# Testing for lye strength



## Katherine1121 (Jan 7, 2021)

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???


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## DeeAnna (Jan 7, 2021)

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 (Jan 8, 2021)

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!!!


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## DeeAnna (Jan 8, 2021)

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.


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## Katherine1121 (Jan 8, 2021)

Here's the link: 

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


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## cmzaha (Jan 8, 2021)

Shame on her, she is mixing her lye solution in a Pyrex measuring cup.


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## DeeAnna (Jan 8, 2021)

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.


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## Katherine1121 (Jan 12, 2021)

DeeAnna said:


> 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.





DeeAnna said:


> 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.


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## Katherine1121 (Jan 12, 2021)

cmzaha said:


> Shame on her, she is mixing her lye solution in a Pyrex measuring cup.


Maybe she's using vintage pyrex??? 
Back in the day, Pyrex measuring cups were made from borosilicate glass...


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## SoapDaddy70 (Jan 12, 2021)

cmzaha said:


> Shame on her, she is mixing her lye solution in a Pyrex measuring cup.


If you watch a lot of Brambleberry Soap Queen videos she uses glass all the time.


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## ilonaliss (Jan 12, 2021)

SoapDaddy70 said:


> If you watch a lot of Brambleberry Soap Queen videos she uses glass all the time.



She does! It always struck me as weird...


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## DeeAnna (Jan 12, 2021)

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 (Jan 18, 2021)

DeeAnna said:


> 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)...."
> 
> ...


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## ResolvableOwl (Feb 8, 2021)

DeeAnna said:


> every soap recipe calc I know of doesn't let the user specify the NaOH purity in the calc











						Lye Calculator & Recipe Creator for Soap Making | LyeCalc
					

Advanced and beginner soap making calculator for soapmakers. Create solid,         liquid and cream soaps. Save your recipes with pictures and add custom ingredients &         instructions to share online. Join the web's best soap making community.




					www.lyecalc.com


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## TheGecko (Feb 8, 2021)

SoapDaddy70 said:


> If you watch a lot of Brambleberry Soap Queen videos she uses glass all the time.



Which doesn't make it right.  I frequently respond to NOT use glass.


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