What to Record in a Candle Burn Test Log

A good burn test log has two parts: the recipe details that let you repeat the candle, and the readings you take at each check. If someone else could pour the same candle and burn it the same way from your notes, the log is complete. The readings are flame height, melt pool, wick, jar heat, soot and scent.

What do I record about the candle itself?

Write these once per candle, before the first light:

• Date poured, and the date you started burning (so cure days are clear)
• Wax brand and type, and the lot or batch if you track it
• Fragrance oil and load, as a percent of wax
• Dye, if any
• Wick type and size
• Jar, and its inside width
• Room temperature. Armatage lists 68 to 86 degrees F (20 to 30 C) for the test room.

What do I record at each check?

Craftybase and Armatage list close to the same readings. Take them at the start, then about every hour, and again when you put the flame out:

• Time lit and time out
• Flame height. Armatage says to record it at least every 4 hours.
• Melt pool width and depth. CandleScience gives a depth target of about 1/4 to 3/4 inch (6 to 19 mm).
• Wick condition. Note mushrooming and carbon build-up. Armatage fails a candle with carbon balls bigger than 3/16 inch (5 mm), as its own check rather than an ASTM one.
• Jar heat. Craftybase and Armatage both use 140 degrees F (60 C) as a warning line, and Armatage says it is not an ASTM marker. More on that in our jar heat guide.
• Soot and smoke on the jar, the wick or in the air
• Hot throw, on a simple scale you keep the same every time, such as 1 to 5
• Leftover wax on the sides after the session, and any tunneling. CandleScience says to keep testing if the wax left on the sides is 1/8 inch (3 mm) or less after the first one or two cycles.
• Anything odd. Dripping, tipping, a cracked jar, a flame that went out.

What does a log entry look like?

Here is a made-up example for two test candles in the same jar and wax (all numbers are examples):

Reading it: candle A never reached the jar edge and left wax on the sides, which points to the wick being too small. Candle B reached the edge, had a flame near the 1 inch target, and stayed under 140 F. B is the one to carry into session 2. The log makes that call obvious, where memory would not.

Why bother writing it down?

Three reasons:

• Wax and oil change between batches. A log tells you whether a change in the candle came from the wick or from the new batch.
• A year from now you will not remember which wick went with which jar.
• If you sell wholesale, a shop or an insurer may ask what testing you did. Dated notes answer that.

Common mistakes

• Logging only the result (pass or fail) and not the reading.
• Changing two things at once, such as the wick and the oil load.
• A hot throw scale that drifts. Define 1 and 5 once and keep them.
• Forgetting the ambient room temperature. A cold garage and a warm kitchen are different tests.
• Recording the recipe in one place and the burn in another with no link between them.

Questions

How often should I take readings during a burn?

Check right after lighting and about every hour, per Armatage, and log flame height at least every 4 hours. For wick work, the 2-hour and 4-hour marks are the most useful.

Do I need to log jar temperature?

It is worth it for any glass or ceramic jar. A reading is far more useful than "it felt hot". Use an infrared thermometer on the outside of the jar at its hottest spot, which is my practice rather than a rule from a standard. Never touch a jar that may be hot to check it.

Can I use a spreadsheet?

Yes. A spreadsheet with one row per check works. The weak point is linking each row to the right recipe and wick, which is where most paper logs fall apart.