What Causes Candle Wicks to Mushroom (How to Fix)

Mushrooming wicks can form from using the wrong wick size, wrong wick type, fragrance oil, wax additives, and candle burn time.

Mushrooming is not always the end of the world for your candle, but there are scenarios when it could be a sign of deeper issues that may affect the quality and safety of the candle.

This short article will cover the causes, how to fix it, and what to look for to avoid more significant problems with your candle.

The Causes of Mushrooming Wicks and How to Fix Them

Excess carbon buildup will cause black balls of carbon to form on the wick giving off a similar appearance to a mushroom cap.

This excess carbon is caused by an incomplete combustion process leading to the wick having difficulty burning the fuel (wax).

Let’s go over the factors that could lead to mushrooming.

Wick Size

The most common cause of a mushrooming wick is the size of the wick.

Wicks that are too large for the candle will consume more wax than its capable of burning, leading to heavy carbon buildup.

When you have a wick sizing problem and mushrooming, it’s most likely because the wick is too large. Too large of a wick will also be accompanied by a larger flame than usual, a sputtering flame, and excessive heat.

In rare cases, you can have a wick that is too small and cause mushrooming. If your wick is too small, you’ll also notice other problems, like the flame and melt pool being too small to melt the wax properly.

Pay attention to the other symptoms of the candle that are occurring to determine if the wick is too large or too small, and then adjust the size of the wick accordingly. I would start with one size up or down and adjust from there.

Wick Type

The type of wick that’s best for you depends on your wax, fragrance oil, and any additives you may add to your candle.

Some wick series are better for certain waxes and candle types than others.

If you’re having problems with the wick in addition to mushrooming, like excess soot and smoke, then you may want to look into a different series of wicks that may be more suitable for your candle.

Fragrance Oil

Fragrance oil can have an impact on the performance of your wick.

The viscosity of the fragrance oil can require either a larger or smaller wick than otherwise needed for that particular wax.

The fragrance load can also be a factor. If you like to use a fragrance load on the higher side (10%), you might want to try reducing that load.

A good baseline for testing is 1oz per 1lb of wax (6% fragrance load). If you’re not satisfied with the hot throw of the candle, you can begin testing a higher fragrance load and find the balance of a good hot throw while maintaining an optimal wick.


Just like fragrance oil, dyes and additional additives can change how your wax interacts with the wick.

You may have found a wick that’s an excellent fit for your candle, but once you add additional elements, the balance can change, and adjustments to wick size or type may be necessary.

Burn Time

Even if you have a “perfect” wick for a candle, if you burn it too long, you’ll end up with excess carbon buildup leading to mushrooming.

How long is too long will depend on the size of the candle.

Although you don’t want to burn a candle for 6+ hours, you should also avoid short burn times, which can lead to candle memory problems.

Wick Maintenance

Make it a habit to regularly trim your wick.

Trim your wick, and you’ll keep the candle flame stable and get the best burn quality from the candle.

Are Candle Wicks Supposed to Mushroom?

Some wicks are more prone to mushrooming, such as cored and CD series wicks.

Don’t let the mushrooming scare you away from these wicks.

There are benefits like rigidity, burn times, and compatibility with viscous waxes, so they’re still a great option. These wicks must be trimmed before each burn, which you should get into the habit of doing regardless of the wick type used.

Are There Any Risks to Ignoring a Mushrooming Wick?

More often than not, a mushrooming wick also has a flame too large for the candle. A larger flame than usual increases the heat generated by the candle and, in worst-case scenarios, can compromise the container.

In addition, mushrooming can lead to excess soot, dark smoke, and an unstable flame. An unstable flame increases the risk of a fire hazard, so ensure you trim the wick and remove any excess carbon buildup before you light the candle.


Candle wicks can mushroom due to the following:

  1. Wick size
  2. Wick Type
  3. Fragrance Oil
  4. Wax additives
  5. Excessive burn time

Trim the wick before lighting the candle to avoid additional problems arising from excess carbon buildup.

If mushrooming occurs consistently within the first 1-2 hours of burning the candle, then it’s time to address the issue. If mushrooming happens occasionally or after long burn sessions, then a simple trimming will do the trick.

When making candles keep detailed records of your wick, wax, fragrance, and additives. When trying to solve mushrooming, only adjust one variable at a time.

It may be tedious, but it’ll be worth ensuring your candles have a safe and quality burn.