I've also used mayonnaise and spaghetti sauce jars for canning and I pressure can everything as well, never had a break. That being said, I have noticed two things in the last couple of years. One, the glass isn't as heavy as in previous years. Second, the rings don't fit on most of the newer mayo and spaghetti sauce jars. I think this is to discourage people from using them in the canning process. Since I noticed the thinner glass, I haven't tried the "new" mayo jars.