Glass and lye; truth or myth?

[mrssoapandclay]

Thanks, I just saw your other comment and do appreciate the info.

The person who said the discussion was banned here is flat-out wrong - it is not banned.

Like every other forum, there are always some members who misstate things, whether innocently or bc they love stirring up stuff and getting folks riled up. My policy is to ignore them bc nothing productive comes from engaging.

They didn’t state that; I misunderstood the message and they clarified. I appreciate the advice on how to handle bad actors on this forum, but I’m really only here because I stumbled upon this thread during research for a video and thought it was funny. My community doesn’t tolerate misinformation or any activities that would make someone feel like they have to “ignore” another user for fear of attack. I doubt I’ll stay long.

 

[Kiti Williams]

They didn’t state that; I misunderstood the message and they clarified. I appreciate the advice on how to handle bad actors on this forum, but I’m really only here because I stumbled upon this thread during research for a video and thought it was funny. My community doesn’t tolerate misinformation or any activities that would make someone feel like they have to “ignore” another user for fear of attack. I doubt I’ll stay long.

After reading all of your posts on this thread, I have come to the conclusion that I really like you. Please consider staying.....

 

[mrssoapandclay]

Nope, the discussion is not banned. The official SMF position is that glass is not recommended, but discussion of the science and the practical considerations is allowed.

I personally haven’t seen anything scientific that contradicts the manufacturer’s website about lye solutions etching borosilicate glass. But I and many others here are always open to hearing and learning more. So I hope you are able/willing to contribute to the discussion.

EDIT: just saw your prior comment with the long-form explanation. Thank you for being as wordy as I am! I actually use a 40% lye concentration in almost all my soaps, but it is room temp bc I masterbatch at 50%. And my understanding is that temperature does make a difference here. Any chance you would share a link or two to the articles/experiments you mentioned? Thanks!

Yes, keeping a lye solution at 100 degrees consistently in plastic or glass for incredibly long periods of time will lead to degradation. So temperature is a factor, like it is with almost anything else you own or use on a daily basis. There are white pages aplenty on the subject, which I link in a bunch of videos but I’ll see if I can find time to pull some for you - after I finish making my coffee at 200 degrees in a tempered glass carafe.

 

[paradisi]

No matter how many times a few individuals claim that lye in glass is perfectly safe or that they never had a problem, those are not proof of safety, they are just claims.

And being told that their method can be harmful doesn't make a person a victim.

On a site that welcomes beginners, teaching actual safety is important.

Many people do reckless things, and get away with it, but that's no reason to encourage or brag about it.

They won't be there to take you to the hospital or buy you a new pitcher.

And sadly yes some like to dredge up old hot topics to get attention.

 

[mrssoapandclay]

No matter how many times a few individuals claim that lye in glass is perfectly safe or that they never had a problem, those are not proof of safety, they are just claims.

Loads of scientifically backed, quantifiable evidence exists that runs contrary to your anecdotal claim that has to use shock effect language to make anyone pay attention. The hospital?!? That sounds scary. Better go cover myself in bubble wrap and throw out everything in my life that has the same potential for harm. Goodbye to my curling iron, or my instapot, all of my baking dishes, and certainly all trees on my property - all things that have a higher likelihood of injuring you. Teaching safety IS important, and when used properly glass is safe.

I’ve spent my entire life using glass for all manner of things in all manner of situations, from chemistry labs and baking to shelves and soapmaking. My husband is a subject matter expert in the field and is responsible for the structural integrity of the glass in high rise and high security buildings, which includes considerations for physical and chemical attacks. If glass were as scary as soapmakers seem to believe, it wouldn’t be used in any of these environments. But go off about how glass safety is an unfounded claim and just an opinion.

Nope, the discussion is not banned. The official SMF position is that glass is not recommended, but discussion of the science and the practical considerations is allowed.

I personally haven’t seen anything scientific that contradicts the manufacturer’s website about lye solutions etching borosilicate glass. But I and many others here are always open to hearing and learning more. So I hope you are able/willing to contribute to the discussion.

EDIT: just saw your prior comment with the long-form explanation. Thank you for being as wordy as I am! I actually use a 40% lye concentration in almost all my soaps, but it is room temp bc I masterbatch at 50%. And my understanding is that temperature does make a difference here. Any chance you would share a link or two to the articles/experiments you mentioned? Thanks!

EDIT: just saw your prior comment with the long-form explanation. Thank you for being as wordy as I am! I actually use a 40% lye concentration in almost all my soaps, but it is room temp bc I masterbatch at 50%. And my understanding is that temperature does make a difference here. Any chance you would share a link or two to the articles/experiments you mentioned? Thanks!

To get you started. For funsies, start pH testing your various lye solutions before making soap with them and see the differences in dilutions!

https://www.dedietrich.com/en/solutions-and-products/enamel-borosilicate-glass/borosilicate-glass
https://www.corzan.com/blog/cpvc-chemical-resistance-to-caustic-soda-sodium-hydroxide
https://www.researchgate.net/post/C..._make_channels_on_glass_with_sodium_hydroxide
https://www.chemicalforums.com/index.php?topic=29661.0

 

[ScentimentallyYours]

Hmm . . . I work in fused glass and use an acid etch on a regular basis. It would be easy enough to drop a piece of glass into 50:50 lye solution and see how long it takes to produce visible etching. Not terribly scientific from a standpoint of publishing, but something that would satisfy my curiosity. I can drop a piece of dichroic glass, too, to see if it dissolves off the surface.

Of course, now that I think about it, since I use an acid to etch my glass, maybe I should be more careful of acidic contents like vinegar in glass? (Just kidding)

 

[mrssoapandclay]

Hmm . . . I work in fused glass and use an acid etch on a regular basis. It would be easy enough to drop a piece of glass into 50:50 lye solution and see how long it takes to produce visible etching. Not terribly scientific from a standpoint of publishing, but something that would satisfy my curiosity. I can drop a piece of dichroic glass, too, to see if it dissolves off the surface.

Of course, now that I think about it, since I use an acid to etch my glass, maybe I should be more careful of acidic contents like vinegar in glass? (Just kidding)

This may be the best comment I’ve ever read. +1 for logical thought and an experimental spirit.

 

[ScentimentallyYours]

This may be the best comment I’ve ever read. +1 for logical thought and an experimental spirit.

Experimental spirit . . . Yes, that’s me! Check out
Crown Soap, Ben Franklin’s Family Recipe
And
Post in thread 'Brine soap who created this soap'
Brine soap who created this soap

And then there’s my experiment with salting out scraps here
https://www.soapmakingforum.com/threads/salting-out-scraps.84847/post-904592
Those of us who stick around here tend to be curious and embrace science. I have found members of SMF to be incredibly supportive and generous with good information. And a number of us post more information than may be needed or wanted, but people are kind enough to just skip over it and not say anything because they are so polite.

 

[Mobjack Bay]

I personally don‘t use glass in soap making due to the potential for breakage, but now my interest is piqued enough that I’m going to have to ask my chemist friends what kinds of containers they use to make and store lye or other strong alkali solutions. In the interim, I poked around a little and found the following.

According to Sigma-Aldrich, a major supplier of reagent grade NaOH:

“Sodium hydroxide stock solutions should be stored in plastic containers. Glass containers should be completely avoided in the preparation and storage of sodium hydroxide solutions.”

As for experimenting, here are some data from a manufacturer of high end/technical glass products. The amount of borosilicate glass removed/etched by alkali solution per unit of time increases with pH (concentration) and the rate increases rapidly at pH > 12, as shown in a graph posted here.

More on that, here, along with descriptions of the many different types of borosilicate glass made by the company.

Interestingly, a conservator at The Corning Museum of Glass suggests that we use a 10% lye solution to remove burned on residue from Pyrex glassware, as described in this article. On the other hand, he warns against running Pyrex through the dishwasher:

“First, never, ever put any Pyrex through a dishwasher. This is the fastest and most damaging thing that you can do. It will slowly etch the Pyrex, and probably will not even do a decent job cleaning it. I generally recommend that you never put any glass through a dishwasher.

Second, never use any scrubbing sponge, even if it says “safe for glass,” or “non-scratch.” This includes wire wool cleaning pads.

Also avoid using sharp implements to clean off caked-on or burnt food. Glass can easily be scratched.”

 

[ScentimentallyYours]

According to Sigma-Aldrich, a major supplier of reagent grade NaOH:

“Sodium hydroxide stock solutions should be stored in plastic containers. Glass containers should be completely avoided in the preparation and storage of sodium hydroxide solutions.”

@Mobjack Bay, do you think they said this because if you drop a sealed glass container (versus a sealed plastic container), the glass may break? I’m just wondering if it’s not actually a case of the glass being etched to the point of destruction.

It makes sense to me that people combine a fear of glass with the fear of sodium hydroxide. When I teach children or intellectually disabled adults how to cut glass, the first thing I teach them (with humor) is how to cut their fingers on glass. No, they aren’t supposed to do it, but they learn and remember what not to do. It allows them to be more comfortable handling glass safely.

The comment about dishwashers etching glass makes sense to me because back in the day when I had a dishwasher, my glasses showed etching damage. Now I wash all of my glasses by hand. (Not really by choice.) I sure do miss having a dishwasher.

P.S. We cut glass by scratching it (called scoring) and putting pressure on the scratch. Maybe the cautions about not scratching glass containers are more relevant than they first appear?

 

[mrssoapandclay]

I love this! I highly recommend talking to chemists about all manner of things, but I am biased. In-line, because it’s a long one.

According to Sigma-Aldrich, a major supplier of reagent grade NaOH:

“Sodium hydroxide stock solutions should be stored in plastic containers. Glass containers should be completely avoided in the preparation and storage of sodium hydroxide solutions.”

This is an interesting example of companies and their CYA statements because of the litigious world we live in. Kinda like McDonald’s coffee. 1) Sigma Aldrich also sells glass rated for alkali solutions, on the same website. So it’s safe or it isn’t? 2) the SDS pages, which are wildly more important than a product description as the SDS are regulated by OSHA and follow a strict set of guidelines, have, in addition to all material conflicts and dangers, a section specifically for storage of any chemical including incompatibilities. Glass is not included anywhere in these SDS pages, and it would be if it presented a danger. For funsies I also pulled a lye solution SDS because things get messier when water is added to lye. Glass is also not mentioned.
OSHA’s regs are here
SDS for above lye here
SDS for lye solution here

Net/net: if glass use posed a risk, it would be stated. Because OSHA says it has to be and they’ve shuttered businesses for less.

As for experimenting, here are some data from a manufacturer of high end/technical glass products. The amount of borosilicate glass removed/etched by alkali solution per unit of time increases with pH (concentration) and the rate increases rapidly at pH > 12, as shown in a graph posted here.

I love this graph so hard, and I don’t know if you’re meaning to prove my point with it or not. This series says exactly what I posted earlier in the thread but using different units of measure. The conclusion is the same; the corrosion is inconsequential and nearly imperceptible under highly elevated temperature conditions. 212 degrees over three hours yields a micrometer of loss? That’s 1/1000th of a millimeter. Read: lye is not efficient at etching glass. Conclusion: don’t keep your lye in a boiling state for any period of time.

To the rest, yes a lye solution is good for removing stains (mineral deposits et al) on glass. And yeah don’t scratch your glass, because then it looks scratched. But surface abrasions also don’t critically impact the strength of the glass. And it doesn’t surprise me about the Pyrex guy saying not to wash glass in the dishwasher - water is a beast of a corrosive for loads of things, and items in the dishwasher undergo physical attack because they’re being blasted with water.

 

[TheGecko]

My community doesn’t tolerate misinformation or any activities that would make someone feel like they have to “ignore” another user for fear of attack.

"Fear of attack"...that is too subjective. Speaking in general...there are folks who construe any disagreement with their way of thinking as an 'attack'. There are folks who don't like being told that what they are doing is wrong and see it as an 'attack'. There are folks who if you don't speak to them like they are made of spun sugar, see it as an 'attack'. I have a few folks here that I have on 'ignore' and I'm sure there are folks here that have me on 'ignore'...and it's okay because not everyone HAS to like one another.

"Misinformation" is also subjective. Example...that handcrafted soap is 'safe' to use after it has fully saponified. That is true...the Sodium Hydroxide is fully used up and turned into soap and thus it is 'safe'. But is it good soap? No...freshly made soap is harsh and soft. It needs to cure four to six weeks for not only water evaporation to make it a longer lasting soap and for the crystalline structure to form to make it a gentle bar of soap.

Another is this very conversation...is it safe to make soap in a glass bowl and/or make your Lye Solution in a glass jug? In the short-term...one can yes. In the long-term...one can say no. I'm in my early 60s and started cooking/baking when I got my first set of child's cook/bakeware when I was in 4th grade...it was really cook/bakeware that could be used on the stove or oven. I've seen what metal implements...spoons, forks, butter knives, pancake turners, whisks and beaters can do to all forms of glass and ceramics, and even stainless steel...it scratches the surface, it can create chips (glass). And once that starts happening, it weakens it and overtime, the glass will break...when it gets too hot, when it gets cold, when you tap a teaspoon against it. Now add a caustic substance to it. Doesn't matter that it's only 33% or 35% or 40% Sodium Hydroxide...it gets into the scratches, the chips and weakens it further. If you're only making small batches of soap once a week, you'll probably never have to worry about it, but if you're making 25lbs or more soap every day...you might want to rethink using glass. I've had a measuring cup of boiling water shatter on me...I jumped fast enough when I heard the glass crack that I didn't get burned and I just walked away until the water cooled enough that I could safely clean it up. Now imagine had that I had just poured Sodium Hydroxide into my room temp water which quickly accelerates to about 210F-220F? I've got a scar on the top on my right foot from a single grain of Sodium Hydroxide that I was too lazy to clean off because I was in the midst of a soap session. I also have a few browns spots on my kitchen floor from not cleaning up as well as I should have after my husband knocked over my weighed out Sodium Hydroxide. I can't even being to imagine how bad it would be to have a chemical burn on top of a thermal burn, when the simplest solution is to not use glass.

 

[Vicki C]

I don’t use glass because I’m a clutz and I would eventually drop/break/nick the container.

 

[Misschief]

I don’t use glass because I’m a clutz and I would eventually drop/break/nick the container.

I don't use glass because why take the chance? I use stainless steel.

 

[2lilboots]

I use my glass stuff for baking and plastic/stainless for soaping. That way I don't mix them up.

 

[ScentimentallyYours]

I bought polypropylene pitchers for all my soap mixing and bottles for master batch storage. I like the lightweight pitchers/bottles with handles. They have a stable, flat, bottom, which makes them safer for me to use. I don’t use my soap utensils or containers with anything used for food, especially if they are made with silicone or plastic because they pick up the soap flavor.

 

[Shelley D]

I don’t use glass because I’m a clutz and I would eventually drop/break/nick the container.

I'm in that boat right there! That is exactly why I didn't buy any glass bowls! Stainless for melting (double boiler styler) and plastic for everything else! Because even with rubber gloves on I will drop a glass bowl ~ just saying! And after almost 50 years of hand washing dishes, I know what I know, ya know?

 

[TheGecko]

I don't use glass because why take the chance? I use stainless steel.

Having had glass break from cooking/baking I agree. I was using plastic for my Lye Solution and mixing in the sink, but recently switched over to a stainless steel pitcher for it. I'll still mix in the sink...one because that is where the window is and two, I can easily add cold water to the sink to cool it down faster.

I bought polypropylene pitchers for all my soap mixing and bottles for master batch storage. I like the lightweight pitchers/bottles with handles. They have a stable, flat, bottom, which makes them safer for me to use. I don’t use my soap utensils or containers with anything used for food, especially if they are made with silicone or plastic because they pick up the soap flavor.

I don't mix and match my soaping/cooking equipment either, but it's less about cross-contamination and more about convenience of not having to worry that something I need is in use or sitting in the dishwasher.

I'm in that boat right there! That is exactly why I didn't buy any glass bowls! Stainless for melting (double boiler styler) and plastic for everything else! Because even with rubber gloves on I will drop a glass bowl ~ just saying! And after almost 50 years of hand washing dishes, I know what I know, ya know?

When it comes melting oils and waxes, I prefer stainless steel and the stove as opposed to plastic and the microwave. For one, stainless steel cleans easier than plastic. Two, hard oils, butters and waxes melt faster on the stove. And I admit that I don't wear gloves...it's hard to tell when you get oils on them and the next thing you know, you have oils over everything. I keep a sink filled with hot soapy water and several microfiber towels (wet and dry) handy as I tend to clean as I go since I don't want a crap load of dirty dishes at the end of the day. The downside of so much hand-washing is having to use a few applications of hand lotion...palm oil is so drying.

 

[AliOop]

I don’t really understand why folks use a double-boiler to melt their oils. All that extra time, the water, the extra bowl… for what? You can easily achieve a low-temp melt in a stainless pot right on the the burner, turned down as low as you’d like.

To me, using a double-boiler to melt soaping oils is one of those soapy myths that is perpetuated despite providing no real benefit.

 

[Shelley D]

Having had glass break from cooking/baking I agree. I was using plastic for my Lye Solution and mixing in the sink, but recently switched over to a stainless steel pitcher for it. I'll still mix in the sink...one because that is where the window is and two, I can easily add cold water to the sink to cool it down faster.


I don't mix and match my soaping/cooking equipment either, but it's less about cross-contamination and more about convenience of not having to worry that something I need is in use or sitting in the dishwasher.

When it comes melting oils and waxes, I prefer stainless steel and the stove as opposed to plastic and the microwave. For one, stainless steel cleans easier than plastic. Two, hard oils, butters and waxes melt faster on the stove. And I admit that I don't wear gloves...it's hard to tell when you get oils on them and the next thing you know, you have oils over everything. I keep a sink filled with hot soapy water and several microfiber towels (wet and dry) handy as I tend to clean as I go since I don't want a crap load of dirty dishes at the end of the day. The downside of so much hand-washing is having to use a few applications of hand lotion...palm oil is so drying.

Ssshhh ~ I don't wear gloves either, but I didn't want to say put loud My back is literally to the sink when I work, plus I keep the vinegar handy just in case