At What Jar Diameter Should I Stop Assuming a Single Wick Is Best and Begin Comparing Single- and Double-Wick Configurations Experimentally?

Why the answer is an area, not a diameter

A wick's job is to melt a pool to the glass and keep it at a sensible depth. The pool is a disc, and a disc's area is π × r²: double the width and the area is four times as large. That is why "one wick works up to X cm" is misleading as a rule. From 7.5 to 10 cm inside the width grows by a third, but the pool grows 1.78 times. From CSI's 7 cm listings (about 6.3 cm inside) to a 7.5 cm inside jar, the pool is already 42% larger.

A pair doesn't halve the width a flame has to reach; it halves the area each flame has to feed, and it changes the shape of the job. Two wicks on a line reach the wall along that line quickly and the wall at right angles more slowly; one centred wick reaches every point of the wall at the same distance. So the per-wick area is a useful yardstick for "is a pair plausible here?", not a prediction of how the pair will burn. That caveat applies to every number on this page: it is geometry, and only a burn test turns it into an answer.

Pool area and area per wick, 6 to 12 cm

The last numeric column is the most useful. It translates "one wick of a pair in this jar" into "a single wick in a jar this wide". At 7.5 cm inside, each wick of a pair does the work of a single wick in a 5.3 cm jar, about the inside of CSI's 6 cm listings on our wall assumption. At 10 cm, each does the work of a single in a 7.1 cm jar, about the size of CSI's 7 cm listings read as the inside. So across the zone, a pair asks each wick to do roughly what single wicks do in the jars CSI's smaller rungs are commonly tested in. That is what makes the zone plausible for both configurations; it is not evidence that either will pass.

Why stop the table at 12 cm? Because past 10 cm the equivalent single for each wick of a pair keeps growing (to 8.5 cm at 12 cm inside), and the more useful question becomes whether three wicks share the pool better. That threshold is the three-wick threshold post, and the 2-versus-3 criteria for 11–12 cm jars are the two-or-three post.

The run-both zone, and why it starts at 7.5 cm

We start the zone where a pair stops being obviously too much. Below 7.5 cm inside, each wick of a pair would have less pool than a single wick has in the smallest jar CSI sells; you would be asking two flames to share a job one small flame commonly handles alone, and the tendency is a fast, deep, hot pool. So below the zone, the right test is single rungs: C1 against C2 in the smallest jars, as the 6–7 cm hub (the 6 cm catch-up post) and the 7.5–8 cm hub (the 7.5 cm catch-up post) do.

Inside the zone, both are plausible, and the evidence that picks one over the other is the burn: a thick ring around a well-melted centre leans toward a pair, a quiet flame with a shallow edge leans toward a larger single (the ring-reading tree is the 8.5 cm hub). The zone's job is only to stop you skipping one of the two arms.

The zone ends at 10 cm inside because by then a single wick is carrying a 78.54 cm² pool on one flame, and CSI's largest sized, tabbed single (Cotton Braided) is described only as for candles "exceeding 8 cm". Past 10 cm, start from a pair, and bring a third wick into the comparison when a pair leaves the edges behind; the 10–12 cm cluster starts at the 10 cm hub, and planning one, two or three wicks for a 4-inch luxury jar before ordering production quantities is the 4-inch jar post.

Where real jars fall

The jar in this cluster's title range, 8.5–9 cm, is your own: CSI doesn't list one. (One clip-top storage-style container is listed as "11cm * 11cm * 10cm" without saying which figure is the opening; measure it before placing it on the chart.) The Apothecary jar is the CSI listing inside the zone, but its page calls the glass "thick-walled", so our 0.35 cm wall may overstate its inside; measure it, and if it comes out nearer 9 cm inside it is still well within the zone. Its page also says "Safe for hot-pour up to 85°C", so with CSI 464, whose page states "Pour Temperature 80°C – 90°C", pour at 80–85°C: the lower limit governs.

What running both costs for one diameter

Two worked examples, both with Lemongrass and Lime at 8% on total weight in CSI 464, three candles on one Cotton Braided and three on two Eco C1: your own 9 cm jar at a 300 g fill, and CSI's Apothecary 500 gm at a 450 g fill (our labelled choice, leaving headspace under the page's "~500 g" capacity).

Two things stand out. The wick build barely moves the per-candle cost: a pair of C1 (₹11.80) is cheaper than one Cotton Braided (₹12.00). And the second arm is cheap next to the alternative: at 9 cm it is ₹880.33 of materials, while a 50-candle batch poured on a single that nobody compared with a pair is ₹14,682.12, about 17 times as much, before jars and labour.

Days: pour both arms the same day and they run in parallel, so running both adds candles, not time. In the 9 cm worked example: a week's cure (Lemongrass and Lime's page states no cure time in the text we captured; the 25 of 102 CSI oil pages that do say 48–72 hours for soy, and many makers wait about a week), burn 3 around day 10, halfway by weight around day 17, and about 1 cm left around day 21 at one 3–4 hour session a day. The 450 g Apothecary candles take longer; weigh them after every session rather than guessing.

Running both, side by side

The pass lines are the cluster's: a ring gone by burn 3 and never widening; at halfway, no flame leaning at the glass, no drifting wick, no soot band and a pool not running far past about 1 cm. The scorecard for reading those two points is the two-zone post; how far down a test must go before a configuration is commercially acceptable is the acceptance-gates post. Glass heat is judged by observation or a non-contact thermometer, never by touch.

What to buy, and what to skip

Five items for running both configurations in one diameter, chosen on page statements, price and stock on 29 September 2026. CSI publishes no wick-performance data, so nothing is ranked on burn results. Oil candles are counted at 24 g (300 g fill) and 12 g (150 g).

Frequently asked questions