A pre-shipment inspection of glass bottles should cover six areas: appearance and dimensions, physical performance, chemical safety, sealing, decoration and packaging. Bottles are sampled under an AQL plan, commonly critical 0, major 2.5 and minor 4.0 at General Inspection Level I. Pair the inspection report with batch-matched documents, because a load that arrives 3% cracked with closures that will not torque to spec is hard to pin on the supplier once it has left the plant.
Six areas the inspection report should cover
You do not have to run each test yourself. You do need to recognise a complete report when you see one.
| Area | What is checked |
|---|---|
| Appearance and dimensions | Bubbles, stones, cracks, scratches, mold marks and off-color glass; height, diameter, wall thickness and neck finish against the approved sample |
| Physical performance | Internal pressure (critical for carbonated products), impact, thermal shock and annealing stress. A poorly annealed bottle looks sound and then breaks in use. |
| Chemical safety | Hydrolytic resistance and, where required, heavy metal migration. Both are critical for food and pharma packaging. |
| Sealing | Screw-cap torque, leak tests and the fit between finish and closure |
| Decoration | Color accuracy, adhesion, placement and durability on printed, frosted or embossed bottles |
| Packaging | Cartons, layer pads, dividers, pallet wrapping and labeling, which are what protect glass inside a 40-foot container |
AQL sample sizes and accept/reject numbers
AQL, the Acceptable Quality Limit, is a sampling standard (ISO 2859 / ANSI/ASQ Z1.4). It lets an inspector examine part of a batch and reach a statistical decision on the whole order. At the common glass bottle setting given above, major defects are judged as follows.
| Batch size | Sample size | Major defects: accept / reject |
|---|---|---|
| 1,201 – 3,200 | 125 | ≤7 pass, ≥8 fail |
| 3,201 – 10,000 | 200 | ≤10 pass, ≥11 fail |
| 10,001 – 35,000 | 315 | ≤14 pass, ≥15 fail |
| 35,001 – 150,000 | 500 | ≤21 pass, ≥22 fail |
A single critical defect, meaning anything that could harm the user, fails the lot whatever the other counts are. Tables change with inspection level and client specification, so have the plant or the third-party inspector confirm the code letter and plan for your actual batch size.
Documents to request before the goods ship
Paperwork shows whether the inspection results are traceable. Ask for four things:
- Certificate of Analysis (CoA) stating batch number, tests performed, methods, results and who approved it.
- Test reports for the physical and chemical tests: internal pressure, thermal shock, hydrolytic resistance and migration.
- Dimension reports giving measured values against the approved sample, not just pass/fail summaries.
- Packaging and loading photos, or a pre-shipment report from the plant or a third party.
The batch number on the CoA must match the one on your cartons. If it does not, the document proves nothing about your load. Our analysis of common glass bottle defects describes the flaw types inspectors look for.
When one inspection is not enough
Some faults arise after forming, during decoration, packing or container loading, and others are cheaper to stop before they repeat. Importers therefore inspect at up to three stages:
- Pre-production: confirm mold samples, material and specifications before the run begins.
- During production: check the line and random bottles while the order is being made.
- Pre-shipment: a final random inspection after finishing, decoration and packing.
If the budget covers only one, choose pre-shipment. For custom bottles or a full container, the first two stages guard against rework.
Handling a failed inspection
A failure starts the correction; it does not end the order. Work through it in sequence:
- Sort the findings into critical, major and minor. Critical stops the shipment, major means rework or replacement, and minor within tolerance may pass under your AQL.
- Obtain the corrective action in writing: root cause, rework plan and re-inspection date.
- Re-inspect after the fix. A verbal assurance is not enough.
- If the cause is systemic, escalate by requesting new samples, bringing in a third-party inspector or revisiting the specification.
Raise the inspection schedule with the plant's QC contact early; a plant that volunteers the details is a good sign. Supplement and pharma buyers should verify credentials first, using our guide to checking cGMP certificates, and the supplier checklist covers the remaining points.