# Induction Heat Sealing (IHS) Liners: Foil Thickness, Wattage, and Torque Compatibility
TL;DR — An induction heat seal (IHS) liner sits between two promises: the pack's opening behavior and the pack's seal integrity. Neither promise gets a published number — liner systems are configured per project; no induction liner is a recorded catalog component, and foil thickness and sealing wattage are project parameters, not published values. What the program does record is the verification context: cap/closure and gasket/seal as established components, the container families that wear them (59 lotion pumps, 19 trigger sprayers, 73 dropper bottles, 8 fragrance spray bottles), and torque, leakage, and vacuum testing as the capability-level hooks where compatibility is judged.
Why: The Liner Is a Configuration, Not a Component
Induction heat sealing is one of the quietest steps in packaging: an unseen foil circle becomes the barrier between the closure and the container mouth. Precisely because it is invisible, it attracts the boldest claims — "seals at any torque," "protects against tampering and evaporation" — from suppliers rather than from the record. This article draws the line where the record draws it:
- The liner is not a recorded component. The component entries that carry the closure-side sealing interfaces are cap/closure and gasket/seal; an induction liner is not among them. Liner systems are configured per project; no induction liner is a recorded catalog component.
- The process is real, the numbers are not published. The induction sequence — heating, foil delamination, heat-seal patching — is engineering common ground, but foil thickness, sealing wattage, frequency, and seal time are project parameters, not published values.
- The verification is a capability, not a recipe. Torque testing, leakage testing, and vacuum testing are recorded quality-program capabilities in the sealing family; their acceptance criteria are set per project.
- The population is recorded. The container families where a closure-plus-liner pairing is judged are 59 lotion pump models, 19 trigger sprayer models, 73 dropper models (glass and PET), and 8 fragrance spray bottle models (glass from an external partner), with neck finish windows from 18/410 to 28/410 on lotion pumps and 16/410 to 24/400 on droppers.
The practical consequence for a specifier is a discipline: treat every IHS parameter you are handed — foil thickness, wattage, frequency, dwell — as a project reference until the project record says otherwise, and judge the outcome through the program's verification hooks rather than through the marketing line.
How: Configuring a Liner Program Around the Record's Anchors
3.1 The induction sealing process, in outline
Induction heat sealing follows a recognizable sequence. The filled container is capped with a closure carrying a liner; the neck and closure crown pass through an induction coil; the alternating field couples with the foil layer and heats it; the foil delaminates from its backing board while the heat-seal patch bonds to the container rim; cooling sets the bond. From there the split is permanent — the patch stays with the container, the backing stays inside the closure — until the consumer's first opening breaks the bond.
Every variable in that sequence is a project variable. Foil thickness and sealing wattage are project parameters, not published values; so are the operating frequency band, the dwell under the coil, and the line speed. The record holds none of them. What the record does hold is the boundary: cap/closure and gasket/seal are the established component entries this configuration attaches to, and the configuration itself is per project.
3.2 Torque compatibility: the liner changes the opening behavior
A liner does not only seal; it changes how the closure behaves at the consumer's hand. The patch bond adds to the first-opening removal torque, the backing left in the closure alters the re-close feel, and a liner platform sitting proud of the rim can interfere with thread engagement. None of these is a free parameter — each is tuned against the neck finish, which is why the recorded finish windows matter: lotion pumps run 18/410–28/410 with the 20/415, 22/415, and 24/415 lines recorded among them, and dropper bottles run 16/410–24/400. A liner and its closure only mean anything on a finish the closure actually matches — the neck finish article covers the mechanical side of that contract.
The hook that captures the behavior is the torque test: a recorded quality-program capability with no published criteria, so the acceptance band — first-opening torque, sustained removal torque, re-close torque — is configured per project against the target consumer experience.
3.3 Seal verification: where leakage and vacuum testing come in
Once the patch is down, the seal story belongs to the assembled part, and the assembled part is judged by the program's leakage and vacuum testing capabilities — capability-level records in the sealing family, without fixed standard values. The discipline from the vacuum leak chamber article applies unchanged: an uncalibrated chamber produces confident verdicts with no meaning, so the baseline — reference leak, ramp, dwell — is re-established before any liner-sealed part variety is read.
The verdicts are what the final pack carries through transport and shelf life. A part whose patch holds under vacuum but whose closure backs off under vibration has a torque story, not a seal story — which is exactly why the torque check and the leak checks are deliberately paired rather than interchangeable.
3.4 Where the program stays silent
The record's silence is the point of this article. No induction liner is a recorded catalog component; no foil thickness, sealing wattage, frequency, or seal time is a published value; and no torque band or leak rate is a program standard. Every one of those numbers is a project deliverable — and the verification hooks that receive them are the recorded capabilities listed above.
<pre class="language-mermaid"><code>flowchart LR
A[Bottle + closure program<br/>lotion pumps 59 / trigger sprayers 19 / droppers 73] –> B[Liner system<br/>configured per project, not a catalog component]
B –> C[Induction sealing process<br/>foil thickness and wattage per project]
C –> D[Torque behavior check<br/>torque test, criteria per project]
D –> E[Seal verification<br/>leakage and vacuum testing]
E –> F{Judged against<br/>per-project criteria}
F –> G[Sealed pack released]
</code></pre>
What: Verified Program Data and the Verification Hooks
Two layers keep this article honest: what the program publishes, and what it deliberately does not.
- Component context: cap/closure and gasket/seal are the established component entries that carry the closure-side sealing interfaces an induction liner configuration would join.
- Boundary on components: no induction liner is a recorded catalog component — liner systems are configured per project.
- Parameter boundary: foil thickness and sealing wattage are project parameters, not published values; frequency band, seal time, and line speed are likewise project-owned.
- Container record: 59 lotion pump models, 19 trigger sprayer models, 73 dropper models (glass and PET), and 8 fragrance spray bottle models (glass from an external partner).
- Neck finish windows: lotion pumps 18/410–28/410 with the 20/415, 22/415, and 24/415 lines recorded among them; droppers 16/410–24/400.
- Verification hooks: torque testing, leakage testing, and vacuum testing are recorded capabilities in the quality program's sealing family — no method parameters are published, and acceptance criteria are configured per project and placed against the family records by the twelve-test matrix.
The hook that matters most is the last one: the appearance of seal, torque, and leak capabilities in the quality program is itself the recorded fact, and their numbers are deliberately not. Teams configuring an induction liner program should treat the capability record as the admission ticket and their own project validation as the seat.
Gotchas
- No liner in the record. No induction liner is a recorded catalog component; any liner spec is a project decision, and text presenting a liner platform as part of the catalog overstates the record.
- Foil thickness and wattage are not published. Any IHS number you are handed — foil thickness, wattage, frequency, seal time — is a project parameter until the project record says otherwise; the program records the capability, not the recipe.
- The liner shifts opening torque. A patch bond adds to first-opening removal torque and the left-behind backing changes the re-close feel; torque test criteria are configured per project, never borrowed from another program.
- Seal verdicts need the chamber discipline first. Leakage and vacuum testing judge the assembled closure, but only after the chamber baseline — reference leak, ramp, dwell — is re-established; see the vacuum leak chamber article for the order of operations.
- The neck finish is the mechanical anchor. A liner and its closure only work on a finish the closure actually matches; the recorded windows (lotion 18/410–28/410, dropper 16/410–24/400) are context for the pairing, not a guarantee from the record.
- Capability is not a standard. Torque, leakage, and vacuum are recorded capabilities without fixed values; presenting any threshold as "the program's standard" overstates the record.
Related Resources
- Categories: Bottles · Droppers · Pumps
- Related insights: Vacuum Leak Chamber Calibration · The 12-Test Lab Matrix · Neck Finish Compatibility
- Quality & Testing Capabilities — torque, leakage, and vacuum in the capability set