Why is my candle tunneling?
Short answer
The wick is usually too small for the container, so the melt pool never reaches the edges. Short burns make it worse.
Explanation
In the book's wick test, a correctly sized wick melts the whole surface to the edges within 1.5–2 hours, with a melt pool about 1 cm deep. If there's no full melt pool after 2 hours, or the candle tunnels, the wick is too small, and the scent throw will be weak too.
How you burn matters as well. Each session should last 1.5–2 hours so the whole top layer melts, but no more than 3 hours at a time.
What to do
- Test the next wick size up for that container diameter.
- Record wick brand and size, jar diameter, wax and fragrance % for every test.
- Let each burn run until the full surface has melted.
Source: The Big Book of Sweet Dessert Candles — Which Wick Is Best? · Wick Testing · How to Burn a Candle Correctly