Lets face it sometimes candles tunnel and it can be caused by many things. The main one i have noticed is, people dont let their candles reach the full melt pool on the first burn. Also dessert candles can be temperamental. Even being an experienced candle maker, i still find that sometimes my dessert candles just want to do their own thing and it cant be helped, especially if its under an air con or catching a draft of wind. So, how do you fix it? Ill attach a cool video for you to watch and all you need is some alfoil. If this fails scoop some wax out (use it in a melter) and relight and let it reach a full melt pool.
How to Fix a Tunneled Candle - YouTube
credit: @try_everly
Photo credit to Emily VanSchmus via better homes and gardens.