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Testing for lye strength

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Katherine1121

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Anybody watch HSCGs how-to YouTube Cream Soap video by JThompson? In it she talks about the need to test the strength of opened containers of NaOH & KOH since they can become weak over time - especially KOH. She doesn't explain how to test but says SAP would need to be adjusted. Anybody know how? I'm confused. It would be nice if you could watch the YouTube video to maybe understand why I'm confused. She talks about adjusting the recipe if the strengths are off (makes sense) but the math looks weird then talks about adjusting the SAP (doesn't make sense), I'm sure she knows what she's doing but also appears very nervous... The part about verifying the strength of previously opened bottles of hydroxides makes sense but I can't find/don't know the methodology used to do so.... anybody know???
 

DeeAnna

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I don't follow Jackie Thompson, so I'm taking you at your word about Jackie doing something to adjust the saponification values. Honestly, that doesn't make a lot of sense to me without studying what she's saying, but I think I can answer your essential question without knowing her methods.

Yes, you can test the alkali purity of NaOH or KOH. The most rigorous method for kitchen chemists would be the procedure in Kevin Dunn's book Scientific Soapmaking.

I have a simpler but less accurate method here: NaOH or KOH purity check | Soapy Stuff

As you scroll down this webpage, you'll also see an easy method for correcting a soap recipe for less than 100% NaOH purity. Since every soap recipe calc I know of doesn't let the user specify the NaOH purity in the calc, you have to do this adjustment if you want to compensate for NaOH purity.

You'd adjust for the KOH purity exactly the same way if you are using a calc that does not let you adjust the KOH purity directly.

Two calcs I know of let you enter the KOH purity directly, however. Use either Soapmaking Recipe Builder & Lye Calculator or Soapee Lye Calculator, type the KOH purity into the calc, and build your recipe from there. Pretty easy once you have the number for the purity.

Another thing you might want to look into is you can do a lot to prevent the loss of purity by proper storage. The article on my website also gets into how to do this -- keep scrolling toward the end.
 
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Katherine1121

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Thank you for your reply... Adjusting the SAP didn't make sense to me either... I've taken a fair number of chemistry classes in my lifetime but the last one was more than 40 years ago (yes, I'm old)... there were a couple of other statements during the video that didn't make sense... although I have her book on liquid soapmaking, I don't follow her either... she made the video for HSCG and I honestly think she appeared a bit nervous... rather than waiting for a reply to a YouTube comment, I thought I'd get a more complete & expeditious answer on this forum - and I was right!!! I'll be sure to spend a bit of time on your website... I'm driven by curiosity and anal enough to take the time to check the purity of my hydroxides just for the fun of it!!! the math that follows alterations in purity seems straightforward enough... thank you again, DeeAnna... I really appreciate the thoroughness of your response... it brought contentment to my brain!!!(🙃)... BTW, I very much like the geeky stuff!!!
 

DeeAnna

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You're welcome -- glad I could help.

If you try the "easy" method of testing lye purity that I give on my website, I'd appreciate a critique of how easy it is to do and whether you get answers good enough for your purposes.

Back to the video presentation -- Adjusting the sap values to compensate for the alkali purity seems like a cumbersome and indirect way to make a correction. If you'd provide a link to that video, I'd give it a watch one of these days -- I'm curious about this.
 

Katherine1121

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Here's the link:

The title of the YouTube video is
HSCG How-To: Cream Soap with Jackie Thompson - Advanced Technique
 

Katherine1121

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I watched the video through the adjustment to the sap value to account for the lye purity. Maybe this works for her, but I am really not following her reasoning.
I had issues with it as well which is why I brought up the question here...
I read the post on your website, and watched your YouTube video... both are great... I really liked the pdf you created on your website, too - it's quite thorough and easy to follow... from the YouTube video, the only "critique" I'd have is that rather than using any jar or even a canning jar to mix the solution, I'd want to use borosilicate glass... most canning jars are non-tempered soda-lime glass and, although more impact resistant than borosilicate glass, are more susceptible to thermal shock. Back in the day (prior to 1998?), Pyrex measuring cups were made from borosilicate glass... nowadays, Pyrex measuring cups are made from tempered soda lime glass. Borosilicate measuring cups, and beakers with or without handles can easily be acquired on Amazon. Also, rather than picking up the solution to swirl over the sink, I would use either a long-handled stainless steel, or heat-resistant glass stirring rod or spoon to stir the mixturewhere it sits. LOL, knowing me, and the fact that I'm unable to do the swirling-in-the-wine-glass thingy to create the little whirlpool without splashing, I'd likely cause the test solution to splash out of the container and onto my hands, thus the need for me to use a stirring instrument.
Again, it's probably my chemistry background that drives me towards the use of borosilicate glass... I like its thermal resistant, nonporous characteristics.
 

DeeAnna

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Regarding soap making and the use of borosilicate glass versus any other kind of glass --

Many people here, including me, don't recommend the use of any kind of glass, including lab quality borosilicate, for mixing or storing concentrated lye solutions or for making soap. Borosilicate has definitely been shown to micro-etch from exposure to concentrated alkalis and this etching causes it to become more prone to unexpected breakage.

Furthermore glass, any type of glass, even the best kind of glass, will invariably break if you drop it. If you drop a glass container of concentrated lye or lye-heavy soap batter on the floor, you're going to be handling shards of broken glass along with mopping up hazardous lye or soap batter. A cut that gets contaminated with concentrated lye will result in a painful, slow healing injury. A chem lab has the proper tools to handle this kind of accident. The average soap maker working in the average kitchen does not.

Even if you love borosilicate and think it walks on water, it's still far better to use an HDPE (high density polyethylene) or PP (polypropylene) plastic container (recycle code #2 or #5). Plastic containers eliminate the broken glass problem and the right plastic material offers excellent resistance to concentrated alkalis and heat.

***

"...the only "critique" I'd have is that rather than using any jar or even a canning jar to mix the solution, I'd want to use borosilicate glass..."

I understand your concern. I am aware that using canning jars is not something a real chemist would think is appropriate. And I want to stress again that using any kind of glass in soap making is NOT my normal habit. But in this one situation, yes, I am making a calculated exception to this general rule.

The only reason why I'm making this exception is some kind of clear container must be used to see the color shift in this test. If I could have used plastic, I would have, but lye-safe plastics are translucent not clear and transparent plastics such as PET (polyethylene terephthalate) are not lye safe. Hence the use of clear canning jars -- they are the most reasonable option for the average person.

This method has to be practical for the average person to do, and that goal requires a few compromises. One compromise, obviously, is the canning jars versus lab-grade borosilicate flasks. Another is doing a "titration" with dry citric acid powder rather than a standardized acid solution. I understand why these compromises would curl the hair of any competent, self-respecting chemist. But these compromises make this test a reasonable one for the average person to do.

***

"...rather than picking up the solution to swirl over the sink, I would use either a long-handled stainless steel, or heat-resistant glass stirring rod or spoon to stir the mixture where it sits ..."

In a titration, swirling the liquid solution is the accepted protocol. That's why Erlenmeyer flasks are often used for titrations -- so you can swirl more easily.

In the lye purity test video, there is only about 100 mL of liquid in a pint (500 mL) jar. There is a lot of headroom in the jar to corral this amount of liquid. And for added insurance, the video also shows me wearing gloves and swirling the jar in the sink. The risk involved in swirling the liquid in this situation, IMO, is pretty low.

Using a stirring implement isn't risk free. It introduces errors that can throw off the accuracy of a titration. A stirring implement will also raise the center of gravity of the container and increase the chance of a tip-over and spill.

I would also move the container off the scale even if I did use a stirring implement. Always move the container off the scale platform before doing any manipulations like stirring. If you don't, that's a great way to ruin a good scale.

edited for clarity and to fix typos
 
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Katherine1121

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Regarding soap making and the use of borosilicate glass versus any other kind of glass --

"Even if you love borosilicate and think it walks on water, it's still far better to use an HDPE (high density polyethylene) or PP (polypropylene) plastic container (recycle code #2 or #5)...."

"Many people here, including me, don't recommend the use of any kind of glass, including lab quality borosilicate, for mixing or storing concentrated lye solutions or for making soap...."

***
LOL, 😂 I don't think borosillicate walks on water! It's as I said, my last chemistry class was more than 40 yrs ago, back when bakeware and measuring cups were made from borosilicate glass - thus my lean towards borosilicate. Still, borosillicate beakers and flasks are what I use for making my very, very small batches of skincare products - NEVER for making soap, and NEVER for mixing or storing strong solutions of lye. Personally, I use a stainless steel pitcher for mixing my lye and, because I'm trying to minimize my plastics footprint, a stainless steel pot to make CP soaps - for anything HP, I use a crockpot designated for soap...

"I am aware that using canning jars is not something a real chemist would think is appropriate. And I want to stress again that using any kind of glass in soap making is NOT my normal habit. But in this one situation, yes, I am making a calculated exception to this general rule.

"The only reason why I'm making this exception is some kind of clear container must be used to see the color shift in this test
. "

"If I could have used plastic, I would have, but lye-safe plastics are translucent not clear and transparent plastics such as PET (polyethylene terephthalate) are not lye safe. Hence the use of clear canning jars -- they are the most reasonable option for the average person."

"This method has to be practical for the average person to do, and that goal requires a few compromises. One compromise, obviously, is the canning jars versus lab-grade borosilicate flasks. Another is doing a "titration" with dry citric acid powder rather than a standardized acid solution. I understand why these compromises would curl the hair of any competent, self-respecting chemist. But these compromises make this test a reasonable one for the average person to do."


I hope I didn't leave you or anyone else with the impression that I'm a trained chemist because I'm not... If that's the case, albeit unintentional, please accept my apology.

I'm a retired pharmacist - taking lots of chemistry classes was simply a requirement for my degree. I actually spent most of my career behind a desk, focusing on the clinical and administrative aspects within my practice setting.

I agree with you, DeeAnne.. a clear glass container is absolutely necessary in order to detect the shift in color... I don't believe it can be done any other way... I should've said and it would've been more thoughtful for me to say that I'd use borosilicate, primarily because I have it... even my measuring cups are from 45 years ago, and likely borosilicate... again, I'm sorry for sounding "absolute."

On the "bright" side of things... the topic of borosilicate vs tempered soda-lime glass caused me to look more deeply into the subject... Just this morning, I found this on the Anchor Hocking website: Bakeware Facts
Could be the reasoning behind/justification for Anne Marie's use of glass in her soapmaking demonstrations????

Still, there exists relatively recent articles such as this August 13, 2020 article from from the NYTimes that seem to lean towards one glass type or the other, depending upon its intended use:
Or this undated article containing links to other articles about glass:

It's as I said, I kinds like the nerdy stuff🙃...
***

"...rather than picking up the solution to swirl over the sink, I would use either a long-handled stainless steel, or heat-resistant glass stirring rod or spoon to stir the mixture where it sits ..."
Again, the above response is just this is just a reflection of me... No matter how many times my husband has tried teaching me, I simply can't swirl anything without splashing. Once, in college, an acid I was dispensing splashed onto my clothing and almost instantaneously ate through the fabric. That experience taught me to treat chemicals with the respect they demand, a practice I'm certain every soapmaker implements... Not only that, since developing fibromyalgia, I have a tendency to drop things - I've broken so many wine glasses that I'm no longer "allowed" to have wine in the "good" glasses... 🥴 It's as if the pain in my hands prevents me from gripping onto things as much as is necessary to stop things from tumbling out of my hands! I imagine this might also be the case for people with arthritic hands, depending upon the severity. I just assumed a suggestion such as this might be helpful to others...

"Using a stirring implement isn't risk free. It introduces errors that can throw off the accuracy of a titration. A stirring implement will also raise the center of gravity of the container and increase the chance of a tip-over and spill."

I'm not sure how a stirring instrument might throw off the accuracy of the titration procedure you've provided... I would think that by recording the weight of your container PLUS your stirring instrument prior to placing anything into the container, AND keeping the stirring implement in the container during the entire process, one would still be able to determine the amount of NaOH, or KOH necessary to illicit a color change in your citric acid solution and perform the necessary calculations. Admittedly, my fibro brain doesn't work as well as it did pre-fibro... I'm sure you'll be able to clarify how this the stirring instrument could throw off the accuracy of the titration.

I think the risk of a tip-over could be mitigated by selecting a stirring instrument that wouldn't offset the center of gravity to that extreme. The stainless steel mixing spatula/spoon set I have varies in size from as short as 10.5 cm (4.13 inches) to as long as 22 cm (8.66 inches), with another six lengths between the two. I think this relatively inexpensive set is similar:

"I would also move the container off the scale even if I did use a stirring implement. Always move the container off the scale platform before doing any manipulations like stirring. If you don't, that's a great way to ruin a good scale."

Great reminder!!! DeeAnne, your thoroughness of thought is UBER IMPRESSIVE!!! I'm certain that all of the issues you've brought forth would have become self-evident once I actually performed the test... Once again, I thank you so very much for all your help and the food for thought you've provided... it's how I learn... 🤗
 

ResolvableOwl

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