I was reading an article on a blog "LIVING HOMEGROWN" & found this info.,I wanted to share & see if others have any thoughts! It may have been covered here prior!
This is what I C&P below as posted on the Blog!
I’m sure you are familiar with the standard 2-piece canning jar lids. The flat lid sits on top of the jar and the ring tightens around it holding the lid in place as you process the jar in either a water bath or pressure canner. Most canners use this type of canning lid.
But did you know that it is considered unsafe to leave the ring on a canning jar AFTER it has been processed?
Sometimes when I mention this to people, I get a deer-in-the-headlights response. I think part of the problem is that few canning books even mention this. Also, most photographs of canned foods show the rings on the jar. Heck, I’m guilty of this myself! I like to photograph the jars while they are cooling (and the rings are on). I guess I am just excited and don’t want to wait for them to completely cool. But doing this gives the illusion that they are being stored that way.
Important: Now, let me be clear. The rings DO need to stay on the jars while the jars are cooling down after processing. They should only be removed after the jars have reached room temperature.
The main purpose of that ring is to align the lid properly on the jar and to hold it in place while the vacuum seal forms. After that, it has served its purpose.
Three Things Can Happen If You Don’t Remove the Rings
You can get:
1) A False Seal: The ring can inadvertently hold a lid on a jar that has a broken seal. In other words, if the vacuum seal is compromised, that ring will make it LOOK like it is okay even if not sealed. Then later, when you pull that jar off the shelf and open it, you may or may NOT be sure if it was already open or not. And depending upon how long that jar has been unsealed, you may not notice that the food is going bad.
2) Rust: Leaving the ring on can lead to rusting of the ring. Have you ever left a ring on and then later had trouble twisting it off because of rust? I have. Then as you wiggle and fight with the ring, you can break the seal on the jar…or was the seal already broken? Hmmm…Reason number one comes back to bite us again. We don’t know if we “just” broke the seal or it has been open for a week or more.
3) Mold: Yes, mold can grow under the ring and that can lead to the vacuum seal being lost. This happens because food sometimes siphons out of the jar during processing and gets trapped under the ring. As it sits, it begins to mold and that mold grows and can push on the edge of lid and break the seal. In fact, after your jars are completely cooled, you should remove the rings AND wipe down the jars to remove any stick residue. Then label the jars and sit them on the shelf.