I’m Using an 8.5 cm Jar with Soy Wax and One Cotton Wick — The Centre Melts Well but a Thick Wax Ring Remains; Should I Wick Up or Consider Double Wicking?

What a thick ring over a good centre is telling you

A tunnel in the usual sense is a small pool that sinks: too little heat everywhere. Your candle is different. The centre melts well, sometimes deeply, and the pool stops short of the glass, leaving a ring of solid wax several millimetres thick. That pattern says the flame has heat to spare near the wick and not enough reach at the wall. It is the pattern that sits on the line between single-wick and double-wick territory, which is why this cluster starts here.

Two forces decide how far a pool spreads: how much heat the flame puts into the wax, and how far that heat has to travel before the wax at the wall melts. In a small jar the distance is short and a modest flame covers it. At 7.8 cm inside, a centred wick has 3.9 cm to cover in every direction, and liquid wax near the flame carries heat down as well as out. A larger single flame commonly responds by melting both faster and deeper; whether it reaches the glass before the centre gets too deep is exactly what you don't know until you burn it. That is a tendency, not a rule, and it is why the answer is a test.

A pair changes the geometry rather than the size of the flame. Two wicks on a diameter at our starting spacing of 3.90 cm sit 1.95 cm from the wall along their own line. But look at the wall at right angles to that line: it is 4.36 cm from either wick, 12% further than a centred single wick is from any point on the glass. So a pair is not automatically better at reaching every edge. What it offers is more total flame spread over a longer line, and two smaller flames that each draw less fuel. Whether that closes your ring, or leaves crescents at the sides instead, is also something only a burn shows. Hold on to that picture: it explains most of the pair problems in posts 4244 to 4254.

Before any of that, rule out the two things that make a good wick look like a failing one. A short session: a very rough rule of thumb is about one hour of burning per 2.5 cm of width, about 3.1 hours at 7.8 cm inside; sessions of an hour or two in a jar this wide can't be judged on the ring. And a lopsided ring: 1 mm on one side and 9 mm on the other is a wick off centre, a draught, or a candle that set on a tilt, not a wick size. The tree below checks both first.

Your jar, measured from the inside

Let's be plain about the catalogue: CSI lists no 8.5 cm or 9 cm jar. None of its 72 container listings states an internal diameter, and none gives 8, 8.5 or 9 cm as a diameter or width. The nearest CSI figures are three 7.5 cm listings, all out of stock on 29 September 2026, the 7 cm listings (a single-wick question; start at the 7.5–8 cm hub) and the Apothecary Glass Candle Jar with Dome Lid, whose page gives an outer rim of about 10 cm, a height of about 10.8 cm and "Safe for hot-pour up to 85°C", in 500 gm (₹212.40) and 700 gm (₹250.00) sizes. That is a 10 cm question, covered from the 10 cm hub. For an 8.5 or 9 cm candle, the jar is yours, so the measuring is yours too.

Two things fall out of the table. First, reading the outside as the inside overstates an 8.5 cm pool by 19%: plan for the wrong jar and a wick that suits yours can look "too small". Second, 7.8 cm inside carries 24% more pool area than a 7 cm inside jar; a wick settled at 7 cm does not transfer. The full argument for inside diameters is the external-versus-internal diameter post.

The ring-to-configuration decision tree

The diagram above is the tree; this table is the same tree with its thresholds written out. Every threshold is our judgement, chosen because you can read it from a photo and a ruler: the practical flame range many makers use is about 2.5–5 cm, and the common pool-depth target is about 0.5–1 cm. Set your own standard if you prefer, then keep it fixed for every candle you compare.

What to log at burn 3

Before lighting: trim to about 5–6 mm, check the wick is central, and light in still air: no ceiling fan, AC vent or open window. At 2 and 3 hours: a photo from directly above with a ruler across the rim; the ring in millimetres at N, E, S and W; the trimmed flame height against a ruler held behind the jar, not touching it. At the end: pool depth at the centre and about 1 cm from the wall, with a skewer; any carbon cap on the wick; any dark film on the glass above the pool. Never judge the glass by touch. Keep burns 1 and 2 in the same log so you can see whether the ring is shrinking.

Notice what the tree never says: "your jar is 8.5 cm, so use two wicks". Diameter puts you in the zone where both configurations are worth testing; it doesn't pick one. Where that zone starts, by pool area, is the run-both-zone post, and the general trade-offs of a big single against two smaller wicks in any large jar are in the huge-single-wick-soot post.

Three arms, two candles each

Hold everything except the wick configuration: same wax bag, the same oil at 8% of total weight, the same jar batch, the same 250 g fill, pour temperature, cure and room. Three arms, two candles each, six candles: A, your current wick (C2 in the worked example; if yours came from another supplier, use it and tell us what it is); B, the larger single, one Cotton Braided; C, the pair, two Eco C1. Two candles per arm is the floor the tree needs to point a direction; a production decision needs the survivors carried to the end, and some makers pour three per arm from the start.

Why 2 × C1, not 2 × C2? Because the pair's usual failure in a jar this size is too much heat in the middle, not too little, and the smaller rung is the safer opening move (our judgement). If the pair arm leaves wax at the edges, 2 × C2 is round 2. Why Cotton Braided and nothing bigger? Because it is CSI's largest sized, tabbed wick. Its page describes it for candles "exceeding 8 cm", which puts 7.8 cm inside right at its stated edge: a fair rung for this test, not a promise.

Where the pair goes

Place the two wicks on the diameter line you marked, symmetric about the centre. Our starting point, labelled as such, is a spacing equal to the inside radius: 3.90 cm apart, which puts each wick 1.95 cm from the wall along their line. It gives each flame the same distance to the wall as to the midpoint between them. It is geometry, not a burn prediction; the detailed setup drawing for a 9 cm jar (4.15 cm apart and 2.075 cm to the wall on the same rule) is the 9 cm placement post. Hold the pair with the Steel Wick Holder only if its outer holes measure close to your chosen spacing; the page states no hole spacing, so check before you pour.

From nothing, the cash outlay is ₹2,061.34; if you already own the wax, oil and jars it is ₹582.40 for three wick packs and the holders. Per candle, excluding the jar, that is ₹223.57 on Cotton Braided, ₹223.37 on a pair of C1 and ₹221.01 on C2: ₹94.87 of oil, ₹116.70 of wax and the wick. The Cotton Braided candle costs ₹0.20 more than the paired one. At this scale the wick bill cannot decide the question; production labour for pairs can, and that is the scorecard post. Costs are worked examples and exclude labour, freight, packaging and GST.

Burn the arms in rotation in one still room, one session a day, each session about 3–4 hours or until the pool meets the glass. At a 3.1-hour rule of thumb for 7.8 cm, a two-hour session can't tell a ring that will close from one that won't; log the session length every time.

Reading the comparison

After burn 3, read each arm against the same questions as the tree: did the ring close, is the flame in range, is the centre deep, is there a carbon cap or soot? Treat an arm as passing burn 3 when both of its candles close the ring to 0–1 mm with a calm flame and no soot. A split (one passes, one doesn't) is undecided, not a pass: pour two more of that arm.

Burn 3 is where this hub stops. The candidates then need the full life to about 1 cm left, with depth, flame and the glass observed in the final third; pairs in particular commonly run warmer near the bottom, which is the subject of the double-wick-too-hot-near-the-bottom post. A pair that looks right at burn 3 and runs hot at the halfway mark is the two-zone scorecard.

What not to buy yet

And one purchase we'd steer you away from at CSI: a CSI jar to match yours. We don't list one at 8.5 or 9 cm, and the glass jars we do list at 6, 7 and about 10 cm would restart the question in a different geometry. If you want a CSI jar for a wide candle, the 10 cm Apothecary is a 10 cm question; if you want to decide one, two or three wicks before ordering jars at all, that is the 4-inch luxury jar post.

What to buy, and what to skip

Five items in the order the comparison needs them, chosen on page statements, price and stock on 29 September 2026. CSI publishes no wick-performance data, so nothing here is ranked on burn results. Oil candle counts use the 250 g worked-example fill (20 g each) and the standard 150 g candle (12 g each).

Map of this cluster: 4241–4260

This hub owns the short answer, the inside measurement, the decision tree and the three-arm comparison. Every other post in the cluster owns one test for one situation in an 8.5–9 cm jar where single and double wicks meet.

Coming from a smaller jar? The single-wick hubs are 6–7 cm and 7.5–8 cm. Going wider? The 10 cm hub starts where CSI does list a jar.

Frequently asked questions