Mash wrote:That's a bit harsh Myles. What's wrong with licking batteries!

Yeh! It used to be a bet when we are at school.
Anyway back to glass - in the right setting, with the right gear - think a laboratory setup - then sure you can do it.
I have broken preserving jar thumpers twice.
Once was due to a water drip from a leaking coolant line hitting a hot jar, just an oversight on my part.
The second time I thought I had everything sorted but the bottom of the jar just split off. I have no proof but i think it was the cavitation caused by the collapsing bubbles. Probably some flaw in the glass.
Nearly had a heart attack when that ended up on the floor.