I Changed from One Large Cotton Wick to Two Smaller Wicks in a Wide Jar — What Needs to Be Revalidated Besides Melt-Pool Width?

Two wicks change the geometry, not just the width

Makers usually move to two wicks for one reason: a wide jar that a single wick struggles to melt to the edge. Two smaller flames placed apart reach further along the line between them, so the pool gets to the glass at the wick ends much sooner. That is the melt-pool width the title mentions, and it is usually the first thing to improve. But the layout changes more than the width. The two flames sit closer to the glass on their own sides. Their heat meets over the centre of the pool. Each flame burns in the other's draught. The pool's weakest points move from "the whole rim" to two particular spots — the edge at right angles to the line between the wicks. And two wicks draw fuel at the same time, which changes how fast the candle is used up.

The geometry of spacing

Spacing is the one design decision two wicks add, and simple geometry shows the trade-off. This page uses an illustrative 10 cm internal-diameter jar — measure yours. With one centred wick, every point on the wall is 5.0 cm from the flame. With two wicks placed a distance s either side of the centre, the nearest wall is only R − s away from each wick, but the two points on the wall at right angles to the wick line are √(s² + R²) away from both — further than they were from a single centred wick. Those are the weak points: they depend on the two pools merging, not on either flame reaching them alone.

Read the columns together. Moving the wicks out from 2.0 to 3.0 cm brings each flame from 3.0 cm to 2.0 cm of the nearest glass — better for melting the wick ends, more heat on that glass. It also pushes the wicks 6.0 cm apart, so their pools have further to go to merge in the middle, and the weak points move from 5.39 cm to 5.83 cm away. Moving them in does the opposite: the flames stay away from the glass and merge easily over the centre, but the ends may not melt out. There is no published spacing rule for any CSI wick and jar. That is why the test runs two spacings side by side, chosen to bracket what you think is right.

Heat, draught and consumption

Three consequences of two flames deserve their own test lines. Heat near the glass: each flame is now closer to its side of the jar, so the hottest point on the glass moves to the spot nearest each wick. Take jar-side readings there, not only in the middle, and compare with the hottest point on the single-wick control. Heat in the middle: the two plumes rise over the centre of the pool and can make it run deeper there; measure depth at the centre and beside a wick. Draught: two flames close together can lean towards each other or flicker; note lean at 1 hour.

Consumption is the line makers most often forget. Two wicks draw fuel at the same time, and it is common for the candle to burn more grams per hour in total than with one wick — which shortens the candle's life and can make a burn-time claim untrue. Weigh every candle before and after every burn. The table below shows what a higher rate does to burn life, as pure arithmetic: the ratios are examples, not predictions of what your wicks will do.

CSI publishes no numeric jar-temperature or flame-height limit, and this page sets none. Acceptance for every heat line is no hotter than the hottest point on your approved single-wick control, and within your jar supplier's guidance and the candle fire-safety standard you work to. ASTM F2417 is a commonly cited US standard; if you follow it, use its methods. A stronger throw from two flames is only welcome if the heat lines pass — the better-throw, hotter-jar post explains why.

What to revalidate

Three NEW lines are the price of a layout change. The weak-point pool check did not exist with one wick. Wick spacing becomes a production tolerance — someone has to set two wicks at the right distance on every candle, and if they drift during the pour or the cure, the test result no longer applies. And customer instructions change: a two-wick candle lit on one wick behaves like a completely different candle, so the label has to say "light both wicks". The full wick-change checklist covers the lines shared with every wick change.

The nine-candle test

Scoring sheet

What two wicks cost per candle

At CSI's listed prices the wick choice changes the per-candle cost by only a few rupees on a 400 g candle — the oil and wax dominate. Here is the material cost of one illustrative 400 g candle at 8% with Bergamot Amber (1 kg rate, ₹5,437.00) and CSI 464 (10 kg rate, ₹5,074.00), excluding the jar, labour, packaging, freight and GST.

Two Eco Thin C1 wicks (₹11.80) cost slightly less than one Cotton Braided (₹12.00) and slightly more than one Eco Thick C2 (₹9.44). The real cost of a two-wick layout is elsewhere: setting two wicks at a fixed spacing on every candle takes more time, and if the candle burns faster, the customer gets fewer hours for the same price. CSI does not publish construction for any of these wicks and does not describe two Thin C1 as equivalent to one larger wick of any kind — the test decides.

The priced test kit

Nine illustrative 400 g candles in Luxury Soy Wax CSI 464 with Bergamot Amber Fragrance Oil at 8%, with a 5% pour-loss allowance (a labelled working assumption). The three controls use your existing large wick. Jars are not included: CSI does not list a double-wick or three-wick jar, and the White Matte Glass Jar and other CSI jars have no published diameter or fill weight — test in the wide jar you will actually sell. Use your own production wax and oil if they differ.

Bergamot Amber comes out as 3 × 100 g + 1 × 15 g (₹1,785.02) for 302.4 g; the oil is ₹5.60 a gram at both 50 g and 100 g, so the 100 g bottles simply mean fewer bottles. CSI also lists a Wick Centering Device (5 for ₹118.00) and Steel Wick Holders (5 for ₹250.00); check their product pages for two-wick use, or use any bar that holds both wicks at a fixed spacing while the wax sets. Labour, electricity and time are not included.

Deciding and releasing a two-wick layout

Record the result as a revised candle, not a wick swap: the jar, the wick, the number of wicks, the spacing and its tolerance, the test dates and the NEW lines. Add "light both wicks and trim both before each burn" to the label. Keep ten wicks and one finished candle from the first production batch as retained samples. If you are also changing the jar to a wider one, that is a second change — the wider-and-shorter jar post and the one-variable post explain why it is worth separating them.

Related wick changes: if the two smaller wicks give bigger individual flames than you expected, the bigger-flame post helps isolate why. If the pool reaches the wick ends but stops short at the sides, the gate-and-preference logic in the cleaner-but-smaller post applies, and the size-down post explains why early burns hide it. If you choose heavier wicks to close the weak points, run the lower-third checks in the one-size-up post, and if the wicks come with a different tab, see the tab-height post.

Frequently asked questions