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p-soot-consumption

P-05 soot index and consumption rate

2026-10-17 · By The Candle Bench · Repeats 2×

Two numbers that are always read together, because a candle that consumes slowly and smokes is worse than one that burns fast and clean. The soot index is a blind photograph score; the consumption rate is a weight measurement over the whole record.

MethodGravimetric consumption over the whole record plus a blind photographic soot scoreRepeats2×equip5Quantities produced3Environment controlSame room as the burn sessions, 21-24 C, 40-55 %RH; photographs under fixed 5000 K lighting

Procedure

  1. 01

    Weigh the fully cured candle before the record begins and again after the final session, at the same ambient condition, on the same scale.

  2. 02

    Photograph the top surface under fixed lighting after every second session: same distance, same angle, same exposure, no flash.

  3. 03

    Collect the soot from the 200 mm above the flame onto a white card held for one full hour in the last session of the record.

  4. 04

    Score the photograph set blind, against the written anchors: 0 is a white top with no deposit; 5 is a light grey ring at the rim; 10 is a black film over half the surface.

  5. 05

    Consumption is the weight difference in grams divided by total lit hours, reported to two decimal places, with the scale's resolution stated on the record.

Soot is a combustion product of incomplete burning, and the single biggest lever on it is wick length, which is why the index is only meaningful alongside the burn session procedure. A candle scored 8 with a trimmed wick and a candle scored 8 with an untrimmed one are not the same finding.

A soot index above 7 is flagged in orange wherever it appears on the site. That is not a judgement about the wax: it is a statement that the combination of wax, wick and fragrance load in that record produced visible deposition, and one of the three should change.

Soot card exposure烟灰卡暴露
Scale resolution天平分辨率
Photographs per record每记录照片数

Instruments used

  • Bench scale, 0.01 g resolutionOhaus CS3000
  • White collection card, 80 x 80 mm, matteno brand
  • Fixed lighting rig, 5000 K, 45 degreeno brand
  • Tweezers, stainless, flat tipno brand
  • Camera on a fixed tripod markfixed distance and exposure

Sampling table

Burns scored per record 8 to 10
Photographs per record 5
Weighings per record 2

Quantities produced

  • Soot index, 0-10blind photographic score
  • Consumption, g/hgravimetric over lit hours
  • Deposition flagraised above index 7

Environment: Same room as the burn sessions, 21-24 C, 40-55 %RH; photographs under fixed 5000 K lighting

Protocols cited

No published burn report cites this protocol yet.