this post was submitted on 21 Jun 2026
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I don't know how to answer that. It doesn't say Pyrex but I assumed the type of glass is the same formulation and just not using the brand name?
All caps PYREX good borosilicate. Lowercase Pyrex crappy soda-lime.
Turns out it's not as simple as that, and there is no real certain way to tell. This video goes into some good detail:
https://www.youtube.com/watch?v=2DKasz4xFC0
Borosilicate and soda lime glass have a notably different index of refraction.
Submerged in mineral or vegetable oil, soda lime glass will be clearly visible, while borosilicate will disappear.
The video goes over that too. He tries both types of glass in mineral oil and there is little to no visual difference. Not saying that's always the case, but again it's not so simple.