Pyrex and Sodium Hydroxide

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Mar 22, 2015
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Mountains of West Virginia
Good Morning Everyone :mrgreen:

Last week, while looking for something else, I ran across a post about not using Pyrex when making your lye water, due to breakage. For the life of me, I can seem to find that post again.

But it has been a nagging worry now in the back of my mind, cuz guessed it. That's what I do. I don't recall reading about the "alternative" ??? Can someone help to clarify this for me.

Thank you for your time
It is not recommended to use Pyrex. It can fracture and explode or shatter due to etching of the glass. I use #5 plastic pitchers or stainless pitchers for my lye. I also always mix it in the sink.
There was a cautionary post on Facebook the other day where someone's Pyrex lye container had shattered all over her stove top and gone everywhere. It isn't a myth, it really can happen. You are better off with a plastic measuring jug. You need to ensure that it is the correct type of plastic though and off the top of my head I can't remember what numbers on the bottom are suitable. Hopefully someone else can help.
2, 4 and 5.

Pyrex used to be borosilicate glass which is also used in laboratories and relatively resistant to chemicals. But they're now using cheaper soda-lime glass which is not as chemically resistant and also shatters more easily due to temperature changes.
I buy stainless steel bowls in the section of walmart with spatulas, wisks etc. I like them for direct heating of oils on the stove, lowest of low setting. Worked for my almost 1 1/2 yrs of soapy adventures.
I even use my old lard tubs (5 in the little triangle). They work perfectly fine, and are completely safe. I gave a couple to co-workers who are starting their soapy adventures. They saw me use them, and it saved them from figuring out what to buy.
I mix my lye solutions as I need them. I only use plastic to mix my lye and liquid. I also set the container in the sink when mixing and leave sit it there until I am ready to mix the lye with oils and fats.
And even if the Pyrex doesn't explode, it can etch over time and leave micro slivers of glass in your soap, so it's just plain safer not to use it at all. I love using an old stainless steel sauce pan, because if I do need to cool the lye mixture in a hurry, it's super easy to just sit the pan in a bowl of ice water. Plus, it's easy to gauge the temp of the lye solution by touching the pan with the palm of your hand.
I get my lye from Essential Depot so I use the empty bottles to mix my lye water. I make mine as I go so can't speak to keeping a masterbatch in there, but since it's made to hold the lye itself, I would think it would not break down holding lye water.

I am one of the people who has had pyrex shatter. Thankfully, it shattered while in the dishwasher instead of all over my kitchen. Lesson learned.
You just have to be careful pouring the lye into the opening as it's narrow relatively speaking. You could use a funnel, but I just pour the lye in a thin stream and my surface is covered in plastic, so it all works out fine. I like that I can cap it as well if it's going to sit for a bit and then it doesn't get all crusty on the top.
I find a funnel difficult with lye, it seems to get stuck. I use a plastic disposable cup that bends which directs it into the neck of a bottle well. The containers they sell lye in are a special plastic and I like that some have "poison" molded into the side.

I like the plastic #5 jugs for mixing because I can see if it's all mixed.
WoW, thanks every body !

Well....can't say as I've ever heard of #5 plastic, but just did a google search. Hmmmmm. Interesting ! I have noticed the markers on plastic before but had no idea of what it actually meant.

I do have some large plastic bowls that would be perfect to mix my lye and water. I appreciate this tip, because my pyrex has been packed and moved numerous times over the last 5 years. So I can see now, where the tiniest crack could cause a shatter.

Thank you