Conclusion: Judge the Sample Against Criteria, Not by Preference
When a prototype sample arrives, the most dangerous judgement is "the feel is good, so let's proceed with this". Feel is only one evaluation axis; if colour, fragrance, viscosity, container compatibility or change over time falls outside the criteria anywhere, a problem is certain to appear after mass production.
Sample evaluation is carried out in the following four layers.
| Layer | What is examined | Nature of the evaluation |
|---|---|---|
| Sensory evaluation | Colour, fragrance, texture, feel on use | Judged by people. Criteria and recording method are set first |
| Physical properties | Viscosity, pH, specific gravity, solids content | Judged on measured values. Comparison is impossible unless conditions are aligned |
| Compatibility | Container, discharge volume, leakage, label | Judged on the combination of fill and container |
| Change over time | Changes at high temperature, low temperature and room temperature | Requires time. Skipping this causes failures in mass production |
1. Sensory Evaluation: Set the Criteria First
Sensory evaluation is recorded not as "good / bad" but as a scale of around five levels per item, with comments. Where there are several assessors, each records independently and the results are then compared.
| Item | Points to examine | How to record |
|---|---|---|
| Appearance | Colour tone, gloss, separation, sedimentation, air bubbles | Compare side by side against the standard reference. If there is a colour number, check against it |
| Fragrance | Intensity, duration, presence of alteration | Record immediately after application and several hours later separately |
| Texture | Spread, weight, stickiness, speed of absorption | Spread a fixed amount (0.1 g, for example) over a fixed area and compare |
| Feel on use | Feel after time has passed (tightness, greasiness) | Record the change after 30 minutes and after several hours |
| Change in appearance | Discolouration, drying, smudging after application | Check in combination with a base or another product |
Deciding the "standard reference" first is important. Without something to compare against, the quality of the second and later samples cannot be judged.
2. Physical Properties: Measure What Can Be Measured
Sensory evaluation varies from person to person. Items that can be measured are pinned down as numerical values.
| Item | Measurement method | Points to note |
|---|---|---|
| Viscosity | Brookfield viscometer or similar | Always record the temperature, rotation speed and measurement time alongside the value. Comparison is impossible under different conditions |
| pH | pH meter | Align the temperature conditions |
| Specific gravity | Calculated from weight and volume | Needed to calculate fill volume |
| Solids content | Dry weight method or similar | Effective for confirming reproducibility of the formulation |
For viscosity in particular, note that a value recorded without its measurement conditions cannot be compared. Even with the same formulation, the value changes if the measurement temperature differs by 5°C.
3. Compatibility Evaluation: The Most Frequently Overlooked Area
The compatibility of the fill and the container can only be confirmed at the sample stage. If it comes to light after mass production, the containers have to be remade.
| Check item | How to test | Indicative pass condition |
|---|---|---|
| Discharge volume | Press the pump a specified number of times and measure the weight | Within the tolerance against the stated value |
| Leakage | Leave inverted, on its side and after vibration | No seepage or leakage |
| Draw-up | Whether it can be used to the end | Residual volume within the expected range |
| Cap fit | Open and close a specified number of times | No loosening, cracking or squeaking |
| Label adhesion | Curved surfaces, lifting or peeling after time | No lifting at the edges |
| Material compatibility | Fill the product and store for a fixed period | No degradation, discolouration or odour migration |
| Legibility of labelling | Check under actual lighting | Required items can be read |
Discharge volume and draw-up change when the viscosity of the fill changes. Whenever the formulation is revised, these must be rechecked.
4. Change Over Time: The Minimum Checks Worth Running
Even a good sample can separate, discolour or change in viscosity as time passes. At a minimum, the following should be carried out.
| Condition | Indicative period | What to check |
|---|---|---|
| High temperature (40°C, for example) | 2–4 weeks | Separation, discolouration, odour change, effect on the container |
| Low temperature (5°C, for example) | 2–4 weeks | Solidification, separation, condition after returning to room temperature |
| Room temperature | 2–4 weeks | Change under conditions close to actual use |
After storage at high or low temperature, return the sample to room temperature before carrying out sensory evaluation. This is because the condition after returning is closer to actual use. Where long-term stability testing is required, testing by a specialist organisation is arranged separately.
5. How to Approve: Record What Was Approved
When approving a sample, record what was approved, not simply "OK". If this is vague, a dispute during mass production is certain.
Items to finalise at approval:
- Sample number, date of production, revision number
- Colour (colour number or the result of comparison against the standard reference)
- Fragrance (result of comparison against the standard reference)
- Viscosity (numerical value with its measurement conditions)
- Model numbers of the container, pump and cap
- Plates for the label and carton (revision number)
- Fill volume and tolerance
The approved physical item is kept by both parties and used as the comparison baseline for mass production (the master sample / golden sample). The conditions for moving from sample approval to mass production are set out in OEM Sample Approval and Production Readiness.
6. Common Misconceptions
| Misconception | Reality |
|---|---|
| "If the sample is good, mass production will be the same" | Samples are sometimes made under near-handmade conditions. The equipment and the lot differ from mass production |
| "Once approved, the next order will be the same" | If the raw material lot changes, colour, fragrance and viscosity move |
| "The feel is good, so there is no problem" | Container compatibility and change over time cannot be known from feel |
| "Comparing viscosity values alone is enough" | Comparison is impossible if the measurement conditions differ |
| "Fragrance is a matter of preference" | Intensity, duration and alteration can be made into criteria |
7. Sample Evaluation Record Sheet (Minimum Configuration)
| Item | Recorded content | Judgement |
|---|---|---|
| Sample number / date of production | — | |
| Colour (comparison against standard reference) | Pass / revision required | |
| Fragrance (intensity, duration, alteration) | Pass / revision required | |
| Viscosity (measurement temperature, rotation speed) | Pass / revision required | |
| pH | Pass / revision required | |
| Discharge volume (specified number of strokes) | Pass / revision required | |
| Leakage (after inverted and on its side) | Pass / revision required | |
| Label adhesion | Pass / revision required | |
| Change over time (40°C / 5°C / room temperature) | Pass / revision required | |
| Overall judgement and revision instructions | Approve / re-prototype |
Frequently Asked Questions
Q. How many rounds does sample approval usually take? A. Where the evaluation items and pass/fail criteria are set first, most reach approval in one or two rounds. If the criteria stay vague, the number of rounds increases and the delivery date extends accordingly.
Q. Do we need to check change over time at the sample stage? A. We recommend at least 2–4 weeks of checking at high temperature, low temperature and room temperature. Separation and discolouration in particular cause large rework if they come to light after mass production.
Q. What should viscosity be based on? A. Rather than the numerical value itself, what matters is whether it matches the standard reference with the measurement conditions aligned. It is also partly determined by its relationship with the container's discharge volume.
Q. Can the sample and the mass-produced goods differ? A. The production equipment and the lot differ, so they will not be completely identical. It is important to agree that difference as a tolerance in advance and to keep the approved sample as the comparison baseline.
Q. We are concerned about the reproducibility of the fragrance. A. Fragrance materials are ingredients prone to lot-to-lot variation. We recommend defining the pass range by comparison against the standard reference, and checking again on repeat orders.
Summary
- A sample is judged on four layers — sensory, physical properties, compatibility and change over time — not on "feel"
- For sensory evaluation, decide the standard reference first. For physical properties, record the measurement conditions alongside the value
- Container compatibility (discharge volume, leakage, draw-up, label) can only be confirmed at the sample stage
- At approval, record what was approved by value and by plate revision, and keep the physical item with both parties
About the author
itsushou — China OEM & Product Development, GAMU Involved in product development, OEM production and factory coordination in China, publishing information on China OEM based on hands-on experience.
Related reading
- OEM Sample Approval and Production Readiness
- The Full Cosmetic OEM Process in China｜Formulation, Container, Packaging, Inspection
- Cosmetic Packaging Sourcing: Bottles, Pumps and Print
- China Pre-Shipment Inspection (PSI) Guide: AQL & Defect Remediation
- OEM & Product Development Support
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