Burn behaviour
Wick mushrooms and carbons up
A mushroomed wick means the wick is delivering more fuel than the flame can burn cleanly. The carbon ball is unburned wax and FO. It causes sooting and is a fire-safety flag.
Written by Maya Holloway
Likely causes
- Wick is over-sized for the vessel.
- Fragrance load is too high or contains heavy resins.
- Wick brand mismatch (e.g. zinc-cored wick in a clean-burning blend).
How to diagnose
- Photograph the wick after a 2-hour burn. A small mushroom (2 mm) is normal; anything larger is over-wicked.
- Check for soot deposits on the inside of the vessel rim.
What to change next batch
- 01
Size down the wick one increment.
- 02
Drop fragrance load by 1 percentage point and retest.
- 03
Trim wick to 5 mm before every burn.
Related symptoms
- Visible soot or black smoke
Black trail off the flame, deposits on the vessel.
- Flame jumps, flickers, or pops
Unstable flame, often paired with crackling.
Read deeper
- Wick testing protocol: the 4-burn method
Wick testing is the difference between a candle that sells and a candle that smokes. Here's the 4-burn method.
- Candle fire safety: BS EN 15493 and a real burn-test protocol
BS EN 15493 sets the fire-safety bar. Here is the standard, plain English, plus a 4-burn test protocol.