Eli5, why do Mason jar lids typically come in 2 parts, threads and seal, as opposed to nearly every other commonly used household container?

Question

Eli5, why do Mason jar lids typically come in 2 parts, threads and seal, as opposed to nearly every other commonly used household container?

In: 7899

Answer 1

The Mason jar has three parts: the jar, the lid, and the ring. They are made for preserving food by canning. That process seals the lid to the jar very tightly (there’s a little plastic seal on the lid, and a vacuum in the jar that holds it tightly in place). The ring is there to protect the lid and make sure the seal doesn’t break and to hold the lid after your break the seal to open the jar.

Popping the lid off requires using something (I use the edge of a spoon) to pry up the edge of the lid to break the seal. Doing this can damage the seal material, nick the lid’s metal, or bend the lid — all things that would make it unsafe to use for canning again (microorganisms can sneak in). However, the rings and jars can be reused many times over.

So, the lids are sold separately because they aren’t safe to use over and over, whereas the rings and jars can be reused for years.