How Many Reworked Test Candles Should I Validate Before Remelting an Entire 500-Unit Batch?

Why one number is the wrong question

You have 500 sweating candles, a dilution calculation and a plan to remelt the lot. The sensible instinct is to test first. The usual follow-up question — how many test candles? — has no single right answer, because the number depends on what each candle is being asked to prove.

A reworked candle has to pass several separate checks. It must stay dry in normal storage. It must stay dry under the warmer conditions your customers or couriers may expose it to. It must burn cleanly through to the bottom with the wick you choose, and its throw must still meet your standard. A single candle can only do one of those destructively, and one result tells you nothing about consistency. So the right question is: how many conditions, and how many candles per condition?

There is a second reason for stages. A rework that works in a 1 kg pot can still fail in a 10 kg melter, because mixing, holding time and pour duration all change with batch size. A small pilot proves the formula; a medium run proves the process.

The maths for each stage

Here is an illustrative case. The 500 candles are 200 g fills in CSI 464 at 10% of total weight, and testing points to 8% as the target. The whole batch holds 500 × 200 g = 100,000 g, with 10,000 g of oil. At 8% it must weigh 10,000 ÷ 0.08 = 125,000 g, so the full rework adds 25,000 g of wax. Split into stages:

The total comes to 624 rather than 625 candles because each stage rounds down to whole candles; the half-candle of wax left from stage 2 is a top-up for the next pour. In practice you will recover a little less than the theoretical weight from each jar. Weigh what you actually recover at each stage and dilute that figure.

The whole rework needs 25 kg of CSI 464. CSI lists no 25 kg pack, so that is two 10 kg packs and one 5 kg pack: 2 × ₹5,074.00 + ₹2,537.00 = ₹12,685.00. Buy the 500 g pack (₹260.00) for stage 1 first; buy the rest only after stage 1 passes.

Stage 1: twelve candles, twelve jobs

Assign every pilot candle before you pour, and write the assignment on the batch sheet. The split below is a suggested starting point.

Pilot spend at CSI prices, assuming you reuse the original jars and buy a five-pack of matte jars for the two extra candles: ₹260.00 (wax) + ₹354.00 (five matte jars) + ₹118.00 (Eco C1, 20) + ₹94.40 (Eco C2, 10) = ₹826.40, excluding shipping and GST.

Stage 2: fifty candles through the real melter

If the pilot passes, do not jump to the remaining 440. Remelt fifty originals in the melter you will use for the full job, at the batch size you intend to work in. That is where the process differences appear: the larger mass holds heat longer, takes longer to mix evenly, and takes longer to pour, so the first and last candles of a run can differ.

From the 62 candles poured, pull samples from the start, middle and end of the pour — three of each is a reasonable starting point — and put them through the same storage and warm-room checks as the pilot. Burn two with the wick chosen in stage 1. Keep the rest on hold, labelled, until the checks pass; they become saleable stock only once they do.

Stage 3 and release

With two stages passed, the remaining 440 originals can go through the melter — but as a series of melts, not one event. Work in batches your melter and team can mix and pour within your normal working time, and treat each melt as its own lot with its own number on the batch sheet.

For each melt, record the recovered weight, the wax added, the recalculated load, the mixing temperature and stir time, and the pour start and finish times. Pull a few samples from the start, middle and end of each pour and hold that lot until its samples pass the same storage checks as stage 2. The warm-room check can be reduced to one or two candles per lot once the first lots have passed, but should not disappear.

Release lot by lot, not batch by batch. If lot five fails while lots one to four pass, you have 110 or so candles to investigate rather than 550, and the cause — usually a process slip on that day — is fresh enough to find.

When the last lot is released, file the whole record together: the original batch, the pilot assignments and results, the scale-run samples, and each production lot. That file is what lets you answer a customer or a retailer who asks how you know the candle they bought will not weep — and it is the template for the next rescue, if there ever is one.

What testing can and cannot promise

No number of test candles guarantees every candle in the batch. A small pilot catches a formula that fails consistently, which is what a sweating rework usually does. It will not catch an occasional fault from a badly mixed corner of one melt. That is what stage 2's start, middle and end samples are for, and why stage 3 should be sampled the same way, melt by melt.

If any stage fails, stop at that stage. A failed pilot means the formula is wrong: try a lower target, or a different oil or wax, before remelting more originals. A failed scale run means the process is wrong at size: fix mixing, temperature or batch size, and repeat stage 2. Either way, the untouched originals are still in their jars, still on hold, and still recoverable.

Testing in stages costs a few days and less than a thousand rupees in materials at stage 1. Remelting 500 candles on the strength of arithmetic alone risks turning a 500-candle problem into a 624-candle one.

Where this page fits

CSI already has guides that cover parts of this question. This page answers one sweating decision; these cover the neighbouring questions:

Three things to buy for this fix

Frequently asked questions