My Double-Wick Candle Melts the Centre but Leaves Wax Along the Outside Edge — How Do I Know Whether Wick Spacing or Wick Size Is Responsible?

Why one candle cannot tell spacing from size

Think about where heat comes from in a double-wick pool. The strip between the two wicks is heated from both sides, so it melts first and melts deepest. That is why "the centre is fine" is the normal state of a double wick, not a clue. The outside edge is different: each patch of glass is served mainly by the nearer flame, from further away, and nothing heats it from behind. If a ring stays there, one of two things is true. Either each flame is big enough but sits too far from the glass, a spacing fault, or each flame sits in a sensible place but cannot throw heat far enough, a size fault.

From the finished candle, the two look alike. Both leave a band of solid wax around the outside after three hours; both leave the middle melted; both can look tidy on the flame. Makers usually guess. The wick-up guess is popular because it is easy, but a bigger pair in a spacing problem melts the centre deeper and hotter and still leaves wax at the part of the glass that is furthest away. The spread-them-out guess is popular with makers who have just read about spacing, but a small pair moved outward can leave the north and south edges further from any flame than before.

The ring's shape can give you a hint before you pour anything. A ring heaviest at 90° to the wick line leans towards geometry; a ring even all round leans towards power. Reading that shape on the candle you already have is the whole of the ring-shape map for a 10 cm pair. This page starts where the hint runs out: the test that settles it.

What 5 mm outward does to every distance

First, the jar. CSI lists no jar at 8.5 or 9 cm, so this is your jar, and its listing figure is probably the outside. Measure the inside at the rim, the middle and near the base. In the worked example we take a jar measured 8.5 cm outside with an assumed 0.35 cm wall, which gives 7.8 cm inside, a 47.78 cm² pool: 23.89 cm² per wick. Read 8.5 cm as the inside and you would overstate the pool by 19%. The mistake is not fatal, but it moves your marks.

Now put two wicks on a line through the centre, spacing s apart, in a jar of inside radius r. Three distances matter, and they are plain geometry, not burn predictions:

The wall along the wick line sits at r − s/2; the wall points at 90° to the line sit at √(r² + (s/2)²) from each wick. At spacing A the north and south glass is 1.74 times further from each flame than the east and west glass. Spread the wicks to B and the east and west gaps shrink by 0.5 cm, while the north and south distances grow by about 0.2 cm. The pool area per wick does not change at all: spacing redistributes the gaps, it does not add reach.

That is the logic of the whole test. If your edge wax is really a spacing fault, the cell at B on C1 should clear it, because the flames were big enough and just in the wrong place. If it is a size fault, only the C2 cells should clear it, because they reach further in every direction at once. A candle that needs both will clear only at B on C2. Spacing A and B are labelled starting points for testing: B is your current spacing plus 1.0 cm. If you already sit close to the glass, see the wall-gap trade for double wicks before moving outward at all.

The eight-candle 2×2

A 2×2 is the smallest design that separates two causes. Every cell changes at most one thing from its neighbours, and the A · C1 cell is your current candle, remade in the same pour so it acts as the control. Two candles per cell is the minimum that tells a real pattern from one odd wick; if the two candles in a cell disagree, that cell has not spoken yet.

The worked example is a 250 g fill at 8% of total weight: 20 g of Bergamot Amber and 230 g of CSI 464 per candle. Your fill is whatever you sell; keep it identical in all eight, because fill height changes how the pool develops. Bergamot Amber's page states "6-10% for soy wax candles"; 8% is mid-range. Do not move the load during this test. Load is a real lever, but it belongs in a separate round, and mixing it in here would give you a 2×2×2 with sixteen candles.

Why N, E, S and W and not just "some wax left"? Because the two levers act on those points differently. Moving outward shortens the gap to E and W and lengthens it to N and S; a bigger pair reaches further at all four at once. Geometry says N and S are the wall points furthest from any flame; heat says they are also the only wall points fed by both flames equally. Which effect wins depends on the candle, so log all four: a cell that clears E and W but leaves N and S has told you something different from a cell that clears everything. Four numbers per candle per session is 96 readings over the design, and it is those readings, not your impression, that you match to the patterns. The strip between the wicks is a different fault with its own test: the inward ladder for a strip between two wicks.

Five patterns, five verdicts

Pattern 1, spacing. B · C2 will often clear too; what matters is that B · C1 clears and A · C2 does not. The same small wicks, moved 5 mm out each, reach the glass. This is the best news: no new wick size, the cheapest candle (₹240.50 of oil, wax and wicks in the worked example), and flames that were already sized for the pool. Watch the new wick-line gap (1.9 cm in the example). Flames nearer the glass need the full life to show whether the glass gets too warm late on; judge that by observation, and with a non-contact thermometer if you own one (CSI does not list one). Never judge glass by touching it.

Pattern 2, size. Both C2 cells clear and B on C1 does not. The flames needed more reach, and moving small wicks did not supply it. Choose A · C2 over B · C2: both clear, and A keeps the flames further from the glass. It costs ₹7.08 more per candle in wicks than C1, which is ₹708.00 over 100 candles. Watch the centre on C2: a pair that clears the edge can make the middle deep and hot. That is the question the close-spacing ladder answers if it appears.

Pattern 3, both. Only B · C2 clears. You need more reach and wider placement at once, which is the build most likely to run warm near the bottom. Approve it only after both candles have burned to about 1 cm left with no flame lean, no soot on the glass and no heat observation you would not put your name to. If it fails late, the late-life double-wick retest in the double-wick candle that gets too hot near the bottom is the next step, not a bigger wick.

Pattern 4, nothing clears. A pair of CSI's sizes, at either spacing, does not reach the glass in this jar at this fill. Stop pouring and read the ring shape on the B · C2 candles: if the leftover wax sits mainly at north and south, two wicks on one line may simply be the wrong geometry for this width, and the three-wick threshold is the next read. Argued against our own interest: this is also the point where CSI's short wick range may be the limit. We have C1, C2 and Cotton Braided and nothing between; ask us on WhatsApp, and if another supplier's in-between size is what your jar needs, use it.

Pattern 5, everything clears. Your control cell, a remake of your own candle, clears too. The build was never the problem: the original ring came from how the candle was burned or made. The usual suspects are short sessions, a draught, a candle judged before cure, or a first burn that stopped early. Keep A · C1 and fix the habit. You have spent ₹1,992.34 to avoid changing a build that works, and that is money well spent.

Putting sixteen tabs exactly where you meant

A 5 mm test is only as good as a 1 mm mark. The design changes each wick's position by 5 mm. If your tabs wander by 3 mm in the pour, the test is measuring your hand, not your spacing. Three habits keep it honest: a template, a sticker under every tab, and a check after the wax has set.

Template. One card cut to the jar opening, used for all eight jars. Draw the centre and the wick line; mark A and B on both sides; punch through. Lay it in each jar, mark the base through the holes with a long pencil, and remove it.

Stickers. The Candle Wick Stickers page describes "10mm Candle Wick Round Stickers". Sixteen tabs use sixteen stickers from a 40-sheet (₹100.00), 24 spare. Press each tab down onto its mark and hold it for a few seconds.

Holding the tops. The Steel Wick Holder page says "3-hole layout fits single, double, or triple wick setups" and "up to 9 cm wide". It does not state the hole spacing, so measure it. Using the outer two holes gives you one fixed spacing: it may match A, B or neither. Where it doesn't match, rest a second card template across the rim, or tape two lolly sticks either side of each wick. A magnetic Wick Setting Tool (₹399.00) is sold for keeping a wick straight while the wax sets; its page describes nudging "the wick to the center", a single-wick job, so it is not the tool for a pair.

Check after setting. When the wax has set, measure each wick from the glass along the wick line at the surface. Write the four figures on the jar base. Any candle more than about 2 mm off its mark (our judgement) is re-poured before it is burned, because it would decide its cell on its own.

Grams, wicks and rupees for the 2×2

Buying from nothing: two 100 g Bergamot Amber (₹1,120.00), two 1 kg bags of CSI 464 (₹1,014.80), a C1 20-pack (₹118.00), a C2 10-pack (₹94.40) and a 40-sheet of stickers (₹100.00): ₹2,447.20. What is left: 40 g of oil (2 more candles), 160 g of wax, 12 C1, 2 C2 and 24 stickers. Your own jars are not in these figures; CSI's nearest wide listing, the Apothecary Glass Candle Jar with Dome Lid, is about 10 cm at the rim and base by its page, so it is not an 8.5 cm jar and would need its own test.

Per candle, in the worked example: a C1 pair build costs ₹240.50 and a C2 pair build ₹247.58, excluding your jar, labour, freight, packaging and GST. The whole difference between the builds is the wicks, ₹7.08 a candle. The difference between the spacing cells is nothing at all, which is why pattern 1 is the one to hope for.

Argued against our own interest: do not buy production quantities of either wick before the 2×2 reads. Per-wick price is flat at every pack size, so a 100-pack saves you nothing per wick over a 20-pack, and the 500 g of Bergamot Amber saves only ₹3.20 per candle over the 100 g (₹108.80 against ₹112.00). The test decides the wick; the price per wick won't.

What to buy, and what to skip

Skip for now: Cotton Braided Wicks Ready Made. Its page describes it for "large-diameter candles exceeding 8 cm", which makes it a single-wick candidate at this width, not an arm of a double-wick 2×2. If your 2×2 lands on pattern 4 and you want to know whether one big wick does better than a pair, that is the 8.5 cm head-to-head, and the general trade-off is single versus double in large jars. Also skip a trimmer (₹588.82) unless your scissors can't reach inside the jar: trimming matters, but it is not what decides this test.

Frequently asked questions