among their candles, the wood-wick one released more DEP than the cotton-wick one. The authors suggest this was "likely due to differences in combustion efficiency."
The detail matters here. The study tested one wood-wick product and one cotton-wick product. Both were scented paraffin candles, from different brands, and the paper doesn't say they shared a fragrance. So the study can't tell whether the difference came from the wick or from what was in the fragrance. The paper gives no separate figures for the two candles and no statistical test of the difference. The authors offer the combustion explanation as a likely cause, not something they measured.
The fragrance oils we use are phthalate-free. That's a fact about what goes into our candles. We haven't measured what comes out of them, and we haven't found anyone who has, so we won't claim a result.
What wick additives do to the smoke
The Lund University study burned two kinds of taper candle in a test chamber. During steady burning, most of the very fine particles were phosphates or alkali nitrates. The researchers traced these most likely to flame-retardant additives in the wick (Pagels et al., 2009).
That study had real limits. It tested two kinds of taper candle, one stearin and one stearin and paraffin. Neither was soy, neither was a container candle, and neither had a wood wick. It tells us wick additives can show up in the smoke. It doesn't tell us how wood and cotton compare.
We also couldn't find published data on what, if anything, is added to wood wicks. So we're not in a position to compare the two on additives either.
How to care for each
Most candle care applies to both wicks. The differences are small and practical.
| Cotton wick | Wood wick | |
|---|---|---|
| Trim before each burn | About 6 mm | 3 to 5 mm |
| How to trim | Wick trimmer or scissors; remove any mushroomed tip | Snap or trim off the charred edge |
| Lighting | Light the tip | Hold the flame close to the wax at the base of the wick |
| First burn | Until the melt pool reaches the glass | Same |
| Maximum burn | Four hours | Four hours |
Trimming. The National Candle Association recommends trimming wicks to about 6 mm (¼ inch) before every burn (National Candle Association). For our wood wicks we recommend 3 to 5 mm.
Lighting a wood wick. Our supplier's tip is to light it close to the wax rather than at the top. That melts the nearby wax so the wick can start drawing fuel.
The first burn is the same for both. Burn until the melted wax reaches the glass all the way round. That usually takes about an hour for every inch of jar width (National Candle Association). The same guide says not to burn a candle for more than four hours at a time. Cut it short and the candle can start to tunnel, whatever the wick. We've explained why candles tunnel and how to fix it.
Soot and draughts. Pagels and colleagues say "most soot emissions from candles can be avoided by using high-quality candles, trimming long wicks". They add avoiding air flow strong enough to make the flame flicker. That advice isn't specific to one wick type. Keep candles away from open windows, fans and air-conditioning vents.
Which should you choose?
Choose on sound and look, because the evidence doesn't separate them on anything else.
- Choose wood if you like the crackle and the look of a flat wick. It's the more distinctive experience.
- Choose cotton if you'd rather have a quiet flame. It's the braided wick you'll recognise.
Neither choice changes the basics. Whichever you choose, a well-sized wick, a proper first burn and a trimmed wick are the parts you control.
Something useful if you want to compare: our Weekday range shares five fragrances with five of our wood-wick candles. The Weekday candles use cotton wicks in tins. The wood wick candles use glass jars. So you can try one scent on each wick and decide for yourself. The vessel is different too, so it's not a lab test, but it's the nearest like-for-like we can offer.
If you're weighing up labels as well as wicks, we've written about what "non-toxic" on a candle label actually means.
Frequently asked questions
Are wood wicks safer than cotton wicks?
There's no good evidence either way. The only comparison we could read in full compared one wood-wick candle with one cotton-wick candle from a different brand, so it can't separate the wick from the fragrance. Both wick types need the same care: trim before lighting, never leave a burning candle unattended, and keep it away from draughts.
Do cotton wicks contain lead?
Not above 0.06% lead, in Australia. Wicks containing more than 0.06% lead have been permanently banned since 2002 (ACCC). Some cotton wicks have a zinc or tin core for stiffness. A silvery or dark core in the wick is the sign the ACCC tells you to look for.
Why won't my wood wick stay lit?
Check two things first: the wick may be too long, or it wasn't lit close enough to the wax. Trim it to 3 to 5 mm, snap off any charred edge, and hold the flame near the base of the wick until the wax around it melts. If it keeps going out on a long first burn, raise it with whoever made the candle.
Why does my wood wick crackle?
Crackling is normal for wood wicks. Our supplier says ACE and ACE+ wicks "tend to create a gentle crackling sound." We haven't found a published study that explains the exact cause, so we'd be wary of anyone who states one as fact.
Do wood wick candles tunnel less?
We couldn't find a study that compares them. Tunnelling comes down to how long each burn is and whether the wick is sized to the jar, and that's true of both types. Give the first burn enough time for the wax to melt to the glass.
Do wood wicks burn longer?
We found no evidence that they do. We found no study that measures burn time by wick material.
The bottom line
Wood and cotton wicks do the same job in slightly different ways. Cotton is braided, self-trims as it burns, and can be treated with salts to control how fast it burns. Wood is a flat strip that crackles, and it's sized by width to the jar.
The evidence on which is better is thin. The only comparison we could read in full looked at one candle of each, from different brands. So choose on sound and feel, trim before every burn, and give the first burn the time it needs.
Julia hand-pours every Yarra Light candle in Melbourne from 100% soy wax, with phthalate-free fragrance oils made in Australia. The Signature, NOIR and New Year ranges use wood wicks made in the USA, and the Weekday range uses lead-free cotton wicks. We sell both kinds, so we have a commercial interest in this topic. The care guidance here applies to any container candle, whoever made it.