Leakage around a closure: investigating the root cause with the right samples

What should you record before opening a leaking package, which components should stay together, and which question should guide the test method?

2026-10-01

Representative illustration of a bottle neck, closure, droplet and magnifier for a leakage investigation. — Representative illustration; not a photograph of an actual Peksan product, production area or test.

1. Record the first findings before changing them

A wet bottle in a case does not, by itself, show that the closure has failed. Liquid can travel from its exit point to another surface. An effective investigation considers the failed package, comparison samples and filling records together. The aim is to establish which variable accompanies the problem, as well as to reproduce it.

Opening, retightening or wiping a leaking package immediately can alter the evidence. First photograph its position, the wet area and the closure. Record the filling date, closure and bottle batches, line and capping head where these details are available. Note whether the problem appeared immediately after filling, during storage or after shipment.

Segregate the sample under your site’s safe handling procedures without contaminating other packages. Do not turn the original package into a reclosed trial sample. If it must be opened for investigation, record who opened it, when and why. Keep the closure, bottle and any liner or foil associated with the same sample.

2. Examine three areas as separate possibilities

Consider damage to the bottle body and base, the neck and finish, and the closure’s sealing contact separately. External wetness alone does not establish the leakage path. Record observations such as a cross-seated closure, contamination or damage at the sealing surface, or displacement of a liner where present. Treat these as findings to investigate, supported by photographs and sample identification, rather than proven causes.

For example, wetness around the neck does not immediately justify changing the closure. A bottle-body issue in the same batch, or liquid deposited on the outside during filling, also deserves investigation. Do not assume a particular sealing mechanism before checking the design and package construction.

3. Build the comparison with traceable samples

Where possible, set aside unopened packages from the same production that show no leakage, plus unused closures and bottles, under separate sample identifiers. Record conditions including the filled product, fill level, capping setting, elapsed time, temperature and transport history. Using an unrelated bottle as the reference makes it difficult to identify which variable caused a difference.

Comparing one variable at a time in separate trial samples can narrow the investigation. However, removing a used closure and fitting it to another bottle is not equivalent to the original closure application. Identify any such trial as reassembly. A limited number of satisfactory results does not approve the whole batch or every use condition.

4. Choose the test for the failure you need to investigate

Start the test plan with a question: is a filled package leaking liquid under distribution conditions, or is an empty rigid container resisting differential pressure? ASTM D5094/D5094M-24 addresses qualitative assessment of gross liquid leakage in rigid and semi-rigid containers up to 4 L with threaded or lug-style closures.

ASTM D4991-25 concerns the leakage resistance of empty rigid containers under differential pressure. It therefore does not directly establish filled-product shelf life or performance under every use condition. Agree a method suited to the package construction, and the full procedure of the current standard, with the laboratory. Do not treat results from different methods as equivalent.

5. Define acceptance conditions before testing

Document sample number and selection, conditioning, package orientation, test duration, applied load or differential pressure, the definition of leakage and acceptance criteria before testing begins. The customer, packaging suppliers and laboratory should agree these around actual use and distribution conditions. This article does not propose a universal pressure, temperature, duration or torque limit.

The report should identify the tested combination and conditions instead of simply stating “passed”; keep observations, measurements and interpretations separate. No leakage under one method does not guarantee the same result under another method or with a different filled product.

6. Send the supplier a file that supports a decision

Include the product code, closure and bottle batches, bottle-finish drawing revision, relevant technical datasheet, filling and capping conditions, photographs of the first findings and a sample list. Record trial changes and their outcomes chronologically. This turns “the closure leaks” into an investigation in which everyone can assess the same evidence.

7. Verify the correction against the original problem

Check the proposed change using traceable new samples under conditions representative of the original problem. If results are satisfactory, record the specific combination and conditions accepted; do not automatically extend that acceptance to another bottle, closure or filled product. Use the relevant product code when requesting samples or a technical assessment from Peksan. For example, a request concerning 038.016CTP10L should include the bottle and application details: the code alone does not establish compatibility or approve leak resistance.