# Don't use glass to mix lye?



## kniquy (Jan 3, 2019)

Just reading through the thread on advice you would give your beginner soap maker.  I was surprised with the first one - - don't mix lye in glass.  I feel like i have seen many videos and they mix the lye in a glass container.  I know it needs to be heat resistant - so would my pyrex measuring cup be acceptable? or a glass beaker?  

The beakers I purchased have this statement: "This product is designed for heating by hot plate, flame, oven, microwave or heating mantles. In normal service it can be heated many times to 230°C."   

I would presume this would be safe to use for mixing lye, but please correct me if i am wrong. I'm not sure what high temp the lye can reach.


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## shunt2011 (Jan 3, 2019)

I would not use any glass to mix lye.  It can etch it and cause it to break/shatter.  There are many discussion on this forum explaining it and the reasons.   Not worth the risk.


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## IrishLass (Jan 3, 2019)

Here's a direct link to post I wrote not too long ago that lists the several reasons for not mixing lye in glass....not even in tempered glass:

*https://www.soapmakingforum.com/thr...x-your-lye-and-water.68945/page-3#post-690284

*
IrishLass


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## DeeAnna (Jan 3, 2019)

It's not the temperature -- heat treated glass is fine from that standpoint. The hazard comes from the highly concentrated alkali solutions we use for soap making. Alkali (KOH or NaOH) chemically damages the glass and makes it more prone to breakage. Irish Lass's article explains more.


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## kniquy (Jan 3, 2019)

IrishLass said:


> Here's a direct link to post I wrote not too long ago that lists the several reasons for not mixing lye in glass....not even in tempered glass:


  So what should i look for in a plastic (or whatever type) container which would be safe and appropriate to mix lye


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## IrishLass (Jan 3, 2019)

The best, most common/readily available safe plastics to use for mixing lye are PP #5 and HDPE #2 (look on bottom of container for recycle codes in triangle).  Steer clear of PETE (as me how I know ).


IrishLass


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## dibbles (Jan 3, 2019)

Stainless steel is also good. I use a stainless frothing pitcher, dedicated to mixing lye solution.


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## Zing (Jan 3, 2019)

Ditto to all of the above.  This newbie's big mistake was that while I did not use glass for lye, I thought nothing of inserting a glass thermometer into my lye solution and keeping it there to watch the temperature.  One day the thermometer fell apart in my hands.  I wasn't hurt but it could have been worse.


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## dxw (Jan 3, 2019)

Strong hot alkali (soapers' lye) attacks the Silicon - Oxygen bonds in glass, and literally dissolves the glass. Original pyrex was a borosilicate glass, more chemical and thermal stable than most, but it was still glass. Modern pyrex is not so resistant.

What happens is the lye slowly eats away at the glass, making it weaker in some areas. Then, one day, when you put something hot into that weakened  glass container the (entirely normal) heat expansion forces are spread out unevenly and the stresses exceed what the glass can cope with. This results in the glass breaking. That breaking process can be quite 'explosive' and, worst case, could result in hot lye being spread widely.

I have pyrex but am on the lookout for suitable stainless steel containers … and posting this reply prompts me to make another round of the 'op-shops' hereabouts.


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## lsg (Jan 4, 2019)

I don't use glass anymore, either.  I use a NORPRO funnel pitcher.


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