I Have 500 × 300 ml Jars but Only Want to Fill Them to a Specific Line — How Do I Calculate Actual Wax Requirement Before Production?

The line is a decision worth kilos

A 300 ml jar can be filled to many sensible lines. A higher line gives a fuller-looking candle and a longer burn; a lower line leaves more room for the wick, a lid and the flame's heat near the rim. Whatever you choose, the choice sets the wax order, and on 500 jars the difference between two reasonable lines can be several 10 kg bags. The table uses four illustrative lines, each described by the grams of water it holds.

Each 15 g step in water to the line moves the 500-jar wax order by about 6.07 kg and the oil by about 0.53 kg. Between the lowest and highest line in the table the wax need differs by 18.22 kg — nearly two 10 kg bags. So choose the line on the finished candle's look, safety and burn time first, then order to it; do not choose it after the wax arrives to use up whatever came.

Whichever line you choose, the factor in the table is still an approximation. It varies with the wax, how hot it was poured and how much it shrank. The weighed test pour is what turns the line into a number: in our example the 255 g line gave 222 g of set, topped-up candle rather than the estimated 224.4 g. Why 300 ml is not 300 g explains the gap in more detail, and planning from a water reading shows how to buy the test quantity.

When height maths works, and when it does not

Makers often ask whether they can skip the water test and calculate the fill from the jar's height. For one shape you can get close: a straight-sided cylinder holds volume in proportion to height. If the internal height from the inside base to the brim is 10 cm and your line is 8.5 cm up, the fill is about 300 × 8.5 ÷ 10 = 255 ml. That is how the worked example's 255 g line was chosen.

The height method fails in three common cases. Tapered jars are wider at the top, so the top centimetre holds more than the bottom centimetre. Thick or domed bases mean the outside height is not the inside height. Curved shoulders near the rim change the volume per millimetre sharply just where most fill lines sit. In all three the water test is quicker than the geometry, and more accurate. Use height maths to sanity-check a water reading, never to replace it.

Holding one line across 500 jars

On a long run, pourers tend to pour a little high, because a jar that looks slightly under-filled feels like a reject and a slightly over-filled one does not. Across 500 large jars the effect is real. In the illustrative 8 cm jar, pouring 1 mm high on average adds 4.42 g a jar and 2.21 kg across the run. That is wax and oil you bought for the loss allowance, spent instead on candles that are simply heavier than planned — and at the end of the run you are short.

You have two ways to handle it. Either add a drift allowance to the order — a labelled assumption such as "1 mm average over-pour" — or remove the drift with tools and checks. The second is usually cheaper. A graduated jug, a marked jig and a spot-weigh every twentieth jar cost very little against 2–7 kg of wax and oil.

The 500-jar order, priced

Using the example weighed fill of 222 g, three test jars and a 3% pour-loss allowance (working assumptions), with no separate drift allowance because the line is being held by weight:

Per jar that is about ₹151.76 of wax, oil and wick at the 50 kg and 1 kg rates, before the jar, and excluding labour, packaging, freight and GST. Which wick a 300 ml jar needs depends on its diameter and your wax; CSI does not publish wick sizes per diameter, so the Thin C1 and Thick C2 lines are priced for comparison, not as a recommendation. Burn-test both before you order 520. Testing three wick sizes sets that test up; double-wick candles covers the case where one wick is not enough for a wide jar.

Buying 100+ kg of wax

106 kg can be built entirely from listed bags, but the three container soy waxes do it very differently. Chunks and CSI 464 top out at 10 kg bags; Natural Soy Pearl goes to 50 kg. The bill for the same 106 kg:

Pearl is ₹8,730.40 cheaper than CSI 464 and ₹18,530.00 cheaper than Chunks on this order. That is a large gap, and it is a real one on listed prices. It is also a different wax, so the 222 g fill, the set surface and the burn all need re-testing in Pearl if your tests were poured in something else. For a run this size, ask CSI on WhatsApp to confirm that the bags you need are in stock together, and ask for a quote if you want one invoice across wax and oil; no volume discount figure is published, so do not assume one. Planning around 100 kg of wax covers the stock-and-promise side of an order this large.

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