Incoming Raw Material Inspection: Catch the Problem Before Production
The parcel arrived, the bottle went on the shelf, a week later it went into production and the batch did not smell right. Whose fault is it? The only way to answer that question is for the raw material to have been checked the moment it came through the door. Incoming inspection means verifying a raw material by its documents, its appearance and its odour before it enters production.
In a small workshop this step is often skipped: "the supplier is reliable, what could go wrong." But the fault may lie not with the supplier but in transit, in the warehouse, on the label or in a lot change. The check takes ten minutes; a spoiled raw material that enters unchecked takes a batch with it, and sometimes a customer.
This article gives a workable accept–reject list for fragrance oils and raw materials. Tests that require laboratory equipment are marked separately; most checks are done with a balance, glassware and your nose.
Document Check: Is What Arrived What Was Ordered?
The first check is on paper, not physical. Five documents are compared.
| Check | What is compared | Reason for rejection |
|---|---|---|
| Purchase order – delivery note | Product name, code, quantity, number of packages | Missing or different product |
| Label – delivery note | Product name, lot number, production and expiry date | Label illegible, no lot, date expired |
| CoA (certificate of analysis) | Is the lot number the same as on the label; are appearance, density and refractive index values within specification | No CoA, lot does not match, value out of spec |
| SDS | Is the current version to hand; does the hazard class match the label | SDS missing or outdated (quarantine, not rejection) |
| IFRA / allergen declaration | Available for fragrance oils, prepared against the current amendment | Document missing (quarantine; production waits) |
The most common error in the document check is that the lot on the CoA differs from the lot on the bottle. The supplier may have sent the certificate for the previous lot; that document does not represent this bottle. The material stays in quarantine until the CoA for the correct lot arrives.
Physical and Sensory Inspection: Step by Step
If the documents are complete, move on to the physical inspection. The order matters: packaging first, then appearance, odour last.
- Packaging and seal
Is the bottle dented, is the cap intact, is the tamper-evident ring unbroken, are there traces of leakage on the outside? Leaking packaging is a reason for rejection; dented but non-leaking packaging is accepted with a note.
- Weighing
Does the gross weight match the quantity on the delivery note? A tare difference of a few per cent is normal; ten per cent short means loss in transit or leakage.
- Appearance
Take a small sample into a clear glass tube and hold it up to the light. Colour, clarity, sediment, separation. If the specification says "pale yellow, clear", a dark brown or cloudy sample is out of spec.
- Density
Weigh a measured 10 ml sample on a precision balance or use a pycnometer. It should be within ±0.005 g/ml of the CoA value. A deviation is a sign of the wrong product or a diluted product.
- Refractive index (if you have a refractometer)
One drop is enough. It should be within ±0.002 of the CoA. Together with density, this is the strongest identity check.
- Odour: compare with the retain sample
Put the new lot and the approved retain sample on blotters at the same dilution (10% in ethanol); smell them side by side at 10 minutes, 1 hour and 4 hours. If there is a difference, confirm it with a triangle test. A lot whose odour differs noticeably from the retain sample is not accepted.
- Record and label
Write the results on the incoming material form, stick an "accepted – date – inspected by" label on the material, set aside a retain sample and put it on the shelf.
Accept, Conditional Accept, Reject: Decision Rules
At the end of the inspection three decisions are possible, and the rule for each must be fixed in advance; otherwise the decision gets made under the pressure of "production is tight, let's just use it".
Accept: All documents complete, physical values within spec, odour consistent with the retain sample. The material goes on the shelf and is released for use.
Conditional accept (quarantine continues): A document is missing but the physical inspection is clean (CoA or SDS not yet received); or there is a small difference in appearance but odour and density are consistent (for example a slightly darker colour). The material stays in quarantine and is released when the gap is closed or when the responsible person gives written approval. The name of the person approving goes in the record.
Reject: Wrong product, leaking packaging, density or refractive index out of spec, odour noticeably different from the retain sample, expiry date passed. The material is moved to a separate area with a "REJECTED" label and the supplier is notified in writing the same day; photographs and measurement results are attached to the notification.
The language of the rejection notice should be technical and numerical: instead of "the odour is off", write "density 0.912 (CoA 0.935); odour noticeably acidic compared with the retain sample; triangle test 5/5 identified the difference". This is the only language a supplier can respond to.
Frequently Asked Questions
The most common questions about incoming raw material inspection.
Is this inspection really necessary in a small workshop?
I do not have a refractometer; what should I do?
If I have no retain sample, what do I compare the odour with?
The value on the CoA is out of spec but the product smells fine; can I use it?
What happens if the supplier has changed lot?
How long does the inspection take?
How should I keep the inspection record?
What if the supplier will not take back rejected material?
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