When I was little, I accidentally shattered a glass cooking instrument due to applying far too drastic a temperature change to it. Since then, I've been a bit afraid of doing it again. Of late, I've been using a french press to make coffee; one that happens to be made of glass. Since I am now pouring almost boiling water into a room temperature glass object, I'm a bit worried it will shatter. Double so since if it does, I could have almost boiling water flowing from my desk to my lap.
After dozens of uses, there hasn't been a problem. And if there would've been one, I don't think they would have been allowed to sale it. But I'm still concerned about how cold it can still be used at. For example, if I leave it in my car on a cold night and bring it into the office, can it be used straight away?
So why doesn't it shatter and how cold can it be before I need to worry?
Demensions: roughly 20cm tall with a diameter of 10cm, if that is of any relevance.
Material: Glass, I assume a special kind that is better able to handle heat, but I don't kow the details.
Best Answer
As PMPJohn mentioned, it's probably made of Pyrex (a borosilicate glass). This material has about 1/3 the thermal expansion of conventional glass, so thermal stresses are much lower and it can easily accommodate the kinds of thermal shock you describe.
Interestingly, glass made today in the US under the Pyrex name is actually no longer borosilicate glass, but is instead tempered conventional glass. It appears to be less resistant to thermal shock than borosilicate glass. In Europe, a similar brand-name is Duran, which still is borosilicate.
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