Liner construction
Material, thickness, facing and any barrier function are selected for the closure and product. Use the supplier’s identified specification.
Closure sealing system
ROPP cap liners, compression and finished-bottle seal performance.
The liner and bottle sealing surface create the pack seal while the formed thread and pilfer band control retention and opening. The correct compression and test method depend on the selected closure system, bottle and product.
Seal principle
Review liner, bottle and product as one system.
A ROPP closure does not seal because the aluminium thread looks sharp. The liner or sealing element must contact the intended bottle surface under the conditions defined by the closure system. Bottle finish geometry, damage, contamination, cap seating, top pressure and liner construction can all affect the result.
Use the closure supplier’s approved cap and liner combination. Do not substitute liner materials or assume one setting transfers between products without review. Filled-pack trials are important where product residue, pressure, temperature or storage orientation can change the seal condition.
Seal evidence to collect
- Closure and liner supplier reference
- Bottle finish and sealing-surface drawing
- Product and fill condition at capping
- Neck-cleaning or drip-control method
- Cap height or compression measure where specified
- Opening and leak/pressure test method
- Conditioning, storage and retest interval
- Good and failed retained samples
Seal variables
Four interfaces govern the finished closure.
Bottle sealing surface
The contact land must be dimensionally suitable, clean and free from chips or damage that interrupt liner contact.
Compression and seating
The cap must arrive squarely and be seated by the correct head condition before thread and band forming are accepted.
Product and storage
Fill temperature, internal pressure, product residues, transport and storage orientation can affect the relevant test plan.
Leak investigation
Do not correct every leak by increasing head pressure.
Excessive force can damage the shell, liner, insert or bottle. Isolate the evidence first.
| Check | What it can reveal | Controlled action |
|---|---|---|
| Incoming bottle finish | Damage, out-of-round condition, incorrect finish or contaminated sealing land. | Compare with approved drawing and clean retained reference bottles. |
| Incoming closure and liner | Wrong liner, displaced insert, shell damage or packaging-lot change. | Identify the lot and compare uncapped samples with approved stock. |
| Cap seating and height | Skewed placement, insufficient or excessive compression, inconsistent support. | Reset from a controlled first-off procedure and verify across heads. |
| Thread and band formation | Off-centre bottle, roller interference or tooling mismatch. | Review head alignment and compare the affected station with an approved one. |
| Test method | Inconsistent conditioning, fill, temperature, dwell or result interpretation. | Repeat by the documented method using traceable samples. |
Authoritative references
Use the data sheet for the actual closure system.
CETIE publishes cap and finish data sheets for several aluminium screw-closure and glass-finish systems, together with bottling guides and pressure-resistance test references. For wine, a named closure system may combine a specific aluminium cap, bottle finish, liner and application condition. The exact supplier system—not a generic website description—controls the final choice.
CETIE cap data sheets · CETIE finish data sheets · CETIE test recommendations
Trial planning
Prove the seal under representative filled-pack conditions.
Approve incoming components
Identify the bottle, cap and liner lots and compare them with the selected supplier references.
Establish a clean dry first-off
Set bottle support, cap placement and forming condition without product contamination obscuring the result.
Run the filled-pack condition
Use the intended product or approved trial equivalent and reproduce the relevant neck, fill, temperature and handling condition.
Condition and test consistently
Follow the agreed time, orientation, opening and leak/pressure method. Record raw results and sample identity.
Retain approved evidence
Keep labelled samples, settings and lot references so later changes can be compared with the approved pack.
Buyer questions
ROPP liner and seal questions.
Can the machine supplier choose the liner?
The closure and liner specification should be agreed with the closure supplier and packaging owner for the product and bottle. The machine trial then confirms application.
Does higher compression always improve the seal?
No. Excessive compression can damage components or distort the closure. Use the approved setting and finished-pack tests.
Why test filled bottles?
Product residues, fill temperature, internal pressure and storage can introduce conditions that a dry sample does not reproduce.
Can a cap pass opening tests but still leak?
Yes. Opening performance and seal integrity are related evidence but not interchangeable. Use the complete quality plan.
What if the bottle finish is damaged?
Segregate the bottle and investigate the supply condition. Machine adjustment should not be used to compensate blindly for an out-of-spec sealing surface.
Review the liner, bottle finish and product together.
Send closure and bottle drawings, filled samples, current leak evidence and the test method your pack must pass.