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Comment by bmelton | Hacker News Reader

I went through this recently as I was buying housewares for my soon-to-be-moving-out daughter, and I was shocked to learn there's a pretty easy hack to knowing which Pyrex is which (at least for modern versions)

-- The good borosilicate glass is branded with uppercase "pyrex" -- The potentially bad soda glass is branded with lowercase "pyrex"

There are other clues too, like that the borosilicate ones aren't typically sold in the US, ergo typically aren't marked with imperial units, but if you're on the prowl for one or the other, upper/lower case is the surest giveaway

(unless there are some counterfeits I have not knowingly encountered)

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For what it's worth, the article says the exact opposite

  Protip: Look for all-caps PYREX graphics which can either indicate that is vintage or that it’s from Europe, where a company called Arc International owns the Pyrex brand and still makes its cookware out of borosilicate.

I was just editing (thought it funny after I typed it and went downstairs to look)

Thanks for the correction!

Borosilicate glass is also very noticeably lighter than normal soda-lime glass.

After you have handled both kinds of glass it is difficult to confuse them, especially in bigger vessels.

Besides the fact that borosilicate glass has a lower density, the vessels made of borosilicate glass are made typically with thinner walls than those made of normal glass, which makes even greater the weight difference.

Yeah if you're holding them in your hands they're very clearly different in weight and also color

I just wasn't savvy to this knowledge when I was shopping for them on the internet until I dove deeper

You have it flipped. The "good" versions are in all caps, the newer models are lowercase. I have some old, borosilicate pyrex and the name is capitalized. If you look up a new pyrex measuring cup, you'll note that the name is lowercase.

Yep! Edited. Thanks

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