Signs Your Candle Wick Is Too Big

An over-wicked candle makes too much heat for its jar. The signs, from CandleScience, are a flame that is too tall and flickers, carbon "mushrooming" on the wick tip, wisps of soot, a hot container, and a melt pool deeper than 1/2 inch (13 mm). It can damage the surface under it and even crack the jar. If you see them, put the flame out safely, let the candle cool completely, and test the next size down. Never leave a candle burning out of sight, and test in your own jar with your own wax.

What are the signs?

CandleScience lists these for an over-wicked container candle:

• A tall, flickering flame. The flame "is too tall and flickers continually". Its target for a well-wicked candle is a steady flame about 1 inch (2.5 cm) tall.
• Mushrooming. The wick makes excess carbon that builds on the tip.
• Soot. Wisps of soot leave the flame now and then, and if the candle burns to the end the soot collects inside the jar.
• A very hot container. It "could damage the surface underneath or even crack".
• A deep melt pool. Deeper than 1/2 inch (13 mm), and the candle uses wax faster and burns for less time.

Craftybase's burn test guide lists signs of a wick that is too large: a flame taller than 3 inches (7.6 cm), carbon balls of 5 mm or more, and a container above 140 F (60 C). Armatage presents the 3 inch flame limit as part of the ASTM F2417 burn test. It lists the 5 mm carbon and 140 F lines too, but says they are not industry standard markers and that F2417-17 does not cover temperature or carbon. ASTM's public page for F2417-26 gives no test numbers, and the full standard is paid, so treat 5 mm and 140 F as maker rules of thumb.

What should I do right away?

If a candle is flaring, smoking heavily or the jar is getting hot to the touch, put it out. Armatage's checks for a fail include a cracked container, black smoke streaming from the wick, damage to the surface, or a candle that tips or spills. Do not touch a hot jar. Wait until it is cool before moving it.

How do I fix it?

First, trim the wick to 1/4 inch (6 mm) before every burn. CandleScience says a flame that is too tall means trimming before you light it. If the trouble stays, go down one wick size in the same series and retest. CandleScience notes that within one series a bigger number is a bigger wick, but numbers across series are not comparable. Also consider your fragrance load and dye: CandleScience says you can need a size down if you use less than 1 oz of oil per pound of wax (28 g per 454 g), a thin oil or no dye, and a size up when you use more.

Worked example: catching it by weight

An over-wicked candle burns wax faster. Weigh the candle before and after each session on a kitchen scale. This is my own habit and not a method from a standard. All numbers are examples.

• Candle A (wick size one down): starts at 24.0 oz, loses 1.0 oz in a 4-hour session. Rate: 1.0 / 4 = 0.25 oz an hour.
• Candle B (the size you started with): loses 1.3 oz in 4 hours. Rate: 1.3 / 4 = 0.325 oz an hour.

B burns 0.325 / 0.25 = 1.3 times as fast, 30 percent faster. If B's jar also peaked at 144 F (62 C) and A's at 128 F (53 C), the smaller wick is the first one to keep. If A then leaves wax on the sides, it may now be too small, and the answer is between the two sizes. Our guide on small wicks covers the other side.

Common mistakes

• Leaving the candle burning to see what happens.
• Fixing a hot jar by changing the label's burn time.
• Judging a wick before the candle has burned the 3 to 4 hours CandleScience suggests for the pool to form.
• Skipping the trim before every session.
• Changing the wick and the fragrance load together, so you cannot tell which did what.
• Comparing wick numbers between different series.

Questions

Is soot always a sign of a big wick?

No. CandleScience says soot can come from the wrong wick size, but also from poor wax, poor or excess fragrance, and too much fuel being drawn up the wick. Our soot guide goes through them.

Is a tall flame ever okay?

CandleScience's target for a container candle is about 1 inch (2.5 cm). Armatage quotes the ASTM F2417 limit as under 3 inches (7.6 cm), so a flame near or above that fails. I could not open the paid text of the standard, so check it before you rely on that number.

How many wick sizes should I test?

Two or three, side by side, with everything else the same. That way you can see the over-wicked one, the under-wicked one and the in-between.