My Candle Has a Good Melt Pool for the First Few Burns but Becomes Extremely Deep Near the Bottom — Does This Mean I’m Over-Wicked?

What a deep pool near the bottom can mean

A melt pool about 0.5–1 cm deep is the commonly cited target for a container candle (a rule of thumb, not a CSI figure). It is a useful number because it balances two things: enough liquid wax to feed the wick and release fragrance, not so much that the wick has more fuel than it can burn cleanly. Past that, a pool is described as "deep", and a deep pool commonly travels with a taller flame, more carbon, and more heat going into the glass. That is why a deep pool near the bottom worries people, and it should: the lower section is where heat already builds.

Why would the same wick melt deeper lower down? Once the flame is below the rim, the glass above it shelters it and absorbs heat; after hours of cumulative burning the jar and the wax beneath the pool are warmer than they were on day one. A pool sitting on warm wax, inside warm glass, tends to melt further down in the same session. In a jar that narrows toward the base, the same heat also goes into a smaller area. None of that is a fault. It is the reason a wick is judged by the whole jar, and the reason "a good pool for the first few burns" is where the test starts, not where it ends (the three-stage map).

But depth has two other causes that have nothing to do with a big wick. A pool that never reached the wall concentrates the heat in a narrow column, so it goes down instead of out: that is tunnelling, and it is under-wicking. And a pool read after a four- or five-hour session is deeper than one read after three, whatever the wick. The first sends you to a bigger wick, the second to a shorter session. Get the reading wrong and you buy the opposite of what the candle needs.

Deep-pool patterns: which ones say over-wicked

The order below is editorial judgement, most common first; CSI publishes no failure statistics and no measured burn data. The last two columns carry the weight: what would rule each cause in, and what would rule it out.

Patterns 1 and 4 are habits: fix them first (fixed session, fixed trim) and chart again, or the chart will measure your habits. Pattern 3 is the one that most often gets misread; it needs the tunnelling route, not this page. Pattern 5 overlaps with the stop line; if the rise only begins below where you should stop anyway, keep the wick and move the stop line up (thick bases near the bottom). Pattern 6 is geometry, profiled in the diameter-at-height post. Pattern 2 is the question in the title, and the chart below is how you show it.

The depth-and-diameter chart, burn by burn

The chart plots two readings against one axis. The axis is wax remaining above the inside base, because depth problems are about where in the jar the pool is, not which burn it is. The readings are pool depth and whether the pool reached the wall. Session length and trim are held fixed so they can't move the line. Chart the problem candle's twins, not the problem candle itself, if you can; they start from the top, where the baseline comes from.

In the worked example, candle A averages 0.80 cm across its top-half burns and 1.55 cm across its lower-half burns, with the pool at the wall every time; the halfway line sits at 3.0 cm of a 6 cm column. Those are illustrative readings chosen to show the shape; your own candle's numbers, column height and session length will differ. What matters is the shape, and that it was drawn under fixed conditions.

Reading the chart: the lower-half rule

The rule this page owns is short: if the pool was on target (about 0.5–1 cm) and at the wall through the top half, and goes past about 1 cm only in the lower half, still at the wall, at fixed session length and trim, the wick is over-sized for the lower section. The top half does the work of a control candle: same wax, oil, wick, jar, pour, room and routine, differing only in where in the jar it is burning. The table sets out the other shapes the chart can take.

Two limits on the rule. The 1 cm line is a commonly cited rule of thumb; some makers work to a slightly different figure, and what matters most is a clear change between the halves. And depth is one reading among several. A lower half that is deep but calm, clean and cool on a non-contact thermometer is a milder finding than one that is deep with a tall flame, soot and a hot jar; the second is the final-third safety question, not just a depth one.

Confirming with one step down

If the chart meets the lower-half rule, the prediction is that one wick step down will keep the lower half near the band while still reaching the wall in the top half. Test that prediction the same way: a pair of candles on the smaller wick, charted under the same fixed conditions, to the stop line. In the worked example that is Eco C1 in place of C2 in the 150 g jar, with CSI 464 and Gardenia at 8% of total weight (12 g of oil and 138 g of wax per candle), poured at 80–85°C (the jar page's 85°C governs). The pair takes 24 g of oil and 276 g of wax.

Costs are worked examples and exclude labour, freight, packaging and GST. If you already own the wax and jars, the new cash is ₹282.02 (the oil and ten C1); from nothing it is ₹1,733.42. If you have no unburned twins of the problem candle to chart, pour a pair on your current wick at the same time (₹454.77 in materials with C2); both pairs together come to ₹902.46, and the 50 g of Gardenia covers all four candles with 2 g to spare. In your own production oil the answer is about your candle rather than ours.

Read the pair with two gates. The top half: does the smaller wick still reach the wall within your first-pool limit? The lower half: does its depth stay near the band to the stop line, and does it pass every final-third safety check (the hot-jar post)? Both yes: adopt it. Lower half fine but top short of the wall: neither wick size works alone, and the options beyond size take over. Neither: chart again with a third candle before deciding.

What not to buy for a deep pool

A deep pool invites the wrong purchase more readily than most symptoms, because it can point either way. We would rather you charted first, even though that delays a sale.

What each chart shape does need is short. Over-wicked for the lower section: ten C1 and a charted pair. Whole-jar over-wicking: a bracket from the top. Tunnelling: the other direction. Base zone: a higher stop line. No depth problem at fixed sessions: a care line about session length and trimming.

Four items for the chart and the step down

Four items: the wick step the lower-half rule points to, the tool that keeps wick length out of the chart, and the oil and jar in the worked example. Chosen on page statements, per-unit price and stock on 26 September 2026; CSI has no measured burn data, so nothing is ranked on performance. The oil table shows every size, candles at 12 g, and chart pairs at 24 g.

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