Ensure to burn your candles for 2 hours first time you light it so that the whole top melts to avoid pooling and to get a good scent throw.
Do not burn for longer than 3 hours.
How to prevent candle tunneling
The first time you light the candle, don't trim the wick. This is the only time I advise not trimming the wick before you light a candle. If you trim the wick too short, the flame might be too small to melt all the wax.
Let the candle burn long enough to melt the top level entirely. This takes about an hour per inch in diameter of the jar. So if a candle is 3" wide, let it burn for at least 3 hours. If it doesn't melt all the way to the edge don't panic, but get as close as you can. Sometimes the last 1/4" will burn as the candle goes down.
After the first burn, try to let the candle burn for long stretches as often as you can to keep a large opening and prevent tunneling later on.
How to fix candle tunneling
There isn't a very easy way to fix candle tunneling hence why we advise to follow the above step when you first light your candle. However, here's how you can try to fix a candle that has tunneled:
Put the candle inside a vase and let it burn for a few hours. The hurricane keeps the heat around the candle to help melt the excess wax.
You can also wrap the top of the candle in tin foil (with an opening at the top) to get the wax to melt while burning. You may have to carefully remove some of the liquid wax as you go to keep the flame from drowning out. Let the candle burn until the entire top becomes liquid wax about 1/4" deep. This resets the wax and decreases your chances of tunneling in future burn sessions. If you just remove the dry hard wax down to the wick, it will likely tunnel again the next time as the wax around the edge still has never melted.
If you can't fix the candle there's still ways to enjoy the fragrance. You can either place the candle on a candle warmer and melt the wax that way without lighting the candle. Though you won't be able to enjoy the sense of a burning candle, you will still be able to enjoy the fragrance.
You can also remove the dry, hard wax and place it on the top of a tealight warmer like a wax melt. This is another way to warm the wax without lighting the candle.
Candle Care & Safety
The use of candles requires caution and awareness of the associated risks, so please ensure you always follow these safety precautions:
Always burn within sight. Never leave a burning candle unattended.
Keep away from children, pets and flammable materials.
Avoid using in drafty areas, near an open window, air duct or fan.
Never use water or a lid to extinguish a candle.
Never move a burning candle. Ensure candle is extinguished, wax is solid and jar is cold before handling.
Ensure wicks are upright and trimmed to 7mm during use and each time candle is re-lit.
Do not burn your candle for more than 3 hours at a time.
Stop burning when 13mm of un-melted wax remains in the bottom of the glass as the glass can overheat and explode.
Glass may become hot. Burn candle on an appropriate flat heat-resistant surface.