# Dual Lye Soap? What is this amazing concept?!



## mikvahnrose (Dec 24, 2016)

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


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## earlene (Dec 24, 2016)

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 (Dec 24, 2016)

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. :]


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## DeeAnna (Dec 24, 2016)

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 (Dec 24, 2016)

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!


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## Scooter (Dec 24, 2016)

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


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## DeeAnna (Dec 24, 2016)

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.



newbie said:


> 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.
> 
> ...



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.



Scooter said:


> ...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?


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## newbie (Dec 24, 2016)

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


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## mikvahnrose (Dec 25, 2016)

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 (Dec 25, 2016)

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


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## Susie (Dec 25, 2016)

mikvahnrose said:


> 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.


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## DeeAnna (Dec 25, 2016)

mikvahnrose said:


> ...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.



mikvahnrose said:


> 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.



Scooter said:


> ...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.


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## Susie (Dec 25, 2016)

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.


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## DeeAnna (Dec 25, 2016)

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.


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## The Efficacious Gentleman (Dec 25, 2016)

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


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## mikvahnrose (Dec 25, 2016)

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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## Susie (Dec 25, 2016)

mikvahnrose said:


> 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".


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## topofmurrayhill (Jan 1, 2017)

mikvahnrose said:


> 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 (Jan 1, 2017)

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:


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## mikvahnrose (Jan 1, 2017)

topofmurrayhill said:


> 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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## topofmurrayhill (Jan 1, 2017)

mikvahnrose said:


> Is there a way to test the purity of it? From what it sounds, people do estimates based on potential variables like humidity.



If you get Scientific Soapmaking by Kevin Dunn you can learn to do it the best way, but it will take some dedication to get into. If you have a knack for doing analytical procedures carefully, there's a simpler technique he demonstrated in this video:

http://greenerlifeclub.com/the-balancing-act-part-ii-presented-by-dr-kevin-dunn/

It's not especially difficult, but you'll need an accurate scale with a resolution of .01 g (two decimal places). You should understand how he's weighing off the scale instead of onto it, because that makes it easier to do correctly and allows you to use an affordable scale. If you needed a scale with that resolution that also had the capacity to hold the solution and the container, it would cost a lot of money. With the demonstrated technique you only need a scale that can accommodate a little cup of NaOH.


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## TeresaT (Jan 1, 2017)

newbie said:


> 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 decided to try this method and compare it to the amounts that the Soap Maker 3 spit out for the dual-lye (cream soap) recipe.  I used the 5% lye discount and 33.333% lye solution strength on all three recipes with 1000 grams of olive oil and no additives.   SoapMaker defaulted to 90% KOH purity, so I didn't change that, since I'm just playing with numbers.

*Dual-lye recipe calls for 123.61 grams NaOH,  7.23 grams KOH and 261.68 grams water*. 

Solid soap calls for 128.25 grams NaOH and 256.89 grams water.

Liquid soap calls for 199.86 grams KOH and 399.72 grams water.  

*Based on the solid and liquid recipes (and your math newbie), I would combine 121.84 grams (95%) NaOH with 9.99 grams (5%) KOH to make my dual-lye castile-ish soap.   
*
Rounding numbers, I'd use 2 grams less NaOH and 2 grams more KOH with the newbie math versus the SoapMaker math.  Will that difference have any affect in a 3# batch?  What about something larger like a 11# batch?

Newbie:  since you use master batch NaOH and master batched KOH, do you add any extra water or just use the master batched liquids?   

I was going to sit on the sofa and read a book; however, I think I'll grab the newly charged iPad and read these threads.

ETA:  I think this might call for some popcorn...


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## newbie (Jan 1, 2017)

Does cream soap use 95%/5%. Teresa? I'm not sure why there is the difference between the Soap Maker 3 numbers and mine because I've never used that program. My way seems logical but perhaps there is a flaw in my thinking somewhere. DeeAnna seemed to think my method would work but clearly your program and I are doing something different. Perhaps there is some difference in making liquid soap? I use soapcalc and simply change the NaOH button to 90% KOH and re-run the recipe to get the different lye numbers.

I do use my masterbatched solutions of both and just pour out double the caustic amount called for. The rest of the water I want is added after I have dissolved my sodium citrate into it; I use the balance of the water for any extra additives.


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## TeresaT (Jan 1, 2017)

newbie said:


> Does cream soap use 95%/5%. Teresa? I'm not sure why there is the difference between the Soap Maker 3 numbers and mine because I've never used that program. My way seems logical but perhaps there is a flaw in my thinking somewhere. DeeAnna seemed to think my method would work but clearly your program and I are doing something different. Perhaps there is some difference in making liquid soap? I use soapcalc and simply change the NaOH button to 90% KOH and re-run the recipe to get the different lye numbers.
> 
> I do use my masterbatched solutions of both and just pour out double the caustic amount called for. The rest of the water I want is added after I have dissolved my sodium citrate into it; I use the balance of the water for any extra additives.



Actually, the cream soap defaults to "1 part NaOH to 5 parts KOH" in the program with the KOH purity set at 90% and the lye discount at 6%.  I've never made cream soap before, so I just changed the NaOH to 95 parts and the KOH to 5 parts to give me 100 "parts" caustic.  I'll try SoapCalc and see what that comes out to.  I just thought it was interesting that the SoapMaker could create a recipe using both types of caustics.  

I wasn't sure if you actually did add the extra water called for in the recipe or if you just left it at the amount in the master batched lye solutions.    That's what I do with the extra liquid, too.  

I think I'll try two one pound batches tomorrow.  One using the SoapMaker "cream soap" figures and one from the SoapCalc figures.  I'll put colorants in the soaps to tell them apart and see if there is any difference (assuming when I run the number in SoapCalc they're different from SoapMaker).

ETA:  I ran the numbers in SoapCalc just now.  They're slightly different from SoapMaker.  I'm not sure why since the SAP values in both programs are the same.  That's kind of odd; I don't know what the difference in the math is.  However, I changed the values in SoapMaker for the NaOH to KOH to make them the give the same weights as the SoapCalc and ended up with 93% NaOH to 7% KOH.   I guess this just goes to show how much of a crap shoot these soap calculators actually are.  They are not _*exact*_ amounts because the SAP values are variables based on so many different things including growing conditions from crop to crop.  And the mathematical formulas used are apparently different even if the SAP values used are the same.(Math teachers are probably screaming at this!!)  Since I've actually figured out why there are differences in the calculations (to some degree), I'm just going to go with the SoapMaker since it is able to determine the "correct" amounts of NaOH and KOH in a dual-lye formula.   I've quit using SoapCalc since I started using SoapMaker, so I guess I'd better continue all of my soaps with the same calculator.   But I think it is very interesting that different calculators give different numbers; you'd think that they would all agree that 1+1=2.


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## penelopejane (Jan 2, 2017)

TeresaT said:


> you'd think that they would all agree that 1+1=2.



Soapmaker and soapcalc use different SAP values.
A soapmaker 33% recipe moves faster than a 33% soapcalc recipe. 
They are both "right". 

You just have to use one calculator and get used to what 33% means to your mix.


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## topofmurrayhill (Jan 2, 2017)

Different calculators might vary in their assumptions and defaults, but ultimately 1 + 1 does equal 2. There is a right answer for a given set of parameters (SAP values, lye discount and caustic purity).

I don't know if the raw calculations would be of use to anyone, but the approach I would probably take manually or programming it into a spreadsheet would be to figure out the SAP value of the recipe's oil mixture.

1000 g oil

10% CO
90% OO

.10 x NaOH SAP 0.183 = 0.0183
.90 x NaOH SAP 0.135 = 0.1215

Add them up and 0.1398 is the NaOH SAP value of your recipe. Multiply by 1.403 for the KOH SAP value, and then you can round them off if you like.

NaOH SAP = 0.140
KOH SAP = 0.196

Now it's simple. For 95/5 mixed caustic:

1000 x .95 x NaOH SAP 0.140 = 133 g NaOH
1000 x .05 x KOH SAP 0.196 = 9.8 g KOH

For lye discount, you can additionally multiply by the amount of oil you want to include in the lye calculation. For instance, for 5% lye discount just multiply the caustic amounts by .95. (The general formula is that you're multiplying by 1 - lye discount%, so 1 - .05 = .95)

133 x .95 = 126.4 g NaOH
9.8 x .95 = 9.3 g KOH

To incorporate your purity adjustments, just divide by the purity. For instance, assuming 100% NaOH and 90% KOH, we just adjust the KOH amount:

9.3 / .9 = 10.3 g KOH

Apart from any dumb arithmetic errors that I don't have time to find right now, that's how 1 + 1 = 2.


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## TeresaT (Jan 3, 2017)

TOMH, was that whole math thing for me?  You know my eyes just glazed over, right?

So...I made my dual lye soap last night using my SoapMaker formula. I thought I could dissolve the KOH in my 50% lye solution.  NOT.  I had to strain it out and add water to the crystals.  (I started to spell that "krystals." I've been living in Chattanooga too long.)  The olive oil actually traced much faster than normal (then again, maybe the eucalyptus mint FO is an accelerator).  I got it into my homemade mold and left it overnight.  I cut it tonight when I got home.  I'm glad I did, too, because that thing was a BRICK!!   I was barely able to get the cutter through it.  I thought I was going to bust every wire on my Bud cutter.  (Failed the zap test, though.  I didn't even have to zap test it.  I  popped the individual molds with bare hands and it was not a pleasant  feeling.  I put gloves on for the rest of the soap.)    I ended up with 15 bars averaging 8.55 oz each and a small 1.85 oz sliver.  That will be my tester.  In addition to the large mold, I poured, well plopped, 5 individual molds.  Three of those average 3.5 oz, one is 3 oz and the other is about 4.5 oz.  

These are photos of the soap still in the large mold and after I cut them.  I'm excited about the prospect of dual lye soap.  I'm going to try out my next recipe using dual lye and compare it to the standard NaOH only.


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## topofmurrayhill (Jan 3, 2017)

TeresaT said:


> TOMH, was that whole math thing for me?  You know my eyes just glazed over, right?



Of course they did. But I like to glaze your eyes over. And the secret is, if you felt like digging in you'd get it pretty easily. Your slogan should really be "sux-at-liking-math".


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## TeresaT (Jan 3, 2017)

topofmurrayhill said:


> Of course they did. But I like to glaze your eyes over. And the secret is, if you felt like digging in you'd get it pretty easily. Your slogan should really be "sux-at-liking-math".



Actually, I've written myself a note to look at this after I've had my pot of coffee tomorrow morning.


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