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ConnorGoFuckYourself t1_j7yl6v4 wrote

Reply to comment by dkb52 in Got this old Tupperware brand set for $20 by CosmonautJizzRocket

Out of curiosity, do you think that old Pyrex is leaded glass?

As I'm pretty sure the old stuff is borosillica glass, the same stuff that laboratory glass is made from, which is why it was so heat resistant and doesn't leech anything out (chemists don't want lead to ruin their reaction and the glass needs to withstand sudden temperature changes).

Newer American Pyrex is much more brittle due to it using a cheaper glass (quartz or sodalime, if I recall correctly), though apparently European Pyrex is still borosillica.

Another fun one that you may remember; fiestaware, the really brightly coloured ceramic dinner sets that were popular in the 50s/60s, the red, yellow and orange (I think) contained uranium oxide as part of all of the brightly coloured glaze, an acidic meal such as spaghetti would leach significant uranium out. It will also make a geiger counter sing like a canary.

Whereas uranium glass (bright green and glows under UV) doesn't carry anywhere near the same risk of leeching.

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musclegeek t1_j7zpkar wrote

Just an FYI: Borosilicate glass is and has always been very easy to break from physical impact. The og Pyrex was no different. Pyrex changed it to Sodalime glass because modern everyday usage of glass cookware saw much more breakage from slight drops or impacts.

Yes, sodalime is much more sensitive to temperature gradients but we just don’t make many frozen casseroles anymore or really have a need to take a dish from a freezer to an over like they used to.

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dkb52 t1_j80y3r5 wrote

Yes. I guess my family dodged the bullet.

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