Easy to avoid and a little less straightforward to fix, tunnelling is a common candle issue, albeit one that can be quite baffling, as the reason why a candle is tunnelling is less understood. The cause of candle tunnelling lies not in what you are doing currently, but what you did.
What is candle tunnelling?
Before diving into the cause and solutions to candle tunnelling, it might be worth taking a look at what candle tunnelling is, and why it is an issue. When a candle burns hollow, and leaves a thick, unused mantle (or rim), this is referred to as 'tunnelling'. The result is that the flame does not sit on top the candle, but slowly sinks down into the hollow.
Why is this an issue? As the flame sinks down, the air flow to the flame gets disrupted, as there isn't enough room for air to travel to the candle. This disruption can cause the candle to start smoking, which is something we always try to avoid as it means the candle isn't burning cleanly.
The other issue with candle tunnelling is that it leaves a great chunk of wax unburned, the remaining rim, which unless you melt it into a new candle, is simply wasted.
What causes my candle to tunnel?
It links back to a very specific and slightly peculiar feature of candle wax, which is that the wax has a 'memory'. This candle memory is set during the first burn of the candle, and so if that burn isn't done correctly, the candle is likely to tunnel.
The good news is that if you're burning a well-made, good quality candle then the issue of candle tunnelling can in most cases be remedied; it's just a matter of knowing the solution. So let's get started.
How to prevent a candle from tunnelling
Candle tunnelling can be avoided by 'setting the memory' of the candle. We do this by making sure the initial burn is long enough to melt the candle all the way to the edge. This is because the size of the wax pool during the first burn determines the life of the candle. Subsequent burns won't melt the wax beyond the initial wax pool, so if it didn't melt close enough to the edge of the candle, tunnelling might occur.Setting the memory of the candle (video)
How to set the memory of a candle: As a rule of thumb, burn a new candle for 1 hour per every 2.5cm (~1 inch) in diameter. So for a 7.5cm (~3 inch) diameter candle, the initial burn time should be at least 3 hours. Depending on the burn conditions (e.g. ambient temperature), it can take longer than this. Keep an eye on the candle and let it burn until the wax pool gets close to the edge. The video above shows how this works for our 7cm pillar candles.
How to fix a tunnelling candle
Once tunnelling has occurred, there are ways to fix it, depending on how far the tunnelling has progressed.
1. Hug the candle
If the tunnelling hasn't gone too far, a way to correct it is by 'hugging' the candle; pushing the soft wax rim inwards towards the flame, so that it has a chance to melt. The trick is to push the rim far enough inwards so it melts, while taking care not to push so hard that the rim breaks off.
2. Trim the rim
If the tunnelling has gone too deep to fix by hugging, the rim can be trimmed down with a sharp knife when the wax is warm. Be careful not to damage the rim or the candle might start dripping.
Alternatively, you can cut off the complete top of the candle and start the process of setting the memory all over again. Make sure you do not cut the wick off while doing so, and be careful when cutting through wax!
3. Melt the rim down
Another way to fix a tunnelling candle, without having to resort to sharp objects, is to use heat. Place the candle in a container that is tall and narrow enough to allow the heat to build up and bounce off the container walls. As the heat from the candle bounces back off the container walls to the candle, it can melt the rim back down to a point where tunnelling will no longer occur.
This method will take a little longer than cutting the rim, but as said it doesn't involve any cutting.
Hopefully the above tips can help you to avoid tunnelling of your candle, but as you can see even if tunnelling has occurred, there are still ways to fix it (provided that the issue was with the burning and not the quality of the candle itself).
Read our article on tips and best practices if you have more questions or would like to know more about how to burn candles. Alternatively, check out our online store for one of the most beautiful candle collections Australia has to offer.