[Just mythoughts]

1) FOLLOW DIRECTIONS 2) Know what your elevation is, it makes a difference when you pressure can. (It's a temperature/pressure thing) 3) Make sure your jars, and especially the rim of the jars, are clean. 4) When in doubt refer to rule number 1.

I have canned for many years, and the absolute only way is to FOLLOW DIRECTIONS!!!!!

[Semperfiwife]

Those things scare me. My mother had one explode on her sending freshly snapped green beans all over our kitchen and the lid into the kitchen ceiling before returning to hit my mother. She recovered just fine. We found dried green beans in drawers and cabinets for a year after it happened.