Diagnostics
When a candle burns wrong, this is the tree.
Half of what looks like a defect is a signature of natural wax. The other half is a wick or pour problem hiding as a cosmetic complaint. Learning which is which saves you from reformulating a recipe that was already fine.
Why does frosting form on soy candles (and how to prevent it)
Frosting on soy is crystallisation, not a fault. It appears more on candles cooled in a warm room and disappears the moment the surface melts. To reduce it, cool the pour more slowly by warming the vessel and the room to around 22°C before you pour, and avoid moving the candles while they set. To eliminate it completely you need a paraffin blend, which is a wax choice, not a defect fix.
The cosmetic signatures of natural wax you can ignore
Small wet spots on the shoulder of a jar are contraction marks, cosmetic only. Faint jump lines on the glass are where the pour paused for a second while you adjusted a wick. Neither affects the burn. If a customer asks, tell them the truth. Natural wax moves. That is why it is called natural wax.
How to fix soot, heat marks and burn defects
Soot on the glass rim is over-wicking or over-fragranced, in that order. Check the flame height first. If it is above 35 mm, drop a wick size. If it is in range and you still see soot, drop the fragrance load by one percentage point.
Heat marks on the glass, not to be confused with jump lines, look like brown scorching near the rim. This is a real safety issue. The vessel is running above its rated temperature and the glass will eventually fail. Drop a wick size immediately or move to a taller vessel.
The one-variable rule
When you fix a defect, change one thing and re-run the 4-burn protocol. Change two things and you are guessing which one worked. I know it feels slow. It is the only way to build a range you can defend when a customer asks why batch nine burns differently from batch three.
A diagnostic loop that changes one thing at a time takes twice as long and teaches you ten times as much.
| Symptom | Likely cause | Fix | Prevent |
|---|---|---|---|
| Soot on the rim, black tips on the flame | Over-wicked, or fragrance load above the wax's peak | Drop one wick size; if flame still >35 mm, cut fragrance by 1% | Confirm flame height between 25 mm and 35 mm on burn 2 |
| Frost bloom on soy surface | Rapid cool, disturbed set, or wax crystallisation signature | Cosmetic only. Warm-room pour (>22°C) reduces recurrence | Do not move vessels until fully set; log ambient temperature |
| Brown scorch near the glass rim | Vessel running above rated temperature — real fire risk | Drop a wick size immediately or move to a taller vessel | Probe rim on burn 3; abandon wick if rim exceeds 80°C |
| Jump lines mid-vessel | Pour paused mid-fill while adjusting the wick | Cosmetic only. Pour in one continuous motion next batch | Set wick and vessel before the wax hits pour temperature |