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Why is it that Jars have the tamper-evident safety button that pops up when the seal is broken, but cans don't have it?
Sauces, jellies, baby food, and all sorts of wet food in glass jars utilize a springy indicator "button" in the middle of the lid that changes shape when the internal vacuum is lost. canned food is also supposed to be kept under a partial vacuum, so why don't cans have the little pop-up button?
In case you don't know what I'm talking about, Wikipedia describes it well in this exerpt:
https://en.wikipedia.org/wiki/Tamper-evident_techn...
"Jars of food items soon started appearing with a metal bubble-top lid, commonly known as a "safety button", which—like the lid of a Mason jar—popped out if the jar had ever been opened and stayed flat if the jar was in pristine condition. Customers were advised to never buy a product with a popped lid. (These lids would also pop out if the jar was contaminated by gas-producing bacteria, which was an additional safety feature.) Presumably the seal was achieved by packaging the jars in a low-pressure atmosphere, although companies were reluctant to divulge details.
Newer jars of food tend to come with a plastic wrap around the edge of the lid, which is removed when opening, although the springy-cap designs are still in common use. "
What I really like about the jar buttons is that they exist in a binary state; they are either pushed in by atmospheric pressure or they are popped out due to the lack of a seal, and it is easy for the consumer (me) to determine their state with a finger click. So, really, would it cost too much to stamp a button into can lids? I dislike having to guess whether the can lid seems like it is tight enough, and whether it is really sucked down enough or not.
Libby's, Dole, DelMonte, Goya, Campbell's, Progresso, and Dinty Moore, none of these guys have a pop-up button on the lid.
Sure you might be able to cite some can that comes out of Singapore, Denmark or somewhere, but the vast bulk of canned goods in the USA (and the rest of the Americas) don't have the pop-up "Safety Button" and I've got to wonder why.
Okay, for some unfathomable reason I'm encountering a good bit of hostility. Let me be clear, I'm not talking about someone in the store popping the pull tab on that kind of can for a quick sip in the store, or a lookie-loo, or somebody walking through the store with a can opener in their pocket--or even randomly stabbing cans with an icepick, I'm talking about a pinhole leak caused by rough handling in the warehouse. (something you don't ordinarily find out about for months)
5 Answers
- CrustyCurmudgeonLv 79 months ago
The center of the lid is indicative of the vacuum or pressure in a sealed tin can. If it bulges upward, toss it and don't even open it. If it still dips down, it should be safe (not necessarily tasty, but bacteria free).
- sunshine_melLv 79 months ago
A can is either open or it's not. Holes are visible if the container's been breached.
A jar can look sealed but have been opened already.
- Fred3663Lv 79 months ago
It would be evident if someone had opened a can to tamper with the contents, they wouldn't be able to make the can look untouched.
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