The 15-minute room-temperature test
The band functionality test is simple and has a strict rule: samples must sit exposed for 15 minutes at room temperature before evaluation. This time allows the material to settle and eliminates false positives from caps that just came off the line. Before anything else, rule out obvious physical defects: a cap with a broken band, smiley band or missing band does not even reach the functionality test stage.
Tabs flattened against the inner diameter: the cap was not well applied — or the height of the lock ring (bottle) is out of spec.
Band changes orientation but does not separate: manufacturing defect of cap or bottle. Capper adjustment will not solve it.
Causes — Cap
| Item | Cause | Solution |
|---|---|---|
| 13.1.1 | Missing horizontal cut on the cap. | Change the lot and engage supplier technical support. Without the cut, the band does not separate by physical principle — no equipment can correct it. |
| 13.1.2 | Excessively firm band (high pull test). | Send cap samples for pull-test analysis. Pull test above the window keeps the band intact after threading — function inverted. |
pull-test-laboratorio.jpeg
Cause — Bottle
| Item | Cause | Solution |
|---|---|---|
| 13.2.1 | Lock (or interference) ring of the bottle finish out of spec. | Verify with a finish gauge the diameter and height of the ring. Discard defective samples from stock. |
Causes — Capper (cross-reference)
When the defect is not in cap or bottle, the root cause is always one of the two most common guide items:
| Item | Cause | Solution |
|---|---|---|
| 13.3.1 | Under-applied cap. | See under-application diagnosis. Band only works when the cap is fully seated. |
| 13.3.2 | High cap. | See high cap diagnosis. Without seating, the lock ring does not engage the band. |
Next step
A non-functioning band is the defect that does not show up immediately — it manifests when the consumer opens the package and realizes it could have been tampered with. That is why quality control in packaging must include the 15-minute test as routine, not exception. To deepen the control, the cap application angle measurement procedure (next post) is the most useful complementary tool.
Guide to Cap Application Problems
The 13 most common capper failures — diagnosis, root cause and correction. Free technical material.
Download the full guide →