Cosmetic or functional: the short version and the first test

A wet spot is commonly described as a place where the wax has separated from the glass and left a thin air gap. Seen through clear glass, that gap reflects light differently from wax pressed tight against the jar, so it reads as a dark, damp-looking patch. There is no liquid in it. That description is why most candle makers treat wet spots as mainly cosmetic: the wax is still in the jar, the wick is still centred, and the fuel the flame draws on is the same wax as before. CSI does not publish adhesion or burn data for any wax, and we are not going to claim proof in either direction. What we can give you is the single test that settles it for your own candle in a week of evenings.

The test is a paired burn. From one batch — same wax lot, same oil bottle, same load, same wick pack, same jars, same pour — pick a jar with obvious wet spots and a jar with none. Burn them side by side, in the same room, for the same time, and record the same eight lines for each: whether the melt pool reaches the glass, how deep it is, how long it takes, flame behaviour, a jar-side reading taken the same way on both, weight loss, whether a ring of wax is left on the wall, and whether you can see liquid wax running into the gap. Do that for three pairs. If every line matches, the spot is cosmetic for that candle and the job is to fix the look. If one line differs in the same direction on at least two of the three pairs, the spot is also a burn question and needs investigating before you sell more.

That is the whole answer in two paragraphs. The rest of this page explains why each line is on the record sheet, how to choose fair pairs, what to photograph and when, how much the test costs in burned candles, and what to buy — or not — depending on the result. It sits in the second half of the section on why wax pulls away from the glass, which starts from the patch you can see; this page starts from what the patch might do once the candle is lit.

Why most makers call it cosmetic, and why that is not proof

Soy waxes are commonly described as contracting as they cool and crystallise. If the wax shrinks away from the glass in one area while staying attached elsewhere, you get a patch. The reasons a jar ends up patchy are the subject of the whole section: why the patches look dark when there is no liquid, tiny scattered spots versus large patches, spots straight after cooling versus days later and whether contraction alone can cause them when everything else is right. None of those causes change the chemistry of the fuel. The wick still sits in the same wax, carrying the same oil at the same load, so the flame has no direct way of knowing whether the outer skin of the candle is touching the glass.

That is the argument for "cosmetic". It is a good argument, and it is also an argument rather than a result. There are two honest reasons to test it. The first is that a container candle finishes each burn at the wall, and the wall is exactly where a wet spot lives: whether the pool reaches the glass, whether it leaves a ring, whether melted wax runs into the gap, all happen at the place the spot changed. The second is that wet spots and burn faults can share a cause. A jar that cooled fast in a draught, a jar that was cold when poured, an oil that set unevenly — the same condition that pulled the wax away may also have affected the top, the wick seat or the set of the wax around the wick. If a spotted jar burns worse, the spot may be a symptom rather than the cause, and that matters for what you change.

So the test is not "does a wet spot damage a candle" in general. It is "in my jar, with my wax and my oil, does a candle that came out spotted burn differently from one that came out clean". That narrower question has an answer you can get this week, and it is the only answer that should decide whether you spend money on the look.

The paired burn test, step by step

The cleanest way to get fair pairs is to make them on purpose. Pour one batch of ten in CSI's Clear Glass Jar with Golden Lid (150 gram), the series' default jar because it is the one clear CSI jar with a published fill: its product page states approximately 150 g of wax and "safe for hot pour up to 85°C". At 8% a 150 g candle is 12 g of oil and 138 g of wax. In Luxury Soy Wax CSI 464, whose page gives an 80–90°C melt/pour working range, the jar's own limit means you pour at 80–85°C — the overlap of the two statements — and record the exact figure you used. Ten jars poured together will usually sort themselves: some come out spotted and some do not. If every jar comes out clean, you have learned something useful about your process; if every jar comes out spotted, see the full wet-spot diagnosis before burning anything.

The record sheet and the house spot scale

Two scales are needed: one for how spotted a jar is before you burn it, and one for how it burns. Both are your house standard — there is no industry scale for wet spots and no industry threshold for acceptable adhesion. The examples below are labelled working practices; adapt them, then never change them between tests, because a grade only means something next to other grades taken the same way.

Two notes on the record. The jar-side reading is there to compare two jars, not to pass or fail one: CSI publishes no numeric jar-temperature limit and there is no figure on this page to judge against. Use whatever tool you have — the back of your hand at a marked point is a crude but consistent comparison; a non-CSI infrared thermometer is better — and take it at the same point and the same minute on both jars. The weight line turns into consumption: weight lost divided by hours burned gives grams per hour, and two candles from one batch with the same wick should burn at similar rates. A large difference between a spotted and a clean jar is worth a second look regardless of the spot.

Decide in advance what counts as a real difference. A working rule: a line counts as different only if it differs in the same direction on at least two of the three pairs, on the same burn number. One pair, one burn, one millimetre is noise. Write the rule at the top of the first sheet before the first wick is lit; a rule invented after you have seen the numbers is not a rule. What to record when comparing adhesion builds the full record for a wax comparison, and how much variation is normal covers how to set the spot-grade threshold you will sell to.

Reading the result: four outcomes

Almost every paired burn lands in one of four places. Read them in order and stop at the first that fits.

The first outcome is the common one, and it is good news with a commercial sting. If the spot is cosmetic, the candle performs exactly as well as an unspotted one — but a customer looking through clear glass does not know that. Customers who think the spots are oil or moisture covers what to say and what to change. Why spots vanish in frosted or coloured jars explains the optics, and choosing a frosted jar instead of changing wax prices the vessel change. A cosmetic result also makes it fair to ask whether the spot is worth fixing at all for your price point — accepting minor wet spots for better throw and burn is where that trade-off lives.

The priced test batch

If you already have a batch with spotted and clean jars from one pour, you need nothing from us: pair them and burn. If you want a fresh, fully recorded batch, here it is in listed, in-stock CSI packs. Ten Clear 150 g jars at 150 g each, CSI 464, Lavender at 8%, one Eco Thin C1 wick per jar plus two spare, and a 5% pour-loss working allowance on wax and oil. Wax per jar is 138 g; oil is 12 g.

That is ₹267.94 a jar at test-kit prices, with 51 g of wax and 4 g of oil left over. The wick in this kit is an example line only: CSI does not publish a wick size for this jar, so if you have not burn-tested a wick in it, do that first — a wick that never reaches the glass will make every pair look the same for the wrong reason. Non-CSI items you may want are labelled examples, not prices: a grid sheet or marked acetate sleeve for grading, and a phone stand for side photos.

What the test costs in candles

A paired burn destroys six saleable-or-nearly-saleable candles, so price it honestly. At production rates — CSI 464 at the 5 kg rate of ₹507.40 a kilo, Lavender at the 1 kg rate of ₹5.22 a gram, an Eco Thin C1 wick at ₹5.90 and the Clear 150 g jar at ₹94.40 — one 150 g candle carries the material cost below. It excludes labour, labels, packaging, freight and GST.

Set that ₹1,397.84 against what it decides. Take an example batch of 100 candles with an example 20% spotted — 20 jars; replace both figures with your own. If the paired burn says the spots are cosmetic, those 20 jars are fit to burn and the question becomes how to present or prevent the look, not whether they are safe to sell. If it says the spots go with a burn difference, you have found it on six candles instead of hearing about it from customers. Either way the test costs less than the material in 6 candles — exactly the six you burned. Load is worth one glance while you are here: in CSI 464, whose page states up to 10%, the Lavender line costs ₹46.99 at 6%, ₹62.65 at 8% and ₹78.31 at 10% per candle. Do not change load during this test — it is a different variable, and the 6% versus 10% adhesion question owns it.

The decision rule

Apply after three pairs and at least three burns per pair. Stop at the first line that is true. It is written so that two people reading the same sheets reach the same decision.

Notice that no line ends in "buy a new wax now". That is deliberate. A wet spot that is cosmetic is a reason to fix your process or your presentation, and a wet spot that goes with a burn difference is a reason to investigate cooling, glass temperature and the wick before materials. A second wax becomes a fair purchase only when the free rungs are exhausted — and then it is a 500 g or 1 kg test bag, not a 10 kg production bag. Whether adhesion should become a major wax criterion covers when the look alone justifies that test.

The CSI products in this test

Frequently asked questions