Burn behaviour
Visible soot or black smoke
Sooting indicates incomplete combustion. It stains walls, soils lungs, and signals an over-wicked or over-fragranced candle. Treat as a safety priority, not a cosmetic issue.
Written by Maya Holloway
Likely causes
- Wick over-sized.
- Untrimmed wick (over 6 mm).
- Fragrance load too high or contains heavy aromatics.
- Draft causing flame instability.
How to diagnose
- Trim wick to 5 mm, retest in a draft-free space.
- Burn a control candle (same wax, same wick, zero FO) and compare.
What to change next batch
- 01
Trim wick to 5 mm before every burn and never burn longer than 4 hours.
- 02
Size down the wick.
- 03
Reduce fragrance load.
- 04
Remove draft sources within 1 metre of the candle.
Related symptoms
- Wick mushrooms and carbons up
Carbon ball on the wick tip, sometimes glowing red.
- Flame jumps, flickers, or pops
Unstable flame, often paired with crackling.
Read deeper
- 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.