Two Glass Jars Have the Same Capacity but Different Diameters — Can I Use the Same Wick If the Wax and Fragrance Stay Identical?

Why capacity cannot carry a wick from one jar to another

Capacity is the inside area of the jar multiplied by its height, give or take a shoulder. The same 130 g can sit in a narrow, tall jar or a wide, short one; the label cannot tell you which. The flame, meanwhile, only ever deals with the top surface of the wax: it has to melt a pool from the wick out to the glass, all the way round, in the first few hours of burning. That pool is set by the inside diameter, and the capacity does not appear in it at all. The full physics of why narrow and wide jars burn differently with the same wax is in the tall-narrow vs short-wide post; here we only need the conclusion: the wick follows the diameter, not the ml or grams.

What capacity does change, when the diameter changes with it, is how deep the wax column is. The narrow 130 g jar holds its wax in a taller column, about 1.65 times deeper than the wide one on our wall assumption, so it burns for more sessions, and the flame spends longer lower in the glass, where heat tends to build. That is a second reason the same wick can behave differently in the two jars even if both pass the first burn.

"Identical wax and fragrance" is necessary, not sufficient

Keeping the wax, oil and load identical removes the other reasons a wick result can move. That matters: without it you could not tell a jar effect from an oil effect. But it does not make the jars identical. With everything else held still, the only thing left to change the result is the geometry, and the geometry is exactly what differs.

Worked area difference: same-capacity pairs from CSI's own listings

CSI's listings include pairs of containers that state the same capacity and different diameters. None of the pages says whether the diameter is inside or outside, so we show both readings: the listed figure as written, and the listed figure minus two walls of about 3.5 mm (the illustrative wall used across this series; ceramic walls may well be thicker). Pool area is π × r² on the radius.

Read the percentages, not just the areas. On the listed figures the 120 g pair differs by 44.0% and the 130 g pair by 56.2%. Subtract the walls and the gaps grow, to 51.9% and 64.6%, because the same wall thickness is a bigger share of a narrow jar than of a wide one. That is a general point worth keeping: comparing outside figures understates how different two insides are. How an external figure misleads a wick choice is the external-vs-internal post.

Read the reach, too. In the 130 g pair the flame in the wider jar has to melt 3.4 cm from wick to glass instead of 2.65 cm, 28% further in every direction. No single wick is likely to be right at both distances; the burn test is how you find out whether one is close enough.

The 200 ml pair is the one you are most likely to face with our range

Both 200 ml jars are in stock, both are sold as 200 ml, and one page gives no diameter at all. The Matte family's "width 7 cm" may be outside (6.3 cm inside on our wall assumption); the Salsa page states only a 63 mm lug cap and a "Wide Mouth Opening", and a threaded neck usually sits above a wider body. So the Salsa's inside at pool height could be narrower or wider than the Matte's. Worked example: if it measured 7.0 cm inside, it would have 23.5% more pool than a 6.3 cm Matte; if 5.8 cm, 15.2% less. Either is enough to move a wick. Why two "200" jars can hold different weights is covered for fill in the same-ml, different-shape post; this post is about the wick.

Predict before you burn: which way will the new jar fail?

Before you pour, work out which direction the new jar should go wrong, so the burn test has a question to answer.

How much difference is too much to carry a wick across is a tolerance question that belongs to the standardising post, and what a single 5 mm step does to pool area is the 5 mm post. The honest summary for this post: you do not need a tolerance figure to decide whether to test. If two jars are not the same jar, test.

How to measure both jars the same way

Callipers across the inside 1 to 2 cm below your fill line, read at right angles; again near the base; and the wall thickness at the lip. Water-fill both to your fill line on a scale, because a different diameter at the same capacity also means a different fill height, and the fill line sets how many burns the candle has. Record the lot on the same sheet as the proven jar's figures.

How to prove the same wick works: the control-and-neighbour test

The test has three groups. A control: one candle in the jar the wick already passes in, poured from the same batch, so you can see whether today's wax, oil, room and cure are behaving normally. The claim: three candles in the new jar on the same wick. The fallback: two candles in the new jar on the neighbour your prediction pointed to. Worked example: C2 proven in the 200 ml Matte jar, switching to the 200ml Salsa jar, 150 g candles at 8% (12 g oil + 138 g wax) in Luxury Soy Wax Chunks with British Rose. Weigh your own fills first.

What to buy to prove it

Five items: the new jar in the worked example, the two same-capacity jars from our pairs that are in stock, the two wick rungs, and the wax. Chosen on page wording, price and stock on 26 September 2026.

The money: proof against a 100-candle switch

Worked example: switching a 150 g candle at 8% from the 200 ml Matte jar to the 200ml Salsa jar. The saving is real: ₹70.80 per Matte jar against ₹29.50 per Salsa jar at 100 Pcs, so 100 jars cost ₹4,130.00 less. Prices are CSI live pricing on 26 September 2026; costs exclude labour, freight, packaging and GST.

The C1 pack assumes the Salsa jar measures narrower than the Matte, so C1 is the neighbour; if it measures wider, swap it for ten Cotton Braided (₹120.00) and the kit is ₹1,356.20. If you already hold both wick sizes, the proof is ₹1,141.80. British Rose is our example because its page states candles "up to 10% soy" and every size is in stock; it is ₹3.42 per gram at 100 g and ₹3.07 at 1 kg. Use the oil the wick was proven with, or the proof proves nothing.

What the proof protects

The proof is 7.4% of that order, and 31% of the jar saving the switch was meant to deliver. If the same wick fails in the Salsa jar, finding out on five jars costs ₹200.60 in glass; finding out on a hundred costs the hundred candles, the time to melt out and re-wick them, and the customers who burned them first.

Frequently asked questions