My Candle Jar Supplier Changed the Glass Slightly but Kept the Same Listed Capacity — Do I Need to Repeat Wick Testing?

Why "same capacity" doesn't mean "same wick"

A listed "150 g" is a fill figure, often approximate and sometimes to the brim rather than your fill line. The same volume fits in a slightly wider, shorter jar or a slightly narrower, taller one. Thicker glass shrinks the inside while the outside stays put. A new mould can round a shoulder, thicken a base or taper a wall, and still hold about 150 g. None of that shows on a listing. It shows in the melt pool. The pool's area grows with the square of the internal diameter, so small widths matter more than they look. Going from a 7.0 cm to a 7.2 cm internal diameter (a worked example) takes the pool area from 38.48 to 40.72 cm², 5.8% more surface for the same wick to melt. The arithmetic for 2, 3 and 5 mm steps is worked in the few-millimetres-wider post.

Most listings, ours included, don't help with this. Of CSI's 72 container listings, none states an internal diameter; the diameters given are outer, base or unspecified. The Clear Glass Jar with Golden Lid (150 gram) and the Black Glass Jar with Black Lid (150 gram) both state an outer rim of about 7 cm and a base of about 6.5 cm, but that tells you nothing about wall thickness or how either one compares with a delivery you already own. The external-versus-internal diameter post explains why the outer figure is the wrong one for wick choice.

A note on "supplier changed the glass". Mass-produced glass varies from batch to batch, and a supplier can change a mould or a factory without changing a listing. We are not saying any supplier, CSI included, has changed a jar. We are saying the only evidence that counts is a ruler and callipers on the jars in your hand. When the change is a spread within one delivery rather than old against new, see 3269. When you are choosing between two suppliers' near-identical jars before switching, the switching-suppliers checklist covers the up-front version of this sheet.

Burn changes after a jar switch: what points where

If you have already burned candles in the new jar, their behaviour points at which measurement moved. The ranking below, most common first, is editorial judgement; CSI has no failure data for jars. The rule-in and rule-out columns are measurements from the sheet in the next section.

Row 6 matters. If the sheet says the jars match, stop blaming the glass. The jar is often the thing that changed most visibly, but that doesn't make it the thing that changed the burn. Go back to the cluster hub's suspect ranking and look at your wax, wick and oil lots, or at a new wick carton.

The old-vs-new measurement sheet

Take three jars from the old stock (or from retained candles, if the stock is gone) and three from the new delivery. Label them O1–O3 and N1–N3. The sheet has eight rows. Measure each row on all six jars and write the mean for old and new, with the new-minus-old difference.

The retest rule: which difference triggers which test

Why an internal-diameter change always triggers a bracket, however small: we don't know your wick's margin, and neither do you until you test it. A wick that had room to spare survives a millimetre; one that was already marginal in the old jar doesn't. Four candles are cheaper than finding out from customers. If the fill line moved, the load percentage stays the same but the grams change. A 150 g candle at 8% is 12 g of oil and 138 g of wax; scale both to the new fill by weight. Net-quantity labelling falls under the Legal Metrology (Packaged Commodities) Rules; check current requirements. That is not legal advice.

The abbreviated bracket, costed

A full bracket tests three or more wicks from scratch. You don't need one, because the old jar already told you where the answer was. The abbreviated version keeps your current wick as one rung and adds the next step in the direction the diameter moved. The worked example: 150 g clear jars, CSI 464 at 8% (12 g of oil + 138 g of wax per candle), current wick C1, new jar wider, so the step is C2. In the 85°C-rated jar, pour CSI 464 at 80–85°C.

Costs are worked examples and exclude labour, freight, packaging and GST. One production candle in the worked example (Lavender at the 1 kg price, CSI 464, the clear jar and a C1) is ₹232.97 in materials, so a 500-candle run is ₹116,486.60; the bracket is 0.8% of that. How to read it: burn each candle in sessions long enough for a full pool (about 3–4 hours to the edge on the first burn is a common rule of thumb; about 2.8 hours by the rough one-hour-per-2.5 cm guide on a 7 cm jar), down to about 1 cm of wax left (common practice). Log pool, flame, soot and glass heat at the final third; the jar's heat is read with a non-contact thermometer, never by hand, and CSI doesn't list one. Current wick still reaches the edge, calm, through the final third: keep it and record the new jar in your spec. Only the step does: switch wick for the new jar; the C2 step costs ₹3.54 more a candle. Neither is right: run a full bracket (2726). For how far down a test burn has to go before you trust it, see the burn-depth post.

Jars, wicks and the scale

Four items: the two CSI 150 g jars whose listings state the same outer dimensions (a good illustration of why you measure), the wick rungs for the abbreviated bracket, and the scale for the fill line. They are chosen on page statements, price per unit and stock on 26 September 2026. No CSI listing states an internal diameter, so nothing is ranked on fit.

Frequently asked questions