Two Fragrance Oils Are Both Used at 8% but One Makes the Wick Mushroom While the Other Burns Perfectly — Why Can the Wick Respond Differently?

You already own the control candle

Most wick problems are hard to read because too many things are unknown. Is the wax consistent? Is the jar too wide? Did the wicks come from a different pack? Your situation is different. One fragrance at 8% burns cleanly in your system. That proves the wax, the jar and the general wick size can work together. The second fragrance, poured into the same system, mushrooms. The comparison has already narrowed the question to the oil and how the wick responds to it.

The existing guide on mushrooming covers wick sizing and load in general. This page is about the specific case of two oils side by side, and how to use the clean one to diagnose the other rather than re-wicking everything.

Rule out a production difference first

Before you look at chemistry, make sure the two candles really were made the same way. Small process differences can mimic a fragrance problem.

If any row differs, fix it and re-pour before drawing conclusions. If every row matches and the difference persists, the oil is the variable.

What makes two 8% oils burn differently

Take a pairing many makers run into: a spiced gourmand and a light white floral. CSI Cinnamon Vanilla lists cinnamon and clove at the top, vanilla bean and sugar in the middle, and cream and butter at the base. Its page publishes a flashpoint of 270°F (132°C) and vanillin at 2.5%, with a moderate discolouration risk in light wax. CSI Jasmine publishes a flashpoint of 185°C and 0% vanillin.

Those published figures do not predict the mushroom on their own, but they point to real differences in composition. As general principles:

Vanillin and heavy sweet materials tend to burn less completely than light floral materials. More unburnt residue reaches the wick tip and deposits as carbon.

Spice notes such as cinnamon and clove bring their own heavier aromatic materials into the mix, adding to the fuel's complexity.

Lighter florals release a larger share of their scent by evaporation from the pool, so less of the oil needs to be combusted at the wick.

You can add two simple bench observations to the published data. First, dip a clean bamboo stirrer into each oil and watch how quickly it runs off; a noticeably thicker, slower oil is worth flagging, because viscosity affects how fuel climbs the wick. Second, look at the colour of each oil in a clear beaker against white paper. A deeper amber or brown oil often signals heavier sweet or resinous materials. Neither observation is a measurement, and neither replaces a burn, but both help you predict which of two oils is more likely to load a wick. Smell only; never put fragrance oil near your mouth.

A flashpoint is a safety figure, not a burn-rate figure, so do not read 132°C against 185°C as proof of anything about mushrooming. Use it for what it is: a ceiling for your addition temperature. Add each oil below its own published flashpoint and at your wax's stated temperature.

The 2×2 cross test

Now make the oil difference measurable. The aim is to find out whether the mushroom follows the oil or the wick, which a single comparison cannot tell you.

Scoring carbon consistently is harder than it sounds, because a mushroom looks different in dim light and after the flame is snuffed. A simple habit helps: photograph each wick against the same white card at the end of every session, before trimming, and file the photo under the cell name. After three or four sessions you can lay the photos side by side and see the trend, which is far more reliable than remembering what the wick looked like on Tuesday. If one cell improves steadily while another gets worse with each burn, that trend is your answer, even if any single session looked ambiguous.

Decide per oil, not per jar

The most common outcome is the first row: the light floral is happy where it is and the heavier gourmand wants a step down. Record that as two approved combinations in the same jar, not as a mistake to be averaged away. Choosing one compromise wick for both oils usually makes one of them worse.

If the gourmand only cleans up at a lower load, check its cost. At 8% in a 180 g candle, Cinnamon Vanilla uses 14.4 g at ₹4,554.80 per kg, which is 14.4 × ₹4.5548 = ₹65.59 of oil. At 7%, it uses 12.6 g, which is 12.6 × ₹4.5548 = ₹57.39. Jasmine at 8% uses 14.4 × ₹3.923 = ₹56.49. A lower gourmand load can land its oil cost close to the floral's, which is a useful side effect of fixing the burn.

If neither a smaller wick nor a lower load produces a clean, steady burn with an acceptable throw, the oil may simply be the wrong match for your wax and jar. Say so in your notes and test an alternative from the same family, rather than stacking fixes that each cost you throw.

Finally, share the lesson with the rest of your range. Any other oil with a heavy sweet heart or a published vanillin figure should start its wick test on the gourmand wick you just found, and any other light floral can start on the approved one. The two-oil comparison has just given you a sorting rule for every future fragrance.

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:

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Frequently asked questions