My New Wick Has a Different Tab Height and the Flame Extinguishes with More Wax Remaining at the Bottom — Could the Tab Change Usable Candle Life?

Yes — the neck sets where the candle ends

The metal tab at the base of the wick has a crimped collar — the neck — that grips the wick. Below the top of that neck, the wick cannot draw molten wax up to the flame, so once the pool drops to that level the flame starves and goes out. Change the neck height and you change the level at which the candle ends. A taller neck stops the flame higher and leaves more wax behind. That is general candle-making knowledge, commonly described, not a CSI measurement — CSI does not publish tab heights for any of its wicks. But it means your observation has a straightforward mechanism, and the answer to the title is yes: a tab change can change usable candle life, and you can measure by how much.

Two other things can add to the leftover as well: wax left on the walls if the late burns tunnel slightly, and wax the flame never reaches because the wick has leaned. So the neck is not the only suspect, and a weighed test is better than a ruler. The tab-change post covers what else a tab change can alter at the end of a candle — extinction, tab lifting, heat at the base. This page does the arithmetic: how many grams, how many hours, how many rupees, and what to do about it.

From millimetres to grams: the geometry

You can predict the size of the effect before you burn anything. The leftover layer is roughly a disc of wax the width of the jar's inside and as thick as the difference in neck height. Area is π × d² ÷ 4 and volume is area × height, so in an illustrative jar with a 7.6 cm internal diameter — not a published figure for any CSI jar; measure yours — each millimetre of extra height is 45.36 cm² × 0.1 cm = 4.54 cm³. Solid wax is lighter than water; using a labelled approximation of 0.86–0.90 g per cm³, that is about 3.9–4.1 g of wax per millimetre, or 1.95–2.04% of a 200 g candle. The conversion varies by wax and temperature, and is not a CSI specification — your weighed test replaces it.

Measure the neck heights of ten old and ten new tabs with callipers and take the difference of the averages. If it is 3 mm — the example used on this page — expect roughly 11.7–12.2 g more wax left in every candle. That is before wall hang-up or a leaning wick, which is why the test weighs the real leftover rather than trusting the geometry alone. If the jar tapers towards the base, use the internal diameter at the bottom, not at the rim; the post on jars that narrow towards the bottom explains why the base diameter behaves differently.

From grams to hours and rupees

Grams become hours through your consumption rate — the grams a candle loses per hour of burning, which you measure by weighing before and after each burn. The table shows the arithmetic with example rates that you replace. At an example 5 g per hour, 11.7–12.2 g of extra leftover is about 2.3–2.4 fewer hours of candle — more than half of a typical 4-hour session.

The rupees are smaller per candle but add up. The leftover is candle, not just wax, so it holds 8% oil as well. With Mango Coconut at ₹3.96 a gram (1 kg rate, one of the oils with a real bulk step — it is ₹5.00 a gram at 100 g) and Luxury Soy Wax Chunks at ₹599.00 a kilo, 11.7–12.2 g of leftover is ₹10.16–₹10.63 of material per candle that the customer cannot use — ₹10,161.47–₹10,634.10 over 1,000 candles. You still paid for it; the customer still carried it home.

The same money logic applies whichever way the tab moved. If the new tab came with a lower price, the extra leftover belongs in the payback sum in the ₹2-per-candle post: a wick that saves a rupee or two and leaves ten rupees of candle in every jar is not cheaper. And if you already hold thousands of the new-tab wicks, the 5,000-wick post covers what to do with them.

What the tab-height change invalidates

The weighed leftover test

The test is a full-life side-by-side with one addition: every jar is weighed empty, with its wick and sticker, before it is poured. That tare weight is what turns the final weight into a leftover in grams. Three candles per tab is the series' labelled working minimum; one retained control completes the set.

The decision rule — and the options

The last option needs a caution. It is tempting to see a taller neck as waste and a shorter one as value, but the neck height the old wick shipped with may have been chosen to keep the final flame a safe distance from the glass base. CSI publishes no numeric base-temperature or flame-height limit, and we will not suggest one; the line is "no worse than the approved tab", your jar supplier's guidance and the fire-safety standard you work to. A hotter last burn is never traded for more usable wax — the same rule the hotter-jar post applies to throw.

The priced test kit

All items are listed, in-stock CSI sizes on the pull dates, with a 5% pour-loss allowance (working assumption). The wicks are yours — old-tab and new-tab — so they are not priced. Luxury Soy Wax Chunks are rated up to 13% fragrance load by the wax maker, so 8% is inside the stated maximum. The White Matte Glass Jar's internal diameter and fill weight are not published; measure the one and weigh the other.

Release and record

If the tab changed and you have not yet seen any difference, start with the tab-change post, which sets out the full end-of-life check. If the new wick also ends earlier because it struggles half-way down, the smaller-flame post covers pool width through the full life, and the thicker-base jar post covers the same end-of-life questions when the jar, not the wick, changes.

Frequently asked questions