Hey All, In my non-smoking life I'm a chemist. I've worked with tons of glasswear under positive pressure and vacuum and am not in the least concerned using mason jars with a foodsaver - and I use it on pickles myself. That said, always inspect the jars carefully for cracks, chips, etc. and don't use if you find any - keep for non-heated, non-vac use (or toss, they don't cost that much). I do recommend wearing safety glasses - when glass fails it's not pretty. I place my jars in a small cooler while I pull the vac as a safety shield and to catch the mess if it does pop. Oh, the outside pressure is irrelevant ;) the in water test was likely to contain the shards if it did fail or they were doing a version of a hydrostatic test like is done on compressed gas cylinders.
