Tunnelling is one of the most common problems in the manufacture and use of candles. The candle burns only in the middle, leaving hard wax on the sides and creating a deep "tunnel". Not only does this not look nice, but it unnecessarily shortens the life of the candle and wastes wax.

Good news? Tunneling is easily prevented - and often repaired - in most cases. Let's talk about why it occurs and what to do about it.

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What is candle tunneling

Tunneling means that the entire surface of the candle does not melt when it burns, but only the center around the wick. The cold, unwoven wax remains on the sides.

A properly burning candle should create an even bath of melted wax up the sides of the container.

Why a candle tunnels

Tunneling has several typical causes. Often multiple factors combine at once.

• Wick too weak

Most common reason for tunneling. The wick does not have enough power and the flame does not generate enough heat, because of this the wax only melts in the middle.

• Poorly chosen wick to wax type

Each wax burns differently. Soy and canola waxes usually need a thicker wick or multiple wicks, paraffin wax burns more easily. If you use the same wick for different waxes, the result can vary greatly.

• Too short a first burn

The first lighting of a candle is absolutely crucial. If you blow out the candle before the wax has melted all over the surface, the candle will "remember" the narrow tunnel and the tunnel will only get deeper the next time it burns.

The rule of thumb is: 1 hour of burning per 1 cm of candle diameter. Therefore, after the first lighting you have to let the candle burn longer.

• Drafts and cold environments

An open window, a draft, or a cold room affect the proper burning of a candle. The flame deflects or burns low and the heat is not distributed evenly.

How to prevent candle tunnelling

• Always choose the correct wick for the diameter of the candle, take into account the type of wax and consider multiple wicks for wider candles. If you are hesitating between two sizes, a slightly thicker wick is often better.
  
  
• Give the candle plenty of time when it first burns. Let the candle burn until the wax melts to the walls. This will set the proper foundation for all subsequent ignitions.
  
  
  
  
• Trim the wick before lighting. The ideal length is 3-5 mm. Long wick = unstable flame.
  
  
  
  
• Let the candle burn without a draft. Stable flame = even wax melting

How to fix a tunneling candle

Even if the candle is already tunneling, it's not lost yet.

💡 The foil method

1. Wrap the top of the candle with foil
2. Leave a hole above the wick
3. Light the candle and let it burn

The heat will bounce back and the wax will gradually melt down to the edges.

💡 Using a Heat Gun

• Gently heat the wax surface
• level the top layer

Ideal mainly for candles in glass containers.

➡️ Continuing the series:

In the next installment, we'll take a look at why a candle smokes, sputters or goes out and how to fix these problems.