Last updated: 30 August 2026.
Quick answer: Before a bottle ships, three physical tests catch the failures buyers actually experience: a leak test on the closure seal, a drop test on the filled and sealed bottle, and a capacity check that the bottle holds its declared volume. These sit on top of dimensional, gram-weight and torque checks, and together they are what a credible pre-shipment inspection report should contain.
Why “it looks right” is not a quality check
Most packaging failures are not visible in a photograph. A bottle can have perfect colour and dimensions and still leak from a cap, shatter from waist height, or hold 12% less than the label promises. Those failures only appear under load — which is exactly what the three tests below simulate.
A supplier who can only describe the bottle but cannot produce a QC report with pass limits is describing a product they have not actually tested. The report, not the sample, is the deliverable.
The three tests, and what each one catches
| Test | What it catches | How it is done |
|---|---|---|
| Leak / closure seal | A cap or pump that does not seal, a thread mismatch | Fill, apply the closure at specified torque, invert or pressurise, check for leakage |
| Drop impact | Weak walls, thin corners, poor material distribution | Drop a filled, sealed bottle from a set height onto a hard surface, check for crack or burst |
| Capacity / fill volume | A bottle that under-fills, or overflows on the line | Fill to brim (and to the declared fill level) and measure the volume |
The leak test is the most consequential because a leaking closure turns an entire batch into a complaint, and it usually traces back to the neck finish or the closure torque rather than the bottle body.
The supporting checks you should see in the report
The three headline tests are not enough on their own. A complete first-article or pre-shipment report also includes:
- Dimensional check — height, diameter, wall thickness, and the neck finish dimensions against the drawing, within a stated tolerance (commonly ± 0.2 mm to ± 0.5 mm depending on the feature).
- Gram weight — the honest cost and structural indicator, checked to a tolerance such as ± 1 g.
- Closure torque — the force to open and close, measured so the cap is neither too loose nor impossible to remove.
- Compatibility soak — your actual formula in the actual bottle at elevated temperature for 2-4 weeks, to catch separation, discolouration or stress-cracking that only appears over time.
The compatibility soak is the test most brands skip and most later regret, because it costs weeks and a bottle of formula, and it catches failures that no dimension check can.
How sampling and standards make the report trustworthy
Testing a single bottle tells you almost nothing. Credible factories test on a sampling plan, not a hand-picked sample, and they test against a declared standard rather than a vague “good”.
- AQL sampling (Acceptance Quality Limit, described in ISO 2859-1) defines how many pieces to inspect for a given batch size and the defect level you will accept. Ask for the AQL level, not just “we inspected 20 pieces”.
- Transit testing against the International Safe Transit Association (ISTA) standards covers drop, vibration and compression on a packaged unit — the failure mode that appears after 35 days at sea, not on day one in the factory.
- Quality management under ISO 9001:2015 is what makes all of the above repeatable across production runs rather than a one-off demonstration.
A report that names a standard and a sampling plan is evidence. A report that says “passed inspection” is a tick in a box.
What to ask for before you pay the balance
Turn the concepts above into a short, concrete request list:
- A pre-shipment inspection report with pass/fail limits for leak, drop and capacity.
- The AQL level and sampling plan used for your batch size.
- The torque and gram-weight values with tolerances, in writing.
- A compatibility report for your specific formula, if it is chemically active.
- A retained reference sample on both sides, so future re-orders can be compared against the approved standard.
If the supplier can produce all five without hesitation, the risk in your order has already been measured. If any one of them produces an evasion, the risk has just been discovered.
Frequently asked questions
What is a drop test for a bottle?
A drop test drops a filled, sealed bottle from a set height onto a hard surface to check that it does not crack, shatter or leak. Heights and pass criteria follow a declared standard such as an ISTA procedure.
What does “capacity” mean on a bottle?
Capacity is the volume the bottle holds, usually stated both brimful (to the very top) and as a fill level. A bottle labelled 250 ml should hold a usable fill volume close to 250 ml with headspace, not merely brim to 250 ml.
Why do bottles leak even when the cap fits?
Common causes are a neck finish slightly out of tolerance, a closure applied at the wrong torque, or a liner that does not match the seal surface. The leak test exists to catch these before they reach a customer.
What is AQL in bottle inspection?
AQL (Acceptance Quality Limit) is a sampling standard, defined in ISO 2859-1, that specifies how many pieces to inspect for a given batch size and the maximum acceptable defect level. It makes inspection repeatable instead of ad hoc.
Should I test the bottle with my actual product?
Yes. A compatibility soak test — your formula in the bottle at elevated temperature for 2-4 weeks — catches separation, discolouration and stress-cracking that no dimensional or drop test can reveal.
What is the difference between a leak test and a drop test?
A leak test checks the closure seal under static load (inversion or pressure); a drop test checks the structural integrity of the filled, sealed bottle under impact. A bottle can pass one and fail the other.
Next step
If you are at the inspection stage with a packaging supplier, send us the QC requirements your buyer or retailer has asked for and we will tell you which tests and standards apply to your bottle — and how our own pre-shipment reports measure up.
Shijin Packaging — factory-direct cosmetic and daily-chemical plastic bottles since 2003, operating 30+ automatic blow-molding lines and 10+ injection-molding machines across a 15,000 m² facility in Huizhou, Guangdong, with daily capacity of approximately 200,000 pieces.
- Website: https://shijinpackaging.com
- Full catalogue: https://shijinpackaging.com/catalog/
- Email: sales@shijinpackaging.com