How to Tell If Your Candle Wick Is Too Big or Too Small
You poured your candle, let it cure, lit it for the first time — and something just looks off. Maybe the flame is roaring higher than it should, or maybe it's barely a flicker struggling to stay alive. Either way, the culprit is almost always the same thing: your wick size is wrong. Getting candle wick sizing right is one of the trickiest parts of candle making, especially for beginners.
If you've already gone through our guide on types of wicks for candles, you'll know that every wick series — cotton, ECO, CD, HTP, wooden — behaves differently depending on your wax, fragrance load, and container diameter. A wick that works perfectly in a 3-inch jar might be completely wrong in a 4-inch tumbler. This post focuses on helping you diagnose what's happening with your candle right now, so you can fix it before your next pour.
Below, we'll walk through the exact symptoms of a wick that's too big and a wick that's too small. Think of it as your quick wick size guide — no guesswork, just clear signs to look for and what to do about each one.
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When Your Wick Is Too Big: What to Look For
A wick that's too large for your container or wax type will burn hotter and faster than it should. The symptoms are usually obvious once you know what you're looking for.
1. Mushrooming (Carbon Buildup at the Tip)
After your candle has been burning for an hour or two, take a look at the tip of the wick. If you see a small black ball or mushroom-shaped glob of carbon forming at the top, your wick is likely too big. This happens because the wick is drawing up more wax than it can fully combust. The unburned carbon accumulates at the tip instead of burning cleanly.
Some mushrooming is normal with certain wick types, but excessive buildup — especially if it causes the flame to flicker erratically — is a sign you need to size down. Always trim your wick to about ¼ inch before each burn, but if mushrooming keeps coming back severely, trimming alone won't solve it.
Quick Fix: Try the next wick size down in the same series. If you're using an ECO 6, switch to an ECO 4 (like the ECO 4 Wicks for Candle Making) and test again.
2. Sooting and Black Marks on the Jar
Black soot staining the inside of your jar — especially around the top edge — is one of the clearest wick too big symptoms. When the flame burns too hot, it produces incomplete combustion, which releases soot as a byproduct. This discolors your container and can be a sign that your candle is releasing potentially harmful particulates into the air.
A small amount of soot can also be caused by drafts or fragrance oils with low flash points, so rule those out first. But if your candle consistently soots even in a still room with a tested fragrance oil, the wick is almost certainly too large.
Quick Fix: Size down one step and re-test. Also ensure you're trimming the wick before every burn.
3. Flame Is Too High
A healthy candle flame should be about ½ to 1 inch tall and relatively steady. If your flame is dancing above 2 inches, throwing off heat you can feel from several feet away, or flickering dramatically without any draft in the room, the wick is too big for the job.
A dangerously high flame is also a safety concern. It can overheat the container (especially glass), cause wax to boil or bubble, and increase fire risk.
Quick Fix: Blow out the candle, let it cool completely, and re-test with a smaller wick in your next pour. Do not try to trim the wick down mid-burn to compensate — it rarely fixes the root problem.
4. Excess Smoke
While a small amount of smoke when you first light a candle is normal, continuous smoking throughout the burn — or heavy smoke when you extinguish it — is a sign of incomplete combustion driven by an oversized wick. If your candle is pumping visible smoke into the room, something is wrong.
Quick Fix: Extinguish the candle by dipping the wick into the melt pool and lifting it back up (this reduces smoking on extinction). For the root cause, size down your wick.
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When Your Wick Is Too Small: What to Look For
A wick that's too small is the opposite problem — it doesn't generate enough heat to melt the wax properly. The signs are subtler but just as damaging to your final candle.
1. Tunneling
This is the most common and frustrating symptom of an undersized wick. Instead of creating a full melt pool across the entire surface of the candle, the flame only melts a small tunnel of wax straight down the center. The surrounding wax stays solid, and over time the wick gets buried deeper and deeper until it extinguishes itself.
We cover this in detail in our candle tunneling fix guide, but the short version is: tunneling is often a wick sizing problem at its core. A wick that's too small simply can't generate enough heat to reach the edges of the container.
Quick Fix: Size up to the next wick in the series. For a 3-inch diameter jar, your melt pool should reach edge-to-edge within 2–3 hours of the first burn.
2. Weak or Incomplete Melt Pool
Even if full tunneling hasn't set in yet, a shallow or incomplete melt pool is an early warning sign. After 2–3 hours of burning, your melt pool should be at least ¼ inch deep and should reach within ½ inch of the jar walls. If the wax around the edges is barely melted or the pool looks thin and uneven, your wick isn't pulling enough fuel.
This also affects scent throw — if the wax isn't fully melting, your fragrance oil isn't releasing properly, and your candle will smell weak.
Quick Fix: Size up one step and re-test with a fresh pour. Check your melt pool at the 2-hour and 3-hour marks.
3. The Wick
Frequently asked questions
- The most important factor is your container's diameter. Measure across the inside of your jar in inches, then use a wick size guide for the specific wick series you're using (ECO, CD, HTP, etc.). Most manufacturers publish recommended diameter ranges for each wick number. Always test with a small pour first before committing to a full batch.
- If the candle hasn't been burned much, you can sometimes re-melt it, remove the old wick, and re-pour with a new one. For a candle that's already been burned down significantly, it's easier to use it as a learning experience and correct the wick size in your next batch.
- Mushrooming happens when the wick draws up more wax than the flame can fully burn, leaving unburned carbon at the tip. It's often a sign your wick is too large for the container or wax type. Always trim your wick to ¼ inch before each burn, and if mushrooming keeps occurring heavily, try sizing down one step.
- Most experienced candle makers recommend at least 3–5 complete burn cycles to evaluate a wick. Check the flame height, melt pool depth and width, mushrooming, soot, and scent throw at each burn. Don't judge a wick after just one burn — behavior can change as the candle burns deeper.
- Yes, significantly. Soy wax typically requires a larger wick than paraffin because it has a higher melt point and burns cooler. Coconut wax behaves differently again. Always check whether the wick series you're using is designed for your wax type — for example, CD and ECO wicks are popular for soy, while HTP wicks work well across paraffin and soy.
- ECO wicks are made from cotton and paper braid, giving a consistent, clean burn — great for soy wax. CD (coreless cotton) wicks are designed to minimize mushrooming and work well in container soy candles. HTP wicks are rigid and self-trimming, making them popular for both soy and paraffin applications. See our full guide to [types of wicks for candles](/blog/types-of-wicks-for-candles) for a deeper comparison.
How do I know what wick size to use for my candle jar?
Can I fix a candle that already has the wrong wick?
Why is my candle wick mushrooming?
How many test burns should I do before finalizing my wick choice?
Does the type of wax affect wick sizing?
What's the difference between ECO, CD, and HTP wicks?
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