> All of the glass examples in TFA are borosilicate all-caps PYREX, while most of what you can buy today in the store is lowercase pyrex (Europe is an exception where the all-caps variety can be found).

Using all-lower or all-upper case is not a good indication of the type of glass used.

A recent video (Sep 2025) from the I Want to Cook channel, "PYREX vs pyrex -- What's The Difference & Why It Matters", went into the history of this:

* https://www.youtube.com/watch?v=2DKasz4xFC0

Specifically, he found the following at the Corning Museum of Glass site:

> The short answer is that the change from Pyrex trademark upper to lower case signified a re-branding of the trademark Pyrex® in the late 1970s but is not a conclusive way to determine, historically, what type of glass formulation the product is made from.

* https://libanswers.cmog.org/faq/398431

So if someone goes to thrift stores looking for borosilicate via the 'old way' of spelling the name, there is no guarantee it will be borosilicate.

See 16m11 of the video for advice if you want borosilicate glass: in Europe, it is all borosilicate; in US, import it yourself, look for "Made in France", or use another manufacturer (e.g., Oxo names the glass they use).