You’ve got the bottle. You’ve got the cap. You’re ready to go.
Then someone asks:
“What liner are you using?”
The little round thing inside the cap? Yep. That thing.
It might not be the most exciting part of your packaging, but liners have more going on than meets the eye. They can help with sealing, leaks, product protection and giving your packaging a more professional finish.
The catch? Not all liners work the same way.
So, let’s get this sealed.
Pressure-Sensitive Liners: Just Add Pressure
The name gives this one away.
A pressure-sensitive liner sits inside the cap and uses the pressure created when you tighten the cap to form a seal against the container opening.
No heat. No induction machine. Just a little pressure.
Once the cap is screwed on firmly, the adhesive side of the liner presses against the rim of the container. Give it some time to bond and, when the cap is removed, the liner should stay behind on the container.
Important: Don’t screw the cap on and immediately remove it to see if it worked. Give the liner a chance to do its thing. Nobody performs well under that kind of pressure.
For our 83 mm cap, we use both an 83 mm EPE liner and an 83 mm pressure-sensitive liner. The EPE liner goes into the cap first, followed by the pressure-sensitive liner. Together, they add thickness and help create an even spread of pressure across the container opening for a more consistent seal.
EPE Liners: The One That Stays Put
An EPE liner is a soft, foam-like disc that stays inside the cap. As you tighten the cap, it compresses against the rim of the container, creating a snug fit and a barrier between your product and the cap.
Unlike a pressure-sensitive liner, it does not stick to the container opening.
So if you open your cap and the EPE liner is still sitting inside it, don’t panic.
It hasn’t failed. It’s exactly where it wants to be.
Heat-Induction Liners: Things Are Heating Up
Ever opened a product and found a foil seal over the bottle opening?
That’s where heat induction comes in.
A heat-induction liner sits inside the cap, but tightening the cap alone won’t seal it. The capped container needs to be used with an induction sealing machine.
The machine heats the foil layer of the liner, allowing it to bond to the rim of the container.
When the customer removes the cap, the foil seal stays behind.
It’s a great option when you want a more secure, tamper-evident and professional finish.
Just remember: heat-induction liners need the right equipment and need to be compatible with your container.
So… Which Liner Does What?
| Pressure-Sensitive | EPE | Heat Induction | |
|---|---|---|---|
| Sticks to container? | Yes | No | Yes |
| Stays inside cap? | No | Yes | No |
| Needs a machine? | No | No | Yes |
| How does it work? | Pressure + adhesive | Compression | Induction heat |
Easy enough, right?
A Few Liner Plot Twists
“My EPE liner didn't stick!”
Good. It isn’t supposed to.
“My pressure-sensitive liner didn't stick immediately!”
Give it some time to bond before removing the cap.
“Can I use a heat-induction liner without an induction sealer?”
Unfortunately, no. This is one problem that cannot be solved with a hairdryer and determination.
“If it’s 83 mm, will it fit any 83 mm container?”
Not necessarily. The cap, liner, container opening, container material and product all need to work together.
Small Disc. Big Responsibility.
A liner might be one of the smallest parts of your packaging, but choosing the right one can make a big difference.
So next time you see that little disc inside your cap, give it some credit.
It’s under a lot of pressure.