rad14701 wrote:While mason jars are reqularly simmered in a boiler prior to lidding as part of the canning process I would also be a bit leary of having one filled with hot ethanol dangling in close proximity to an open flame... I know it's been done, but...
i blow glass as a hobby...
the key thing with glass is thermal shock.
all materials expand when they heat up. glass however, is an excellent thermal insulator. so temperature changes take a relativly long time to travel through it. becuase of this, if you say pour boiling water into a room temp glass, the inside will expand before the outside even gets hot. the inside expanding against the smaller outside creates huge internal stresses. glass is extremely brittle and this stress easily will crack it.
borosillicate glass (pyrex just a name brand) has a very low coefficient of thermal expansion. that is, it expands very little for a given temperature difference. this lets it withstand much greater thermal conditions then normal glass. thats why pyrex glass is used for baking dishes, scientific test tubes etc and even smoking pipes.
mason jars work fine in a boiler for canning becuase the ENTIRE jar is heated up ant a CONSTANT rate and very SLOWLY. glass can handle any temperature you want just fine. but its thermal gradients within it that will quickly shatter it.
so having the bottom half full of hot ethanol and the top exposed to air is a BAD idea.