Tamper evidence

What the vacuum already gives you

A properly sealed two-piece lid is already tamper evident and most buyers know it, which is why this question comes up less often than people expect. The button is the evidence and it cannot be restored once broken.

A lid that has sealed is drawn down and does not move when pressed. A lid that has been opened does not go back to that state. For a direct sale that is usually enough, and it is the reason market jam is not routinely sleeved.

When a sleeve is worth it

There are situations where the vacuum is not enough, and they are about the channel rather than about the product. Knowing which ones saves adding a cost to every jar for the sake of a few.

• Retail shelves, where a jar is handled by people who are not buying it.
• Wholesale accounts that ask for it as a condition.
• Shipping, where a band also keeps the band on.

What it costs

A heat gun, the sleeves, and a step per jar at the end of a long day. At market volumes that step is often the one that makes a batch finish an hour later, which is a real cost on a product with thin margins.

What it does not do

A sleeve is evidence rather than protection, and conflating the two is how it ends up treated as a substitute for something it does not replace. A sleeve on a jar that did not seal is worse than nothing, because it looks like assurance.

It does not make an unsealed jar safe and it does not extend shelf life. If the vacuum did not form, a sleeve hides that rather than fixing it, which is the argument for checking seals before anything else goes on the jar.

References