How Do I Create Incoming QC for Fragrance Oils Covering Appearance, Odour, Viscosity Observations, Candle Compatibility, Hot Throw, Discolouration and Burn Behaviour?

What a specification is, and what it is not

An incoming specification is the written version of the decisions you make at goods-in. It says what you check, how you check it, what counts as a pass, and how often each check is done. It exists so that the same delivery gets the same decision whoever receives it, and so that when something goes wrong, you can see which check should have caught it.

It is not a copy of the supplier's data sheet, and it should not pretend to precision you do not have. CSI does not publish certificates of analysis, lot numbers, viscosity, specific gravity, refractive index or colour specifications for its fragrance oils, and many suppliers serving smaller makers are similar. Your spec therefore leans on comparison: against a retained reference, under matched conditions, with a written description of what a pass looks like.

This page is about the document itself. It assumes you already have an approved candle and a retained reference for the oil, and it shows how to turn those into a one-page specification.

The header: fixing the reference points

Every line in the specification is judged against something, so the header fixes those reference points before any parameter appears.

The nine parameters, line by line

The table below is an example specification. The criteria and frequencies are suggested starting points to adapt and validate, not a standard and not CSI policy.

Two lines deserve comment. Line 5 records a flow observation rather than a viscosity, because without a published figure or a viscometer you are only comparing two liquids at the same temperature. Write that plainly in the spec so nobody later mistakes it for a measurement. Line 8 uses an unscented control so that you can separate what the oil does to the wax colour from what the wax does on its own.

Recording results against the spec

Give each delivery a goods-in sheet that repeats the nine line numbers down the side, with a column for the result, one for initials and one for notes. A line that was not checked is marked as not checked, with the reason, rather than left blank. That small discipline is what lets you look back later and see whether a problem slipped through because a check failed or because it was never done. File the sheet with the invoice and the spec version that applied on the day.

Worked example: a spec for Gardenia

Gardenia, listed as Gardenia Tuberose, is a good test case because its product page publishes details the spec must honour. The flashpoint is given as 98°C and the page says to add the oil below 98°C. Vanillin is given as 0.2%, and the page states up to 10% in soy, up to 6% in paraffin, and 8–10% for luxury jars.

The header records those facts and nothing more. The approved recipe might be 8% in CSI 464 in a 200 ml matte jar with a thin eco wick, with the add temperature written into the method as below 98°C and the actual temperature recorded each time. That single instruction is the most important safety line in this oil's spec, and it only exists because the page published the figure.

For the quick checks, line 6 can be screened with a wax melt before any candle is poured. Wax melt clamshells cost ₹295.00 for a pack of 10, so one is ₹295.00 ÷ 10 = ₹29.50, and a small melt shows early whether the new delivery binds and throws like the old one. It does not replace the candle for lines 7 to 9. A confirmation candle at 8% of 200 g takes 16 g of oil; at ₹4,332.00 per kilogram, that is ₹4,332.00 ÷ 1,000 = ₹4.332 per gram, so 16 × ₹4.332 = ₹69.31 of oil.

For line 8, the low published vanillin suggests little discolouration from that source, but the spec still asks for the scented and unscented pair on the first delivery, because other materials can affect colour and because the page's figure describes the product, not your delivery.

Keeping the spec honest over time

A specification is a living document. After each delivery, note whether the checks were proportionate. If an oil passes cleanly every time, you may reduce candle checks to a set interval. If borderline results keep appearing, tighten the method, add a second assessor for strips, or make the confirmation candle routine. Change the version number and date whenever you change a criterion or frequency, and keep old versions so you know which rules applied to which delivery.

Update the header whenever the supplier tells you something new, and record the date and wording of their answer. If a supplier confirms a change to the oil, treat it as a new approval and start the spec again from a new reference.

Hold the spec to the same standard whoever supplies the oil. A delivery that fails a line stays in quarantine until the reason is understood, including when the supplier is us. And do not add lines that you will not actually check. A short spec that is followed every time is worth more than a long one that is skipped when the workshop is busy.

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

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