Dual Lye Soap? What is this amazing concept?!

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mikvahnrose

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I just read another thread not to far down from this one.

Dual...lye...soap. What!! So many questions!

1) What does it do? I see people use it for shaving cream soap. Is it possible to have the Koh kept at low percentages to have a still firm bar of body soap with fluffier bubbles? (i have low coconut oil recipe)

2) what is a good ratio to achieve this? 90% naoh 10% koh? Higher? Lower?

3)Does the Koh make the soap not last as long?

4) can you masterbatch dual lye soap. and water discount?

5) is there a good calculator for this!

All this time i thought only liquid soap and solid soap could be created. Not a blend. Neato! My brain in churning. Sorry for so many questions. Been here for a while, and not once come across this process, twas intriguing
 

earlene

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More people with more experience can answer with more detail and background, but here's my understanding and experience so far.

Better lather and bubbles; less slime in Castile Soap (and other high oleic soaps).

Yes, I have some very very hard bars of Castile soap made with dual lye. In fact, they are actually harder than soap with the same recipe except for the dual lye even though they are less than half the age of the older soap. (Castile made 15 months ago, versus Castile made 6 months ago.)

A good ratio is 95% NaOH and 5% KOH. I did try 10% KOH, but personally didn't felt that it was too soft. However, they haven't cured for long, so that may change. Although I have read that at least one soaper here uses 10% KOH.

I don't know the answer to question #3. I don't have any soap that I feel doesn't last long enough, so in my gut I say no. But my opinion is subjective, not objective.

As far as masterbatching, do you mean the lye? I masterbatch NaOH, but not KOH. I don't use KOH as often as NaOH, so I don't feel that it's a big deal, although it would be interesting to learn more if anyone has done this. You can still masterbatch your oils in the usual way. (I don't masterbatch my oils, but many do.

Yes, you can do a water discount. I have made Dual Lye soap using a 40% Lye Concentration, no problem. See this thread with photos of my soap made this way. See post #15 in that thread.

The lye calculator I use for Dual Lye soaps is Soapee here: http://soapee.com/calculator. I find it easier to use than the MMS lye calculator at the Sage. I have used it, but not so much since finding Soapee. (I learned about Soapee here at SMF.)

There are several threads here at SMF that address using dual lye for bar soap. I don't think I saved them all, in fact I may not even have found them all, but I read several when I was doing my research. There is also another site that I found useful, I think I saved it. I'll list some of them below. Some links I saved don't work anymore, unfortunately (not an SMF link, though.)


http://curious-soapmaker.com/making-100-olive-oil-soap-why-it-should-be-avoided-by-beginners.html
http://classicbells.com/soap/dualLye.html
http://www.soapmakingforum.com/showthread.php?t=28493
http://www.soapmakingforum.com/showthread.php?t=42922
http://www.soapmakingforum.com/showthread.php?t=61550
http://www.soapmakingforum.com/showthread.php?t=59747
http://www.soapmakingforum.com/showthread.php?t=32706

I know there are a few more, but it's getting pretty late, so this will have to do for now.
 
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mikvahnrose

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Wow thank you Earlene, you were above and beyond helpful! Answering *almost all* of my questions lol. Soap for me doesn't last that long in my house either.

Thank you for the links! Good reads!

And hopefully someone here may have enough knowledge of master-batching dual lye. :]
 

DeeAnna

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Sure you can masterbatch an NaOH-KOH mixture. Remember the 5% KOH we're talking about is 5% KOH molecules in the mixture, not 5% KOH weight. KOH molecules are chunky fellows compared to NaOH molecules -- one KOH weighs 1.403 times one NaOH. That's why the 1.403 is used in this relationship:

Wt KOH = 1.403 X (Wt NaOH) / (% Purity NaOH) X 100 X (% KOH desired in the masterbatch) / 100 / (% Purity KOH) X 100

The relationship can be made less complicated by doing all the math on the numbers first --
Wt KOH = 140.3 X (Wt NaOH) / (% Purity NaOH) X (% KOH in masterbatch) / (% Purity KOH)

An example: NaOH is 97% pure, KOH is 84% pure, and you want to use 800 g NaOH. You want to make a masterbatch solution that is 95% NaOH molecules and 5% KOH molecules. How much KOH is needed by weight?

Wt KOH = 140.3 X 800 / 97 X 5 / 84 = 68.9 g

Can you see how the KOH weight is more than 5% of the NaOH weight? Very important point.

Edit: The way the online calcs handle lye solution concentration is to calculate it based on the total actual weight of alkali. This is technically not correct, but it is the way it's done. So to calculate the water weight for this amount of alkali, you would do this:

Alkali wt = NaOH wt + KOH wt
Water wt for 50% solution = Alkali wt

For the example given above:
Alkali wt = 800 + 68.9 = 868.9 g
Water wt for 50% solution = 868.9 g
 
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newbie

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I've tried this just recently but I am doing the math differently.

I put my recipe and batch size in soap calc (or other soap calculator) and find the amount of lye needed for that batch and then multiply it by 0.95 and use that amount of lye.

I then rerun the same recipe but for KOH (I use the 90% pure button) and find the amount needed for the whole batch. Then I multiply that amount by 0.05 and use that amount of KOH.

Since I can pop over to the calculator on my computer, I can get amounts needed with minimal fuss.

I have both sodium hydroxide and KOH master batched so I just pour out double the weights I've calculated.

I think that achieves the same result- or at least I hope it does!
 

Scooter

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I have been following these threads pretty closely and will probably make some 5% KOH OO soap after the holidays.

My one question is...does the 5% KOH trick improve on, in any discernible way, a bastile that is 72% OO, 5% Castor with the rest in CO? Or, for that matter, have people found 5% KOH helpful in any other type of soap besides 100% OO?

Thanks for all the tips.

Scooter
 

DeeAnna

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Yep, that works too, Newbie. You're letting the calc do the math, and that's fine.

Main differences between your method and mine --

The equation in my post is independent of any soap recipe so it can be used just to make a masterbatch of lye solution. For example, if I have a container that I know holds X amount of 50% lye solution, then you can just use that to figure out the KOH weight for an arbitrary total amount of NaOH.

For example, I have a 1 L (1000 mL) container. I know the container can hold roughly 1500 grams of 50% NaOH solution. Half of that is 750 grams of actual alkali. I want some extra room in the container for the added KOH and also room to safely stir the solution without splashing. I might make a masterbatch of lye solution based on 650 to 700 grams of NaOH. I'd figure the KOH for that amount of NaOH. That would be my "recipe" for a masterbatch lye solution to fill that particular container.

The relationship I shared also includes a correction for NaOH purity. The calcs don't take NaOH purity into account. But that's not a deal killer -- all of our calculations are estimates anyways, even mine. Hopefully close estimates, but estimates nonetheless.

I've tried this just recently but I am doing the math differently.

I put my recipe and batch size in soap calc (or other soap calculator) and find the amount of lye needed for that batch and then multiply it by 0.95 and use that amount of lye.

I then rerun the same recipe but for KOH (I use the 90% pure button) and find the amount needed for the whole batch. Then I multiply that amount by 0.05 and use that amount of KOH.

Since I can pop over to the calculator on my computer, I can get amounts needed with minimal fuss.

I have both sodium hydroxide and KOH master batched so I just pour out double the weights I've calculated.

I think that achieves the same result- or at least I hope it does!
Have you read any of the threads listed in Earlene's post, Scooter? Using KOH in various recipes been discussed at length. Short answer is, yes, it does, although my opinion is the more CO, the less benefit the KOH will have.

...My one question is...does the 5% KOH trick improve on, in any discernible way, a bastile ...? Or, for that matter, have people found 5% KOH helpful in any other type of soap besides 100% OO?
 

newbie

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Ah yes, I see, DeeAnna. I missed that you were calculating to master batch this ratio of the alkali.
 

mikvahnrose

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Thank you Deeana for the math formula to the masterbatch. Just need to spend some time working it on paper so i don't have any mistakes. Never used Koh, so that will be a bit of a learning curve. Luckily i was always good at math :]

You said multiply by the purity of the lye, Naoh and Koh.
Aren't you suppose to buy 100% pure sodium hydroxide? Does Koh not come in 100% purity as well?

And the question regarding 800 grams of NaOH. What do you mean, i want use 800 grams of Naoh? Or are you saying i (Have) 800 grams total of naoh (to make my masterbatch) and you want to (Add) koh to the formula to the total formula equal 95% naoh? Sorry if my question may be unclear.
 
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Scooter

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Thanks DeeAnna for the masterbatch calculations! But for those of us who just make a little bit of soap, at infrequent intervals, for our own households, the soapee calculator (at http://soapee.com/calculator) should be adequate, correct?

Thanks,

Scooter
 

Susie

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You said multiply by the purity of the lye, Naoh and Koh.
Aren't you suppose to buy 100% pure sodium hydroxide? Does Koh not come in 100% purity as well?
Not DeeAnna, but I might be able to shed some light onto this question. No, KOH does not come with 100% purity. That does not mean that something "bad" is in there, just that different manufacturers know that their KOH has absorbed a certain amount of moisture by the time it is packaged. I buy from Essential Depot that says their KOH is 95% pure. I live in a humid environment, so by the time I open the bottle and use it, it is closer to 90% purity. That is what I use on the soaping calculator, and it works fine for me. I never get separating soap, which is what will happen if there is too little KOH for the amount of oil.
 

DeeAnna

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...You said multiply by the purity of the lye, Naoh and Koh. Aren't you suppose to buy 100% pure sodium hydroxide? Does Koh not come in 100% purity as well?
What Susie said.

NaOH and KOH are never 100% pure. From my supplier, my NaOH is around 95% pure and my KOH happens to be about that too. Read the info on your supplier's website or ask them for the purity of the alkali you are using.

Depending on how you store and handle these chemicals, that purity will gradually drop from exposure to carbon dioxide and moisture in the air. That means YOU also have a big effect on the purity of these chemicals as you use them.

And the question regarding 800 grams of NaOH. What do you mean, i want use 800 grams of Naoh? Or are you saying i (Have) 800 grams total of naoh (to make my masterbatch) and you want to (Add) koh to the formula to the total formula equal 95% naoh?...
Your second sentence is the correct one. IF you wanted to make a masterbatch solution that contains 800 grams of NaOH, how much KOH would you need? Just an example to show how the equation could be used, nothing more.

...for those of us who just make a little bit of soap, at infrequent intervals, for our own households, the soapee calculator ... should be adequate, correct?
As Newbie and I have already been discussing, yes, you can use Soapee to calculate the KOH and NaOH needed for a single batch of soap. No one needs to make a masterbatch of anything, ever.
 

Susie

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I never masterbatch. I prefer to make my lye solution fresh each time I soap. I am a hobby soaper, only, so I don't need a lot. If I made soap to sell, I would masterbatch. It would make sense to do it once a week or month.
 

DeeAnna

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I didn't masterbatch lye until this past year. I sell a little soap here and there, but selling is not why I masterbatch. I like using a masterbatched lye solution mainly because I view making the lye solution as the most tedious and unappealing part of the soap making process, so masterbatching is my way of minimizing the misery. :) I don't make a lot of lye solution at a time -- just enough for 3-4 batches.

So far, I have not done an NaOH-KOH masterbatch. First off, I just started using 5% KOH in my bar soap recipes earlier this year so I'm still in the stage of evaluating what I think of it. Second, I only use a few grams of KOH per batch as well, and dry KOH is so much easier to measure and dissolve, so it's just not that big of a deal.

If I had a serious soap biz, I probably would include the KOH in my masterbatched lye solution, but using dry KOH is not that big of a deal to me. As always, however, my way ain't the only way -- YMMV. :)
 

The Efficacious Gentleman

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I also found that it greatly reduced my time required to make a batch. Now that I have a better place to make a large batch of lye, it's something I will certainly be doing again. Because I also make shaving soaps, I'll likely make a smaller bottle of 50% strength KOH rather than having a mixed solution, so I'll also just use that in there
 

mikvahnrose

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Wow, i didnt know sodium hydroxide wasnt 100% pure. From other groups, people always stressed to get "100%" lye. So i got mine from essential depot from their suggestions.

I never put forth much thought into it after that, but i am taking it that you mean it is 100% lye, just not 100% lye strength. That is good info to know.

I looked back at the essential depot site, and it says their lye strength is 96% minimum. So in the calculations i would put around 96%.
 

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Wow, i didnt know sodium hydroxide wasnt 100% pure. From other groups, people always stressed to get "100%" lye. So i got mine from essential depot from their suggestions.

I never put forth much thought into it after that, but i am taking it that you mean it is 100% lye, just not 100% lye strength. That is good info to know.

I looked back at the essential depot site, and it says their lye strength is 96% minimum. So in the calculations i would put around 96%.
You want to be sure to buy "100% lye", meaning there are no other ingredients listed on the container. Just be aware that that does not necessarily mean that your NaOH/KOH is "100% pure".
 

topofmurrayhill

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I looked back at the essential depot site, and it says their lye strength is 96% minimum. So in the calculations i would put around 96%.
That's not actually the right conclusion. 96% is the minimum, but it's probably higher than that when you receive it. By assuming 96% you'll be using more caustic soda than you really wanted to, decreasing your superfat or potentially going a bit lye heavy under certain circumstances. Basically you would be erring in the wrong direction.

In one public demonstration, Essential Depot NaOH tested 98.3%.

So, the correct procedure is not to assume the minimum purity you expect the caustic to have. In fact, there's no official number you should use unless you test it. Otherwise you can be conservative and assume 100%, or you can take a guess. This applies to NaOH. KOH has similar but different issues.
 
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penelopejane

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I only started masterbatching recently and it makes soaping a joy. So easy just to shake the container and pour out the right amount of lye mixture.

Great time and hassle saver. I am totally sold on masterbatching now. Thanks to all the patient maths people on the forum. It's not that the maths is difficult but it needs a good explanation and notes to get it right. :mrgreen:
 

mikvahnrose

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In fact, there's no official number you should use unless you test it. Otherwise you can be conservative and assume 100%, or you can take a guess. This applies to NaOH. KOH has similar but different issues.
Is there a way to test the purity of it? From what it sounds, people do estimates based on potential variables like humidity.
 

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