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Soap Making Forum > The Soap Making & Craft Forum > Beginners Soap Making Forum > Is Pyrex all right for one use?
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Old 07-19-2017, 08:07 PM   #71
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Originally Posted by Helenz View Post
Ive been using my two pyrex jugs for the last 2-3yrs without any problems. Admittedly the soaping process is faster now that I know what Im doing and I make sure I clean up well. The jugs dont show any deterioration so far. cheers Helenz
You are in New Zealand. Pyrex made by Corning sold in NZ and Australia is different from that made in the USA. If it is made by Corning in Australia it will be the safer than that made in the US. The capital lettering on the container is one indication but there is also smaller writing saying where it is made. Google Pyrex for more info. It was a "good" Pyrex container that exploded on me. I still don't trust it for hot liquids.

It would be good if you added your location to your name to avoid confusion.

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Old 07-22-2017, 07:41 PM   #72
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You need to be aware that "pyrex" means two different things -- it's a registered trademark for borosilicate glass by Corning, and in the old days, before the word became generic (and everything wasn't made in China) the "Pyrex" marking meant borosilicate glass. While it will eventually frost, it's OK to use a few times.

Sadly, someone got all bent out of shape about the miniscule amount of boron that CAN (note I said CAN) leach out of borosilicate glass, and it was banned from food use. That means "Pyrex" became a trade name for glass cookware, and it's quite dangerous. Lots of reports of exploding "Pyrex" pans, etc because tempered glass is NOT borosilicate glass, it's silica based glass and quite fragile in comparison. It will indeed shatter unexpectedly under thermal stress, and does not have to be etched by lye first, although that will make failure more likely rather than less.

So, bottom line, unless you KNOW your "Pyrex" container was made before about 1986, assume it's plain tempered glass and do NOT mix lye in it, it's subject to thermal stress cracking, a bad thing. Older Pyrex is probably quite safe -- I use it in the chemistry lab all the time for making strong lye solutions and have never had a beaker break, even a badly etched one. Lots of plain glass failures though.

Plastic or stainless is safer, and you really don't want hot lye running all over your countertop....


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