Candle Tunneling: Why it Happens and How To Fix it

Updated 6/25/24

Even the best, most tried-and-true scented candles can sink in the middle. It’s called “tunneling” — when you don’t burn a new candle long enough to allow the entire surface to melt evenly, the wax pool only melts in the center, forming a “tunnel” or sinkhole straight down the middle. It’s especially prevalent with larger candles with a wider surface area. Here’s everything you need to know about tunneling and the candle care techniques that prevent it.

Problems Caused by Candle Tunneling

• As the wick sinks and melts the surrounding wax above, the wax can drown the wick and make it hard or impossible to light.
• The candle’s lifespan is shorter because the unmelted wax doesn’t get used.
• Perfectly good, unused wax remains stuck to the sides of the candle container after the candle has burned down.

How To Prevent Tunneling

The first time you light a candle, allow it to burn long enough to melt the wax to the edge of the container (or within 1/4 inch), creating a full melt pool. This first lighting is called a “memory burn” since the candle remembers its first melt pool. Depending on the size of the container, melting the entire top layer of a new candle’s hard wax can take several hours (roughly one hour for every inch in diameter).

Doing this every time you light it will help the candle burn evenly throughout its lifespan, but the initial burn is the most important because of how hard the wax is when you first buy a candle. Another way to prevent candle tunneling is to always trim the wick to 1/8 inch (for wooden wicks) or 1/4 inch (for cotton wicks) before each use. Otherwise, carbon buildup will cause the candle to smoke, throw soot, and burn too hot, which can also cause tunneling.

How To Fix Candle Tunneling

The Foil Method

A candle topper can do this, too, but here’s how to DIY it:

1. Cut a square of tin foil slightly wider than your candle.
2. Fold the square in half and cut a circle out of the center, leaving an inch or two of foil around it (more or less, depending on the size of the candle’s container). 
3. Open the square flat again and lay the foil on the tunneled candle with the hole centered over the flame. Fold the edges of the foil down to hold it in place.
4. Light the candle wick. The foil will let the flame slowly melt the excess wax off the sides. If this drowns the wick, blow out the flame and use a cotton ball to remove some of the melted wax. Relight, let the wax melt again and repeat as necessary with the liquid wax. Once the candle wax surface is level, wait at least 24 hours for the wax to fully harden before relighting.

The Hair Dryer/Heat Gun Method

A heat gun is best, but a hair dryer will do in a pinch:

• Turn on the hair dryer or heat gun and melt the top of the candle in a circular motion, turning it with the other hand as you go. Be careful, and use an oven mitt if necessary.
• As the leftover wax melts down from the sides of the candle, it may drown the wick. If this happens, use a cotton ball to remove some of the melted wax.
• Continue until the candle surface is level.
• Wait at least 24 hours for the wax to fully harden before relighting.

Prevention is Key

The easiest way to avoid tunneling is to keep it from happening in the first place by doing a memory burn on the first lighting, always trimming the wick, and keeping it lit long enough during each burn. But don’t worry if only 1/4 inch of wax remains on the sides after the first burn. Since the flame creates more heat as a candle burns down, most of that wax should melt by the time the candle is spent. But if your candle does tunnel, now you know how to fix it with some aluminum foil or a little heat!

Getting the Perfect Burn

Every candle lover should know how to prevent and fix candle tunneling. Uneven burning can drastically reduce the lifespan of your candles and lead to wasted wax. Addressing poor candle burning habits, such as not allowing a full melt pool or neglecting to trim the wick, you can significantly increase your candles’ burn time and ensure a clean, even burn.

Let a container candle melt all the way to the edge of the candle jar — especially on the initial burn and, ideally, on each subsequent burn. This is the best way to keep candle tunneling issues from reducing burn time. But if you didn’t, it’s not too late: The foil method (or trying a candle topper), hair dryer, or heat gun are all you need to fix that candle tunnel and get the most out of your favorite candle!

The Glow Co.’s sustainable soy candles are thoroughly tested to prevent tunneling. If it does happen, though, and you need more guidance, please reach out! I’m happy to help.