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Dual Lye Soap? What is this amazing concept?!

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topofmurrayhill

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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.
 

TeresaT

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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!
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...
 

newbie

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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.
 

TeresaT

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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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topofmurrayhill

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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.
 

TeresaT

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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.

IMG_0895.jpeg

IMG_0896.jpeg
 

TeresaT

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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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