I'm Changing to a Wider Candle Jar but Keeping the Same Soy Wax and Fragrance — How Much Should I Adjust My Starting Wick Size?

Size the step: pool area per centimetre

The wick melts a disc from its centre to the glass. That disc's area is π × r², with r half the inside diameter where the pool sits. So the thing to compare between your old and new jar is not the width, and certainly not the ml, but the area. The table shows what each extra centimetre of inside diameter does. Note the pattern: the area added grows with each centimetre, while the percentage falls, because you are adding to a bigger base.

Two practical readings. First, stepping up from a small jar is a bigger relative jump: going from 5 to 6 cm adds 44.0% to the pool, while 9 to 10 cm adds 23.5%. Second, half a centimetre matters: 7.0 to 7.5 cm is already 14.8% more pool, which is enough to move some set-ups by a rung. How much a 5 mm difference can do is worked through in the 5 mm post; the physics of why the wick follows the pool is in the tall-versus-wide explainer.

How to calculate your own step

Measure the inside diameter of both jars at pool height (1 cm below the fill line), using callipers, a steel ruler and card, or the water-rise check from the measurement hub. Then: area = 3.1416 × (diameter ÷ 2)². Divide new by old, subtract 1, multiply by 100. Or skip the π: (new diameter ÷ old diameter)² gives the same ratio. A 7.0 → 8.0 cm step is (8 ÷ 7)² = 1.31, so 30.6% more pool.

Four zones: where the bracket starts

Here is the step-up framework we would use. The percentages are our judgement, not industry data, and your wax and oil can push results a rung either way. That is why every zone still tests three rungs rather than jumping straight to one.

Two things the zones do not do. They do not tell you which wick wins, only which three to pour. And they do not replace the full burn-down: a wick that makes a perfect pool at the top of a wider jar still has to be watched in the final third, especially in heavier glass. Whether a wide jar should run one wick, two or three is its own decision in the 4-inch luxury jar post and the single-versus-double post.

CSI's wick ladder, and why its steps are coarse

"One size up" only means something on a particular ladder. On CSI's catalogue the cotton ladder is short: Eco C1, Eco C2, then Cotton Braided Wicks Ready Made (one size), then doubles. Performance Wooden Wicks sit to one side as a different family with no size options listed. So a step-up bracket on CSI wicks looks like this:

Because the steps are coarse, a Zone 1 or small Zone 2 jump can land between rungs: the current wick slightly under-melts and one up slightly over-melts. When that happens, look at the variables you are allowed to change without breaking the "same wax, same oil" premise: wick trim length (a common working length is around 0.5 to 0.6 cm, rule of thumb), wick centring, and the first burn's duration. Load changes are a last resort, and a separate test; the fragrance-load post explains how load can move a wick.

Two steps inside CSI's own jar range

To make the zones concrete, here are two moves a CSI customer could make. Inside diameters are worked-example assumptions from the listed outside figures, because no CSI listing states an inside diameter.

Step A is the textbook case. A 41.3% jump sits in Zone 2, so your C1 becomes the low rung, C2 the middle and Cotton Braided the top. Nine candles and an afternoon of burning will tell you whether C2 is right.

Step B is not really a step. More than double the pool, a thick-walled jar and a candle more than three times the weight. Your C1 is off the bracket entirely; the bracket starts at Cotton Braided and includes two doubles, and at that point the question is no longer "how much do I adjust" but "how many wicks does this jar want", which is the one-two-or-three-wicks post. The Apothecary page gives one set of dimensions for both its 500 gm and 700 gm sizes, so measure the inside before trusting any number here.

A third move shows the opposite. The Green Iridescent jar lists "Diameter - 7cm" and "Capacity - 300g", taller than the Matte family's 8 × 7 cm. Moving from one to the other is a step in capacity, not necessarily in width. If the insides measure alike, you may be in Zone 1 or no zone at all: same bracket, longer burn-down. Height adds sessions, not wick size.

The step-up test, with a control candle

A step-up test has one extra element a first bracket does not: a control. Pour one candle in your old jar with your old, proven wick from the same pitcher. If the control behaves as it always has, any change in the new jars is the jar's doing. If the control misbehaves too, your wax lot, oil lot or cure changed, and you have saved yourself from blaming the wick. (Which parts of a previous test you can skip when only the width changes is a separate scope question, taken up in the retest-scope post.)

What to buy for a step-up bracket

Five items, chosen on page wording, price and stock on 26 September 2026. CSI has no burn data for any of them in your jars.

Costed: a small step and a big one

Prices are CSI live pricing on 26 September 2026; all loads are 8% on total candle weight, inside both CSI 464's stated 10% and the Jasmine page's "Recommended load up to 10% soy"; costs exclude labour, freight, packaging and GST. Jasmine is the costing example; use your own oil.

With your own jars, step A costs ₹1,700.80. The control candle is a 120 g Shiny candle at 8% (9.6 g oil + 110.4 g wax) in a jar you already own.

Step B costs 1.8 times step A for fewer candles, because each test candle is a 500 g candle in a ₹212.40 jar. One finished step-B candle with two C2s is ₹212.40 + ₹233.40 of wax + ₹156.92 of Jasmine at the 1 kg price + ₹18.88 of wicks = ₹621.60 in materials; a single Cotton Braided instead of two C2s would cost ₹6.88 less per candle. Neither wick figure matters next to the jar, wax and oil in a failed 500 g candle. That is the argument for a proper bracket on a big step.

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