I Moved One Wick Size Up Because My Normal Size Was Unavailable — What Should I Check Before Producing Hundreds of Candles?

What moving one size up can change

When the usual wick is unavailable, going one size up feels like the cautious choice: the candle will certainly reach the edge, tunnelling is unlikely, and the first burn usually looks excellent. That is exactly why it needs care. A heavier wick in the same candle generally delivers more fuel to the flame, and the extra heat does not show evenly across the candle's life. In the top third, there is plenty of wax to absorb it and the glass starts cold. By the lower third, there is less wax, the glass has been warmed by every previous burn, and the flame sits closer to the base of the jar. If an up-size is going to cause a problem, that is where it usually shows.

A size label within one supplier's series is also less precise than it looks. Steps between sizes are that maker's choice and are not the same across series or suppliers; CSI does not publish construction or a step size for its Eco Candle Wicks, and the Thin C1 and Thick C2 names describe two listings, not a measured increment. So treat "one size up" as a new wick with a known direction, not a known amount. Here is what it can change, and where in the candle each change tends to appear.

Why the lower third matters most

Three things combine as a container candle burns down. First, there is less wax around the flame, so the same heat raises the pool temperature more. Second, the glass has been warmed repeatedly and the flame is now inside the jar rather than near its rim, so more heat goes into the sides. Third, the pool sits closer to the base, and if the pool is deep, the flame can end up close to the tab and the bottom of the jar. None of these is a problem in a well-matched candle. With a wick that runs hotter than the one the candle was designed around, they add up — which is why jar-side heat and pool depth need extra readings in the last burns.

CSI publishes no numeric jar-temperature or flame-height limit, and this page does not supply one. What you can do is measure the same way at the same spot every time — a pen thermometer against the outside of the glass about a third of the way down from the current wax surface, or a consistent touch check if you have no thermometer — and compare the up-size with your normal wick at the same stage. No hotter than the control, and within your jar supplier's guidance and the candle fire-safety standard you work to, is the acceptance. ASTM F2417 is a commonly cited US standard; use its methods if you follow it.

What to retest

The NEW line is not a laboratory test; it is a production control. Because you are about to make hundreds of candles on a substituted wick, pull a few from the first production batch and burn them before the batch ships. Test candles are poured with care; production candles show whether the wick behaves the same in ordinary hands and at production speed. The decision section sets out a simple hold-and-release routine.

The six-candle full-life test

Your burn-time claim and your cost per candle

If your label or listing states a burn time, it rests on the old wick's consumption rate. An up-size commonly burns faster. The arithmetic is simple: hours ≈ wax burned ÷ grams per hour. Suppose your label says about 40 hours for a 200 g candle — an example figure; use your own claim. That implies an average of 5.0 g/h across the candle. The table below converts other consumption rates into hours. These rates are arithmetic examples, not predictions of what any wick will do; replace them with the g/h you measure.

The wick itself also costs more per candle in many series. On CSI's listed prices an Eco Thin C1 is ₹5.90 and an Eco Thick C2 is ₹9.44 — ₹3.54 more per candle. Across a production run that becomes real money, and it is worth knowing before you decide to stay on the up-size after your normal wick is back.

If the up-size passes every line, the extra rupees may be well spent to keep production moving. If it passes only because you have not yet burned to the end, they are the smallest part of what it could cost you. The ₹2-per-candle post shows how to weigh a wick's price difference against the testing it needs.

Scoring sheet with heat by third

Deciding, and holding the first batch

For the first production batch on the up-size, a simple hold works well. As an example — replace with your own numbers — on a batch of 300, pull 3 candles at random after curing, and burn them through at least three cycles alongside a control before the batch ships. If they match the test candles, release. If not, you have caught it with 300 candles on the shelf rather than in customers' homes. Record the batch date, the wick order date and the pull results.

The priced test kit

Six 200 g candles in Luxury Soy Wax Chunks with Apple Cinnamon Fragrance Oil at 8%, with a 5% pour-loss allowance (a labelled working assumption). The control candles use your remaining normal wicks. Use your own production wax and oil if they differ.

Apple Cinnamon is ₹4.74 a gram at 50 g, 100 g, 500 g and 1 kg alike — one of the oils with no per-gram break above 50 g — so for the test, 100 g + 15 g (₹567.58) is simply the tightest fit. Labour, electricity and time are not included; cost them from your own figures.

Recording a temporary substitution

Most up-sizes made during a stock-out are meant to be temporary. Record them that way, so the candle does not drift permanently onto a wick nobody formally chose. Write the change record with: the normal wick, the substitute, the reason (stock-out, with date), the test dates and results, which SKUs and batches used the substitute, and a planned review date — for example, "return to normal wick when back in stock; if staying, re-approve". Mark each production batch made on the substitute so a later complaint can be traced to it. The change-control form post has a template, and the emergency 1,000-candle post covers the absolute minimum when there is no time for a full-life test.

Related wick changes: if the up-size also gives a visibly bigger flame from the first burn, the bigger-flame post has an isolation test that separates wick from trim. If the heavier wick arrives with a different tab, the end-of-life checks in the tab-height post apply as well. The storage-testing post explains why an up-size rarely needs new storage tests, and the full wick-change checklist lists every combustion line.

Frequently asked questions