Material fitted inside a closure; an induction liner includes a foil and a heat-seal layer for bonding to the container.
Also called: closure liner; induction liner; innerseal.
Is every cap liner an induction seal?
No. A cap liner is a component inside a closure. Non-induction liners can use materials such as foam; an induction heat-seal liner includes foil and a compatible layer that bonds to the container. The construction determines the sealing function.
Ask for the liner family and construction instead of ordering only a cap size or “foil liner.” Identify the container-contact face, bottle material and intended opening action. The sealing layer and the support/backing perform different jobs; the cap itself is another component.
What stays in the cap after a two-piece liner is sealed?
In a wax-bonded two-piece construction, heating separates the foil seal from a backing that remains in the cap. That backing can serve after the original foil is opened. A one-piece liner can still be a laminate; one-piece does not mean one bare material layer.
Specify what remains on the bottle and in the cap after sealing and first opening. Wax separation describes one two-piece construction; other liner technologies can behave differently.
Can the right cap size compensate for the wrong liner?
No. Material compatibility and mechanical fit are separate questions. Check the container-facing sealing layer, liner rigidity, overhang and interference as well as the cap/bottle fit. Retain the exact liner code and package drawings when assessing a sample.
Assess the bond, barrier performance and opening behaviour on the actual package. A printed message on the liner does not establish these properties or its tamper-evidence function.