My New Oud Fragrance Makes the Wick Mushroom More Than the Previous Batch at the Same 8% Load — Can Fragrance-Lot Variation Affect Combustion?

Yes, a fragrance lot can change how a wick burns

A mushroom is the carbon cap that builds on a wick tip when fuel reaches the flame faster than it can burn completely. The flame gets bigger and dirtier, the cap glows and can drop into the melt pool, and soot marks appear on the jar. The usual causes are well known: a wick that is too large for the jar, a fragrance load that is too high, or fragrance materials that burn less cleanly than the wax around them.

That last cause is why the answer to your question is yes. Fragrance oil is part of the fuel. Oud-style blends tend to be built on heavier woody, resinous and balsamic materials, and CSI's Woody Oud page describes that structure: citrus and spice at the top, oud and patchouli in the middle, woods, amber and musk in the base. If one lot carries a little more of the heavy base or a different source of a key material, the wick is burning a slightly different fuel at the same 8% — and heavy materials are the ones more likely to leave carbon behind.

But "can" is not "did". A new lot of oil arriving at the same time as a new wick delivery, a new wax bag, a hotter week or a change in trimming habit is extremely common, and each of those can produce more mushrooming on its own. Before you raise it with the supplier or change your wick, you need to know which material moved.

Rule out the cheap explanations first, in ten minutes, before you pour a single test candle. Re-weigh a dose of the new oil on your scale to confirm the load really is 8% and not creeping up through a measuring habit. Check whether production wicks are being trimmed as usual, or whether a new team member has stopped trimming between burns. Look at where the problem candles were burned: a fan, an open window or an air-conditioner vent will make any flame flicker, smoke and build carbon. If one of these explains the change, the lot never needed investigating.

The swap test: separating oil from wick

The cleanest way to attribute mushrooming is a small swap design. Instead of comparing old candle with new candle, you cross the two suspects so each combination appears once.

Pour all four on the same day from one wax bag, at 8% by total candle weight, with oil added comfortably below its flashpoint. Woody Oud's page does not publish a flashpoint, so request the MSDS and use the figure it gives. If you can spare the oil, make each combination twice, giving eight candles, so one odd wick does not decide the result.

If the wax bag is also new since your last good run, hold that constant too by pouring every candle from the old bag if any is left. You want one bag, not two, behind all four combinations.

How to run and score the burn

Read the results across the table rather than candle by candle. If B and D mushroom and A and C do not, the oil lot is responsible. If C and D mushroom and A and B do not, the wick delivery is. If all four mushroom more than your production records suggest, look at something common to all of them — the wax bag, the room or the trimming. If only D is bad, the two changes may be compounding each other, which is worth telling both the oil and wick supplier.

Worked example: what the swap test costs

Say you use Woody Oud at ₹4,531.20 per kilogram in 200 g candles in matte jars with thin Eco wicks. At 8%, each candle carries 16 g of oil, which is 16 ÷ 1,000 × ₹4,531.20 = ₹72.50 of oud, plus 184 g of wax.

Two practical points follow. First, the test is only possible if you kept enough of the old oil and a few old wicks. A 20–30 ml oil retain supports the lean version but not the full one, so for oils you use heavily, a larger retain is worth considering. Second, the finished test candles are not wasted if they pass cleanly; if they fail, they have done their job by keeping a problem lot out of a production run.

Acting on the result

You may be tempted to keep the new oil and simply size down the wick, or drop the load to 7%. Either can work, but either one turns your approved candle into a new formula that needs its own full burn test to the bottom of the jar. Make that choice deliberately, after the supplier has answered, and not as a quick fix at goods-in. Record the outcome against the invoice number and date received, since CSI product pages do not publish lot numbers, so the next oud delivery can be judged against this one.

Where this page fits

CSI already has guides that cover parts of this question. This page covers the goods-in check for the question above; these go deeper on the rest:

Three things to buy for this job

Frequently asked questions