what makes some glass containers super heat proof and others crack under heat?
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Most materials expand when they heat up. Glass, in particular, is a really good insulator (doesn’t conduct heat well) so when you heat it up the surface that’s exposed to the heat it can get a lot hotter than the inside that hasn’t warmed up yet. That means different parts of the glass expand different amounts, which causes stress, which leads to cracking. Something similar happens if you take hot glass and cool it down quickly, like putting cold water in a hot glass dish.
However, it’s possible to design materials that don’t expand much with heat, sometimes called “low-expansion glass”. This involves mixing a bunch of other materials into the glass, often a lot of boron, when it’s called “borosilicate glass”. Most people know that by it’s trade name, Pyrex. Since this doesn’t expand as much with heat, the stress isn’t as high and it’s much less likely to crack.
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