I'm Scaling Production but Reject Rates Are Increasing — How Do I Calculate Whether Faster Output Is Actually Reducing the Number of Sellable Candles per Day?

Candles poured is the wrong number to celebrate

When a team is pushed to go faster, the number that gets reported is the number poured. It rises, and everyone feels the effort worked. Then QC runs, and more candles than usual are set aside: rough tops, leaning wicks, wax on the glass, under-weight fills, the odd spill. The pile of rejects grows quietly while the headline number looks healthy.

The only output that matters is the number of candles that pass QC and can be sold. Everything else is material, labour and time converted into waste. So the question behind this page is simple: as you speed up, does the number of sellable candles per day actually rise?

Often it does, up to a point. Beyond that point, the extra pace adds mainly rejects. The job is to find where that point is for your team and your candle.

The calculation: sellable = poured × (1 − reject rate)

Take a workshop that has been pouring 300 candles a day with a 3% reject rate. That gives 300 × 0.97 = 291 sellable candles. Management wants more, so the team is pushed.

Going from 300 to 400 poured is a real gain: 69 more sellable candles a day. Going from 400 to 480 adds 80 pours and zero sellable candles, because rejects rise from 40 to 120, exactly the extra 80. Going to 500 actually loses sellable candles. The team is working harder for less.

You can also turn the formula round to test a proposed speed-up before trying it. To beat 291 sellable a day by pouring 400, the reject rate must stay below 1 − 291 ÷ 400, which is about 27%. That is only break-even on count. It ignores the material inside the extra rejects, which is where the next calculation comes in.

Measure sellable candles per 10 kg batch

A 10 kg batch of scented wax fills 50 candles of 200 g exactly, or 48 after 5% planning wastage. Every reject lowers the number of sellable candles you get from that same 10 kg. This is a better efficiency measure than candles per day, because it shows what speed costs in material.

These figures assume 50 pours per 10 kg and count only rejects. Spills and residue come on top, so your real sellable figure per batch will sit a little lower. The trend is what matters: from 48.5 sellable candles per 10 kg at the original pace down to 37.5 at the pushed pace, a drop of more than a fifth in what the same wax produces.

At 480 a day, 24 kg of scented wax goes into rejected candles every working day. At 8% of total weight, that is 22.08 kg of wax and 1.92 kg of fragrance oil. In pack terms, it is more than two 10 kg packs of wax, such as Luxury Soy Wax CSI 464 at ₹5,074.00 per 10 kg, and nearly two 1 kg packs of an oil such as Sandalwood at ₹5,026.80 each, every day. Add a wick and a jar for every reject; ready-made braided wicks alone are ₹12.00 each.

Can rejects simply be remelted?

It is tempting to treat rejected candles as free wax. Some rejects, especially fill-weight errors caught before the wax sets, can be corrected immediately. Once a candle has set, reclaiming it is less simple than it looks.

The wax contains fragrance oil, and fragrance oils are volatile; each additional heating cycle can reduce what remains. It may also contain dye, and it must be separated from the wick and the jar. Reclaimed wax is therefore not the same material as the batch it came from, and blending it into a production batch changes that batch in ways you have not tested.

Labour is lost too. Every reject was weighed for, melted, poured, cured, checked and then removed. Reclaiming it adds more handling. The cheapest reject is the one that never happens.

Find the rejects that rise with speed

Not every reject is caused by speed. A cracked jar from a poor lot will be rejected at any pace. To know what faster working is doing, log each reject by cause and compare a normal day with a pushed day.

Once the speed-linked causes are removed, the curve shifts. The same 480 pours might then run at a much lower reject rate, and the extra speed finally becomes extra sellable output.

Choosing the right pace

Run at the pace where sellable candles per day peaks, not where pours peak. In the example, that is around 400 a day. Pushing beyond it only wastes wax, oil, wicks and jars until the causes are fixed. Write the chosen pace into the SOP, and review sellable per day and per 10 kg batch weekly. If either falls, look at the reject log before looking at the team.

A weekly speed review

Keep one short table on the wall: date, candles poured, rejects by cause, sellable, scented wax used and sellable per 10 kg. Read it together at the end of each week. It turns an argument about whether people are working hard enough into a shared look at the numbers, and it shows quickly whether a process change has worked.

When the review shows a fix has lowered speed-linked rejects, try the faster pace again in a controlled way: one pourer, one fragrance, one full day. If sellable per 10 kg holds, extend it to the rest of the team. If it drops, the fix was incomplete, and you have lost one day of extra rejects rather than a month.

Watch safety at speed as well. Rushed pouring with hot wax means more spills on hands and benches, and more jars handled while hot. A pace that causes burns is not a production rate anyone should plan around.

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