Sealing and shrink

A seal can be a barrier, evidence of tampering, or both, and the three are usually discussed as one thing.

Two different promises

A barrier keeps moisture, oxygen and aroma out and the product's own volatiles in. Tamper evidence tells a buyer the jar has not been opened since it left you. They are separate requirements, and a closure can offer one without the other.

A lined cap is a barrier and no evidence. A shrink band is evidence and almost no barrier.

Induction, and what it costs

An induction seal bonds a foil membrane to the jar land, giving a genuine hermetic barrier and visible evidence in one part. For a product whose enemies are moisture and air, it is the strongest available answer.

It needs a sealing unit, compatible closures with an induction liner, and a jar with a clean flat land. It is a real capital step rather than a consumable change, and the jar rim must be brushed clean before capping or the seal simply will not take.

Shrink bands

Cheap, universal and visible. They need a heat source, they suit any closure, and wholesale buyers recognize them without explanation.

They do nothing for moisture. A banded jar with a foam-lined cap is a jar that looks sealed and breathes.

Which you actually need

For a fast-turning line sold face to face, a good liner and no band is defensible and most small producers stop there.

For anything sold online into a cupboard, or slow moving, or priced where a dull jar is a reputational problem, induction earns its cost. For wholesale, expect to be asked for tamper evidence by name whatever the retail customer thinks.

Decide before ordering jars, because the choice constrains the closure and therefore the finish.

References