Sealing and shrink

Closing a skincare container involves three separate components and people frequently buy one and assume they have all three.

Three parts doing three jobs

The closure holds the pack shut. The liner seals it against moisture, oxygen and loss. The band or membrane shows whether it has been opened. Three jobs; a plain cap does only the first.

The liner is the barrier

This is the component that decides whether your product equilibrates with a bathroom over a year. A foam liner is a gasket that stops leaks; a proper barrier liner or an induction membrane is a different proposition.

It is also a compatibility question. The liner sits against the formula for the product's whole life, and low pH products and some solvents will degrade an inappropriate one. Liner material is a published specification and it belongs in the compatibility study.

Shrink and its limits

A shrink band is cheap, universal, recognizable and adds essentially nothing to barrier performance. A banded jar with a foam liner is a jar that looks sealed and breathes.

It needs a heat source and a little practice, and on small curved containers it takes some trial to get a band that sits straight and does not distort the label beneath it.

Putting it together

Match the closure to the container's neck finish, written as two numbers such as 20-410: the diameter in millimeters and the thread profile. Specify the liner deliberately rather than taking whatever ships. Decide on induction or band before ordering, because induction constrains both closure and container.

And wipe the land before capping. Product on the rim is the commonest cause of a seal that fails, an induction bond that does not take, and a customer receiving a leaking parcel.

References