My Candle Burns Correctly at 6% Fragrance but Becomes Unstable at 10% — How Can Increasing Fragrance Load Alter Wick Behaviour?

What extra fragrance does to the fuel your wick burns

A candle that burns steadily at 6% and becomes unstable at 10% has not changed its wick, jar or wax. It has changed the recipe of the liquid in the melt pool. Every percentage point of fragrance you add displaces the same weight of wax, so at 10% in a 200 g candle you have 20 g of oil and 180 g of wax, against 12 g and 188 g at 6%. That shift sounds small on paper. At the wick tip it is not.

The wick draws melted fuel upward by capillary action. Wax and fragrance behave differently once they reach the flame: fragrance materials range from light, quick-evaporating top notes to heavy, viscous base notes, and none of them burn exactly like wax. As the fragrance share rises, the fuel reaching the flame becomes richer in these materials. The flame can grow restless, the wick tip can collect more carbon, and the combustion that was comfortably balanced at 6% can tip into sputtering, smoke or a mushroom cap.

There is a second effect. Wax can only hold so much fragrance comfortably within its crystal structure. As you approach and pass that comfortable point, some oil sits less securely bound. It may appear as surface sweating in the cold candle or as a slick of fragrance-rich liquid in the melt pool. Either way, the wick is being offered fuel it was not sized for.

Find the load where the burn changes, not just the endpoints

Most makers test 6% and 10% and see a good candle and a bad one. That tells you something went wrong between them, not where. The useful question is the exact step at which the flame stops being steady, because the answer often sits well below the maximum and determines your best commercial load.

Use a single oil and a single wax for the whole ladder. Here the worked example is CSI Woody Oud, whose product page lists a citrus and spice top, oud and patchouli heart, and a woods, amber and musk base, with a soy range of 6–10% and a stated cure of 48–72 h. The wax is CSI 464 soy flakes at ₹507.40 per kg. Oil is priced at the 1 kg rate of ₹4,531.20.

The working for each line is oil grams × ₹4,531.20 ÷ 1000 and wax grams × ₹507.40 ÷ 1000. For instance, at 9%: 18 g × ₹4,531.20 ÷ 1000 = ₹81.56 for oil and 182 g × ₹507.40 ÷ 1000 = ₹92.35 for wax. Wicks, jar and labour are left out so you can see the effect of load alone.

Reading what the flame is telling you at each step

Instability at higher load rarely looks the same in every candle. Recording which symptom appears first helps you decide whether the fix is load, wick or both.

It is tempting to answer instability at 10% with a smaller wick. Sometimes that works, but it can also leave you with a narrower melt pool, weaker throw and a tunnel that wastes the extra fragrance you paid for. Before you re-wick, ask whether 10% is buying you anything the lower steps did not.

Respect the wax's stated ceiling and the oil's range

CSI 464 states a fragrance load up to 10%, which makes 10% the ceiling rather than a target for that wax. CSI Luxury Soy Wax Chunks state a maximum of 13% of wax weight, and CSI 468 coconut soy states up to 13%. Note the difference in basis: product pages phrase their figures as a percentage of wax weight, while this series calculates load as a percentage of total candle weight, so convert carefully before you compare numbers across pages.

A higher stated maximum on a different wax does not mean your oil will burn well at that level. It means the wax can retain that much oil. Wick behaviour is a separate test, and the load at which the flame destabilises may sit below the wax ceiling in any wax. Woody Oud's own stated range for soy is 6–10%, so testing it beyond 10% in soy would leave the range the product page gives.

Decide with throw, flame and cost together

Suppose the ladder shows a steady flame up to 8% and the first unsteady burn at 9%. Your commercial load sits at 8% or below, and the question becomes whether 8% is noticeably better in the room than 7%. If the throw difference is marginal, 7% gives you more headroom from the threshold, which protects you against small weighing variations in production.

The cost gap between 10% and 8% for this oil is ₹90.62 − ₹72.50 = ₹18.12 per candle. Across a run of 100 candles, that is ₹18.12 × 100 = ₹1,812.00 spent on oil that, in this example, made the burn worse. Here is the honest recommendation: if 8% burns cleanly and meets your throw target, do not pay for 10%.

When re-wicking is the right answer

Occasionally the ladder shows the opposite pattern: the flame is steady at every load but the throw only becomes acceptable at the top of the range. In that case the oil may need its full load and the wick may need a small increase to open a wider melt pool, tested one step at a time. That is a different problem from the one on this page, and it should be treated as its own experiment with a fresh set of candles.

Whatever you decide, write the threshold down. Knowing that this oil destabilises at 9% in CSI 464 with your wick is more useful than knowing it works at 8%, because it tells your production team how much margin they have.

Where this page fits

CSI already has guides that cover parts of this question. This page answers the specific oil-in-wax question above; these go deeper on the rest:

Three things to buy for this job

Frequently asked questions