Why Canning Jars Break

How disappointing, Amy! Sometimes jars have a flaw and they just break, and other times it's what your friends mentioned about hot/cold, cold/hot.

I had that happen with one jar of peach jam several years ago. It was a spanky new jar into cold water, and not the first cold packing of that batch either, so I doubt it was temperature shock. I chalked it up to not being on the family shopping trip that acquired the jars in the first place. I had told them what to get, but they decided to save money (a dollar or two at most!) and bought a cheaper flat. So I am figuring a flaw in the glass is what did it in. I just count myself as lucky that it cracked around instead of bursting, which would have broken more jars in the batch.

I have been doing a lot of canning here recently. I had some brand new jars break on me while I was canning some beef stew. I cold packed everything and had cold water in the canner. I totally believe that some jars are just weak from the get go. I have had some previously used jars do the same thing and I understood that but brand new... I was in shock. I'm glad you posted this because I now know it was just weak jars!