Help me understand lye concentration & water discount

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mzimm

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I'm new to soaping, having only about 20 batches of cp soap under my belt, as well as a few batches of liquid soap. Most have been fairly successful, if you count unplanned but otherwise pleasant surprises as "successful."
I'd really like to firm up my understanding of terms like "water discount" and "lye concentration." When I plan my soaps in future, I want to understand all the variables involved. I've mostly used others' recipes and soapcalc's default settings, because I really don't understand what is meant in this forum when someone says something like, "lower your lye concentration," or, "I'd try using medium water and see if that helps."
Could someone please direct me to a good article, or thread, where these terms are fully explained?
Thanks all!
 

topofmurrayhill

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Let me just anticipate one point of confusion. Almost nobody uses the term "lye" correctly, but Dunn does. When he says lye he is talking about the liquid solution, which could have any amount of caustic depending on the concentration (for instance 100 g of lye at 33% concentration is 33 g of caustic dissolved in 67 g of water). When he is referring to the actual dry caustic he says sodium hydroxide. Sodium hydroxide isn't lye.
 
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IrishLass

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Right here, silly!
Here is one our most recent threads that discusses this in detail:

http://www.soapmakingforum.com/showthread.php?t=53642


Very simply and straightforward, lye concentration refers to how concentrated/diluted your lye solution is- i.e., how much water was mixed with the lye. And as you will soon see, it is the best way of calculating (and discussing) the amount of water in one's batch.

The term 'Water Discount' on the other hand, is not as straightforward, and is the basis of much confusion. Sometimes it can mean the same thing as lye concentration, but many times it actually doesn't....... because it all depends on the soaper using the term and how they chose to calculate the water amount for their batch. .....i.e., did they choose to calculate their water amount based on their lye amount (aka a 'lye concentration'), or did they calculate their water amount based on the percent of oils in their formula?

More times than not, the term 'water discount' is tossed around willy nilly without any attempt to specify what the discount is based upon (the lye amount or the oils amount?), but it's very important to know which, because both methods of calculating water are very different from each other, and lead to much different results from each other.

Lye concentration (being based on utter predictability of lye) is very straightforward, and gives a soaper the ability to predict in a more consistently manner how their batches will proceed/turn out with the amount of water they are using, no matter what their formula; while on the other hand 'water based on oils %' is much more of a murky/nebulous thing because it's based on oils which as not as predictable as lye.

On page 2 of the link above, DeeAnna gives a great example of the unpredictability of basing water on oils % and why it's better to base water on the amount of lye used (lye concentration).


IrishLass :)
 

mzimm

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Thank you ToMH and IL so very much for your answers. From the article, forum thread, and your replies, you've perfectly understood my question. I was pretty sure my confusion was coming from hearing the terms misused, and from not knowing enough to know if they were misused or not.
I do enjoy Kevin Dunn's soap info. I just received his article from Wholesale Supplies Plus entitled "CHEMISTRY 101 ARTICLE: To Gel or Not To Gel" and that's what got me wanting to study up on these terms and understand them better. Was thinking about purchasing his book "Scientific Soapmaking" but got scared off by reviewers who said it was a book for chemistry students. Eek! I barely passed chemistry in HS. Might give it a try, though.
Let me just anticipate one point of confusion. Almost nobody uses the term "lye" correctly, but Dunn does. When he says lye he is talking about the liquid solution, which could have any amount of caustic depending on the concentration (for instance 100 g of lye at 33% concentration is 33 g of caustic dissolved in 67 g of water). When he is referring to the actual dry caustic he says sodium hydroxide. Sodium hydroxide isn't lye.
Thank you so much for pointing this out! This already clears up MUCH confusion.
 
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DeeAnna

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Bear in mind too that in historical and modern usage, "lye" can refer to sodium hydroxide solution OR potassium hydroxide solution. Since most people (including Kevin Dunn) make bar soap, "lye" usually means NaOH solution, but when the context leaves any doubt, it's smart to use the full chemical name.

I have and will still use the word "lye" to refer to the solid stuff as well as to the liquid solution, and I imagine I won't be the only one.
 

topofmurrayhill

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Yes, the word caustic was meant to cover either hydroxide. Since everyone has gotten used to referring to these caustics as lye, I don't expect it to change. However, Dunn prefers to stick with the actual definition of the word

lye [lahy]
noun, Chemistry
1.
a highly concentrated, aqueous solution of potassium hydroxide or sodium hydroxide.

My concern about confusion was that when one becomes accustomed to the usage you prefer, statements like this from the paper don't seem to make sense:

I added
water to the second bar equal to half the lye weight,
resulting in an effective lye concentration of 33.33%.
I added water to the third bar equal to the lye weight,
resulting in an effective lye concentration of 25%.
 

TeresaT

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Thank you ToMH and IL so very much for your answers. From the article, forum thread, and your replies, you've perfectly understood my question. I was pretty sure my confusion was coming from hearing the terms misused, and from not knowing enough to know if they were misused or not.
I do enjoy Kevin Dunn's soap info. I just received his article from Wholesale Supplies Plus entitled "CHEMISTRY 101 ARTICLE: To Gel or Not To Gel" and that's what got me wanting to study up on these terms and understand them better. Was thinking about purchasing his book "Scientific Soapmaking" but got scared off by reviewers who said it was a book for chemistry students. Eek! I barely passed chemistry in HS. Might give it a try, though.
Please do get Kevin Dunn's "Scientific Soapmaking." It was one of the first books I purchased that wasn't from a used bookstore. Much of it is over my head; however, I love that book and refer to it a lot. Of course, not nearly as much as I come here, but my nose is in that book quite a bit! It is written like a text book, but it isn't overwhelming. I read it through (eyes glazed over most of the time) to get an idea of what was in it. Then I went back and took a look at it a bit at a time and skipped what didn't interest me at that moment to concentrate on what did. I still do that.
 

mzimm

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Bear in mind too that in historical and modern usage, "lye" can refer to sodium hydroxide solution OR potassium hydroxide solution. Since most people (including Kevin Dunn) make bar soap, "lye" usually means NaOH solution, but when the context leaves any doubt, it's smart to use the full chemical name.
I'm glad ToMH pointed out KD's definition of the term, because it gave me pause when I read Dr. Dunn's article on "To Gel or Not To Gel." Understanding that it refers to the solution not the actual caustic used is an important distinction to get, especially when reading his work. As for other writers using the terms, I can now just remember to consider the context of what they're saying to determine what they mean: solution OR the caustic used, NaOH or KOH.
 

mzimm

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Please do get Kevin Dunn's "Scientific Soapmaking." .....
I read it through (eyes glazed over most of the time) to get an idea of what was in it. Then I went back and took a look at it a bit at a time and skipped what didn't interest me at that moment to concentrate on what did. I still do that.
LOL Teresa--- your learning style sounds just like mine! Thanks for the encouragement to take the plunge. I will!
 

SuzieOz

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When he says lye he is talking about the liquid solution, which could have any amount of caustic depending on the concentration (for instance 100 g of lye at 33% concentration is 33 g of caustic dissolved in 67 g of water).
^^^ THIS! ^^^ :D

Thank you so much topofmurrayhill - now I finally (really) get it :razz:
 

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