My 20 Kg Wax Batch Cools Much More Slowly than My 1 Kg Test Batch — Can Production Scale Affect Fragrance Mixing and Finished Candle Consistency?

Why the big pot keeps its heat

A pot loses heat through its surface and walls; it stores heat in its whole mass. Scale up the batch and the mass grows much faster than the surface it cools through, so each kilogram has less surface to lose heat from, and the pot cools more slowly. A 1 kg test in a small pot drops out of the pour window in minutes. A 20 kg pot can sit in it, or above it, for an hour or more. In the worked example on the chart, the test pot falls about 0.8°C a minute and the 20 kg centre about 0.05°C a minute, roughly 16 times slower. Your pots, lids and room will give different numbers, which is why you log them.

The pot also stops being one temperature. Wax against the steel wall and at the surface cools first; the centre stays hot. In the example the wall runs about 0.075°C a minute, a few degrees below the centre within the hour. A ladle or pitcher dipped near the wall gets cooler wax than one dipped in the middle, and unless you stir, the pot slowly separates into zones.

None of that is a problem with the wax or the oil, and it is why this page does not ask you to buy different materials. It asks you to manage the time the batch spends between oil-in and the last jar.

What slow cooling does to a pour session

The table ranks the effects we would suspect when a 20 kg batch is less consistent than the 1 kg test, most likely first. The ranking is editorial judgement, not measured data; each effect is a tendency, and CSI publishes no measured throw or composition data.

Rows 1 to 4 are what the cooling log is built to show, and all four have a process fix. Row 5 has its own diagnostic post; row 6 means the session is probably fine and the difference lies elsewhere, which the test-versus-production sheet finds.

The pot cooling log

Run it on a normal production batch. The worked example is 20 kg of CSI 464 at 8% of total weight with Fallen Leaves: 1,600 g of oil and 18,400 g of wax, 133 candles of 150 g (12 g of oil and 138 g of wax each), with 50 g left over in the pot and pitcher. At 3 candles per fill that is 45 pitcher draws.

The pour-window plan

Once you have one log, turn it into a plan for every 20 kg session. Four rules do most of the work.

1 · Split the batch into draws you can finish in the window. For CSI 464 in the 150 g Clear Glass Jar with Golden Lid, the window at the jar is 80–85°C: inside the wax page's 80–90°C and the jar page's "Safe for hot pour up to 85°C". Size each pitcher fill so its last jar is still at or above 80°C. If your log shows the last jar of a 3-candle fill dropping below 80°C in late draws, fill for two, pour faster, or warm the pitcher by rinsing it with hot wax from the pot before the draw. The other end matters too: early in the session, when the pot is near the top of its range, a fresh fill can read above 85°C, so let it fall to 85°C in the pitcher before the first jar.

2 · Restir the full depth before every draw. The same short routine each time, reaching the base and scraping the wall, with the stirrer head kept under the surface. Time it and write the time on the SOP (a worked example is 30 seconds with a paddle; yours depends on the pot and tool). Drawing from the centre of an unstirred pot gives you the hottest wax, not the average.

3 · Reheat only inside the page's range, and log it. If the pot centre drifts toward 80°C with draws still to go, reheat gently to a figure inside 80–90°C and restir before the next draw. Never above 90°C, the top of the CSI 464 page's range. Each reheat adds time at heat, so if the log shows several per session, the batch is too big for your pour rate.

4 · Keep oil-in to last jar short. Get jars, wicks and trays ready before the oil goes in. In our judgement the single biggest difference between a test and a production session is the hold while the bench gets organised. If the whole batch cannot be poured in a reasonable window at your pour rate, two 10 kg batches are the honest fix: they cost the same in wax and oil.

Reading the log and the retained candles

The stakes justify the paperwork. At ₹221.30 of materials per candle (excluding labour, freight, packaging and GST), the 133-candle batch is ₹29,432.53, and the last third of it, about 44 candles, is ₹9,737.08. That last third is the part a bad pour window affects. When first-versus-last differences remain after the plan is in place, the first-weaker-than-last post charts pour position against blind scores.

What not to buy for a slow-cooling pot

We sell the pitcher, the mixer and the thermometer on this page. You may need none of them: a long spoon, one pitcher, the thermometer you own and a batch split into two 10 kg pots can give you the same consistency.

Pitcher, mixer, thermometer, wax and oil

Five items, in the order the session uses them. Chosen on page statements, price per unit or gram, and stock on 26 September 2026; CSI publishes no measured throw or cooling data, so nothing is ranked on performance. Pitcher and oil tables list every size, with out-of-stock sizes flagged.

Frequently asked questions