Same with glass topped stoves, etc. All of this glass is a specially treated soda-lime glass. One way to do it is to replace some of the sodium with potassium. There may be other methods now. The result is a kind of case hardening, which -in the case of glass- places the entire object under enormous internal stress. It thus resists bangs and bumps, until an external stress overcomes the internal force, usually by being applied to a very small area. When that happens, the entire object explodes from internal forces. However- the explosion is "safe", in the sense that it creates lots of small, not very sharp pieces, rather than a few big flying knife edges. Look up Prince Rupert's Drops (which are easy to make at home if you have some regular glass and a torch).
Heat can act as a localized stressor, too.
This is what happened to Pyrex brand glassware. It's no longer low expansion borosilicate glass (expensive). It's treated soda lime glass. The label now says "Pyrex Brand", not "Pyrex"- because "Pyrex" has a specific meaning, and the kitchen stuff isn't that (lab glassware is).
I set hot pizza on a glass table years ago and it popped. Never owned another after that, fuck a glass table top.
ReplyDeleteSame with glass topped stoves, etc. All of this glass is a specially treated soda-lime glass. One way to do it is to replace some of the sodium with potassium. There may be other methods now. The result is a kind of case hardening, which -in the case of glass- places the entire object under enormous internal stress. It thus resists bangs and bumps, until an external stress overcomes the internal force, usually by being applied to a very small area. When that happens, the entire object explodes from internal forces. However- the explosion is "safe", in the sense that it creates lots of small, not very sharp pieces, rather than a few big flying knife edges. Look up Prince Rupert's Drops (which are easy to make at home if you have some regular glass and a torch).
ReplyDeleteHeat can act as a localized stressor, too.
This is what happened to Pyrex brand glassware. It's no longer low expansion borosilicate glass (expensive). It's treated soda lime glass. The label now says "Pyrex Brand", not "Pyrex"- because "Pyrex" has a specific meaning, and the kitchen stuff isn't that (lab glassware is).
Poorly Tempered glass and thermal shock
ReplyDelete