How to Choose the Right Candle Wick Size

Pick a starting wick from your supplier's chart using your wax and your jar's diameter, then test it. No chart can know your exact fragrance, dye and jar, so the burn test makes the final call. A wick that is too big can overheat the jar, so test in your own jar with your own wax and oil before you sell anything.

What are the steps to choose a wick?

This is the order I follow for every new jar or wax.

1. Measure the jar. Measure the inside width of the jar at the top, across the wax surface. The melt pool has to reach that width, so that is the number the chart wants.
2. Look up a starting size. Open your wick supplier's chart (CandleScience calls theirs the Wick Guide), find your wax, and read the size where it meets your diameter. CandleScience says to use the guide "as a starting point to conduct your own testing."
3. Adjust for fragrance and dye. CandleScience says to go up one or two sizes if you use more than 1 oz of oil per pound of wax (28 g per 454 g), a dense oil or a lot of dye. Go down one or two if you use less than that, a thin oil or no dye.
4. Pour two or three test candles. Same jar, same wax, same oil, same dye. Change only the wick, and keep to one series. CandleScience warns that jumping between series gives confusing results.
5. Wait, then burn them together. Label each jar with its wick. CandleScience says to wait at least 24 hours before testing, and to burn all candles at the same time so you can compare them.
6. Judge each one. Check the flame, the melt pool, the wick and the jar. The targets are below.
7. Move one size and retest. Under-wicked means go up one size. Over-wicked means go down one. Retest when you change the wax batch, the oil or the dye.

What should a good burn look like?

CandleScience gives these targets for a container candle:

• Flame about 1 inch (2.5 cm) tall and steady, not flickering a lot
• Melt pool reaching edge to edge, about 1/4 to 3/4 inch (6 to 19 mm) deep
• Clean burn with little smoke or soot, and clean jar sides after a full burn

If the pool has not reached the edge, one of their guides says to let the candle burn 3 to 4 hours at one lighting before judging. In another, the check point is about 2 hours and the depth target is about 1/2 inch (13 mm). Different suppliers use slightly different checkpoints, so pick one and use it every time. Our burn test guide shows the full method.

How do I know the wick is wrong?

• Too small: the pool will not reach the edge, and the candle tunnels down the middle. The flame may go out before the wax is used up.
• Too big: a tall, flickering flame, a pool deeper than about 1/2 inch, soot, and a jar that gets very hot. CandleScience says an over-wicked container can crack.

Worked example: fragrance load and the 1 oz rule

Say your recipe uses 8 percent oil and a candle holds 12 oz (340 g) of wax. All numbers here are examples.

• 12 oz of wax is 0.75 lb
• Oil: 12 x 0.08 = 0.96 oz
• Oil per pound: 0.96 / 0.75 = 1.28 oz per lb

That is above 1 oz per pound (6.25 percent), so the supplier note says to consider testing one size up from the chart. Test it next to the chart size, because the chart may already be right.

Common mistakes

• Choosing by jar volume or height. Width is what matters.
• Trusting the chart and skipping the test.
• Comparing numbers across series. Within a series a bigger number is usually a bigger wick, but CandleScience notes that numbers between series are not comparable: an LX 22 may or may not be bigger than an ECO 8.
• Testing a wick that is too long or too short. Trim to about 1/4 inch (6 mm) before every burn, as the Makesy guide says.
• Buying wicks with no word on lead. In the US, candles with metal-cored wicks made or imported on or after October 15, 2003 must have a metal core with no more than 0.06 percent lead (16 CFR 1500.17(a)(13)). Buy from a supplier that says its wicks conform.

Questions

Should I measure the inside or outside of the jar?

Measure the inside, across the open top where the wax sits. The melt pool grows until it hits the inner wall, so the inside width is the one that sets how much heat the wick must make. This is my practice rather than a rule from a standard.

How many wick sizes should I test?

Makesy says to burn-test at least three wick sizes in your vessel before a production run. CandleScience says two or three. Three gives you one on each side of your best guess.

Do wide jars need more than one wick?

Often, yes. Makesy suggests a double or triple wick setup for vessels 4 inches (10 cm) wide and larger, and says vessels over 3.5 inches (9 cm) may need a larger series or multiple wicks. Test it like any other.