Why the clock does not scale

In a 1 kg test, the spoon reaches every part of the pot. Each stroke drags wax from the bottom to the top and from the edge to the centre. After a few dozen strokes the whole batch has been folded over itself many times, and the oil is spread through it. Two minutes was simply how long that took.

In a 20 kg melter, the same stroke moves a much smaller share of the batch. The wax is deeper, so it takes more effort to lift material from the floor. The surface is wider, so the edges see less movement than the middle. Unless your stirring tool reaches the floor and you deliberately work every region, some parts of the batch may barely move at all in two minutes. Stir time is really a proxy for turnover, and turnover does not scale with the clock.

There is no published rule that converts a 1 kg stir time into a 20 kg one. Some makers double it, some triple it, and some stir until they are tired. None of that is evidence. The only honest way to know is to test the batch you are actually making.

Signs the batch is not mixed yet

Before running a formal trial, learn the visual clues. They cannot prove the batch is mixed, but they can prove it is not.

Technique matters more than minutes

Two people stirring the same batch for the same time can produce very different results. Before you measure time, fix how the stirring is done, otherwise your trial measures the person rather than the batch.

Reach the floor

The stirring tool has to touch the bottom of the melter. A short stick that only works the top third of a deep batch will leave the floor layer almost untouched however long you stir. CSI does not sell long mixing paddles; if you buy one elsewhere, look for a food-grade stainless or heat-safe tool long enough to reach the floor with your hand well clear of the wax.

Lift, do not whisk

Use slow, deliberate strokes that carry wax from the floor up to the surface, then move the tool to a new area. A figure-of-eight across the melter covers the centre and edges in turn. Fast whisking mostly spins the top layer and folds air into the wax, which can show up later as bubbles or rough tops.

Scrape the walls

Oil and cooler wax both collect against the walls. Run the tool around the inside edge every so often so that material joins the main body of the batch.

Write this technique down alongside the time. A written stir time without a written stir method will drift as soon as a second person starts making batches.

Run a sampling trial once per batch size

This trial takes one batch and some patience. It turns mixing time from a guess into a number you can write down and hand to someone else. The stir times below are suggested starting points; choose three that bracket what you think is needed.

Compare the pairs blind if you can. Ask someone else to label the jars with codes only, so you are not influenced by knowing which sample came from the floor. You are looking for the first stir time at which top and floor samples are indistinguishable in both cold and hot throw.

Worked example: 20 kg after a 1 kg test

Your approved 1 kg candle was stirred for 2 minutes after fragrance, which matches what Eco Soy CSI 400 states. You are now making 20 kg of scented wax at 8%: 18.4 kg of wax and 1.6 kg of oil, enough for 100 candles of 200 g before wastage.

You run the trial at 2, 4 and 6 minutes. After curing, the 2-minute pair is clearly different: the floor sample is stronger. The 4-minute pair is close but a second person can still tell them apart. The 6-minute pair matches. Your written standard becomes a minimum of 6 minutes of full-depth stirring for a 20 kg batch, plus whatever margin you choose, and 2 minutes stays the standard only for batches of the test size.

Those minute values are an illustration of the method, not a result you should copy. Your melter, stirring tool and wax may give a very different answer. The point is that you now have evidence instead of an assumption, and you only need to gather it once for each batch size you run regularly.

After the trial: keep the standard honest

Once the time is written, the sampling becomes a spot check rather than a daily task. Repeat the top-and-floor comparison when anything that affects mixing changes: a new batch size, a new melter, a different stirring tool, a new wax, or a fragrance with a noticeably different feel. Heavier, thicker oils can take longer to disperse than light ones.

Record the actual stir time on every batch sheet, not only the standard. If a customer later reports a weak candle, you want to know whether that batch was stirred for the full time or cut short because the pouring team was waiting.

Where this page fits

CSI already has guides that cover parts of this question. This page takes the production-floor angle; these go deeper on the rest:

Three things to buy for this job

Frequently asked questions