Induction and shrink

These are frequently discussed as alternatives and they do different things. In this category one of them is close to mandatory.

Two parts, two purposes

Induction bonds a foil membrane to the tub rim using heat generated by an electromagnetic field. It is a hermetic moisture barrier that also happens to be tamper evident.

Shrink is a plastic band heated to conform around the lid and neck. It is tamper evidence that contributes essentially nothing to barrier.

For a hygroscopic powder those are not comparable choices.

What induction needs to work

Four things, and missing any one produces a seal that looks right and is not.

A compatible liner with a foil layer and a heat-seal coating matched to your tub material. A flat clean rim, which means wiping every tub before capping, because powder on the land is the commonest cause of a failed bond. Correct torque on the lid, since the liner must be pressed against the rim. And the right dwell and power on the sealer.

Check a unit from every run by opening it. A partially bonded seal is invisible from outside.

Shrink and where it still helps

As a second layer of evidence, as a way of securing a lid that has to be removed and replaced frequently, and on formats an induction seal does not suit.

It is cheap and it is recognizable to customers, which has value even where it adds no protection.

Ordering it together

The tub, the lid, the liner and the sealer are one system. The liner is specified against the tub material and the lid, and the sealer's settings against the liner.

Buy a sample set and test the whole chain before committing to quantity, including opening sealed units after a week to confirm the bond held.

References