I Have 10 Kg Left From My Old Wax Batch and 25 Kg From a New One — How Should I Transition Without Creating Unexplained Changes in Finished Candles?

Your old lot is runway, not a leftover

Most advice on this situation is about rotation: use older material first so it does not age on the shelf. That is sound, and it still applies. But a goods-in view adds a second point that is easy to miss. The old lot is the only stock you have that is already approved, so it is also the stock that buys you time to approve the new one.

Think of it as a race with a known finish. The old lot will cover a certain number of candles at your usual production rate. The new lot needs a certain number of days to screen, pour, cure and burn. If the runway is longer than the qualification time, you can test properly and switch without any pressure. If it is shorter, you are heading for the morning when the old bag is empty and the only wax on the shelf is untested.

So the first job on delivery day is not to open the new bags for production. It is to do the arithmetic, start the qualification clock and label everything with its status.

The runway arithmetic

Take a maker pouring 150 g candles in thick-walled apothecary jars, with Bergamot Amber at 9% of total candle weight. Each candle takes 150 × 0.09 = 13.5 g of oil and 136.5 g of wax. She holds back 500 g of each lot as a sealed reference, a suggested starting point rather than a rule.

At her rate of 40 candles a week, the old lot lasts a little under two weeks. The new lot's qualification, allowing a same-day screen, a paired pour, the soy product page's stated 48–72 hour minimum cure and two evenings of burning, fits inside roughly one week. She has room, but not a lot of it. If she produced 80 candles a week, the old lot would last under a week and she would need to either slow production of this line or start qualification before the delivery even arrived, using a sample from the supplier.

The transition sequence

Why the bridge pour is worth an extra hour

The paired test tells you whether the new lot is acceptable. The bridge pour does something different: it anchors your production history. Two candles made on the same day, by the same person, from the same oil bottle and wick packet, one from each lot, are the most direct comparison you will ever have of what changed at the cut-over.

Those two candles earn their keep later. If a customer reorders in two months and says the candle seems different, you can burn the bridge pair and see whether the change you are being told about lines up with the lot change or not. If it does not, you look elsewhere: the oil, the wick, the season. If it does, you have a clear, dated story for the supplier.

Staging the cut-over across several products

If one wax feeds several products, you do not have to switch them all on the same day. A staged cut-over moves the new lot into the lowest-risk line first and the most sensitive line last. A deeply coloured candle with a strong oil hides small differences in top finish and colour; a white, lightly scented candle in a clear jar shows everything. Starting with the forgiving line gives you a few more production runs of real-world evidence before the demanding line changes.

Staging has a cost. For a while two lots are open in production at the same time, which means two sets of labels, more care at the melter and a production log that must say which lot fed which batch. For a small workshop with one melter, that extra handling can create more risk than it removes. Decide deliberately, and if you stage, write the plan down: which product switches on which date, and which lot each batch sheet should show.

If the new lot fails before the runway ends

This is where planning pays off. Because you started qualification on the day the delivery arrived, you know about a problem while there are still old-lot candles to be made. Use that time well. Share your screen notes and paired-test photos with the supplier, ask whether anything changed in the product, and agree what happens next. If the supplier is CSI, the channel is WhatsApp +91 7397976926; CSI does not publish lot-specific data on its product pages, so your comparison is the evidence, and a lot that fails goes back in quarantine, including when it came from us.

What you should not do is let the runway end and then release the failed lot because nothing else is on the shelf. If production has to pause on one line for a few days, that costs less than a season of candles that behave differently from the ones your customers reordered.

Where this page fits

CSI already has guides that cover parts of this question. This page covers the goods-in check for the question above; these go deeper on the rest:

Three things to buy for this job

Frequently asked questions