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 Soap Making Forum > Castile 95%NaOH 5%KOH calculations help
06-27-2016, 12:37 AM   #1
earlene
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Castile 95%NaOH 5%KOH calculations help

Quote:
 Originally Posted by DeeAnna To make a soapmaker's classic castile that lathers nicely, lasts a long time, and only requires a 4-6 week cure --> use 100% olive oil, whatever lye solution concentration you prefer, the usual 5% superfat (lye discount), and a blend of 95% NaOH and 5% KOH (potassium hydroxide).
Quote:
 Originally Posted by DeeAnna The KOH makes the soap more soluble in water. Thsi means the usual stringy oleic soap gel doesn't form as easily with a KOH-NaOH castile as it does with a castile made with NaOH only. I won't debate the "cure faster" issue -- all I will say is if you want to make a true castile (100% olive oil) and would like it to last a long enough time, make lots of nice lather, and be mild to the skin after a more typical 4-6 week cure, then try using the mixed lyes.
I really want to try this, but I am having a very hard time trying to adapt my [50% lye] masterbatch to say, a 40% lye concentration, particularly with the added KOH.

Using the advanced search I have been unable to find any answers to this question. It doesn't mean they are not here, but I just cannot find them.

I think I can do the calculations for a 40% concentration easily enough with just NaOH, but with a 5% KOH and 95% NaOH, how would I do this? I am at somewhat of a loss. Do I use the NaOH water and ignore the KOH water recommendations? Or is there a formula for figuring out how much water for the KOH separate from the amount needed for the NaOH, thus having to add the two together?

Well this is how far I have gotten so far:

95% NaOH for this 32 ounces of OO = 110.9 grams
5% KOH = 9.1 grams (per Soapee) Or is it 8.1 grams (I get 8.1 if I use the 0.713 number as the divisor in this post)

That's about as far as I get, because I don't know where to go with the water.

Soapee says to use 179.9 grams of water total. Okay, so if I do that, then here's what I will do with my 50% masterbatch:

221.8 grams of 50% Lye solution
69 grams of additional distilled water
9.1 grams of KOH (per Soapee) BUT other calculations lead me to 8.1 grams (1.403 as a multiplier or 0.713 as a divisor)

Both MMS & SummerBeeMeadow also come up with 8.1 grams KOH, so I am thinking 8.1 grams is correct and not the 9.1 I get in Soapee (or maybe that's because the KOH is set at 90% purity in Soapee?)

Which of these numbers correct for the KOH?

Is the additional water amount correct, and how does one determine that for a mixed lye soap?

~ ~ ~ ~
Also at one point I think I found a post where someone (don't remember who, but I think it was one of the more sciene-minded members) posted a little chart about how to figure out how much water to add to a 50% lye pre-mix (masterbatch) solution to come up with respective concentrations. I believe it listed them like for 40% add, for 35% add, like that. Anyway I can't find it now and I thought I bookmarked it. So perhaps it was my imagination.

06-27-2016, 01:34 AM   #2
TheDragonGirl
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Usually I do mine as a ratio of lye to water so like 1:1 1:1.5 1:2 1:3, if I'm not mistaken you want something like 1:1.5 for the concentration you're considering, so it would be the full weight of both of the lyes together X 1.5, and that's your water.

Edit: pardon, so basically you would calculate how much is already in there via 1:1 on the first lye, then subtract that from the new number, and add whats left to your solution

Last edited by TheDragonGirl; 06-27-2016 at 01:37 AM.

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06-27-2016, 07:31 AM   #3
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I would also look at making two 50% solutions, based on the amount of each lye needed, then just use extra water to get it to a 40% solution water amount based purely on the NaOH. With just 5% KOH, the difference in actual grams of water won't be massive
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06-27-2016, 10:45 AM   #4
ngian

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Well DeeAnna has motivated me too these days with the Dual Lye Castile, and I'm planning to make one with some old olive oil (that I want to get rid of) and actually add a little of coconut.

Here is my recipe:

Olive: 95% - 475gr
Coconut: 5% - 25gr
Water (38% Lye Concentration): 114,8gr
NaOH 95%: 64.8gr (purity 98%)
KOH 5%: 5,5gr - (purity 85%)
Lye Discount: 2%

This is what an excel file that I have gave me, which has the ability to set purities for both NaOH and KOH in a dual alkali recipe.

The logic with the water amount is to take the amount of NaOH and find the water based on your lye concentration, then do the same with KOH to find its amount of water needed based again on your lye concentration, and finally add those two water amounts.

So in my above recipe:
NaOH 64,8gr x 1,632 = 105,75gr
KOH 5,5gr x 1.632 = 8,97gr
Total water: ~144,72gr
(1:1,632 is the ratio of water based in the 38% lye concentration)

As far as it concerns your case you will need
221.8 grams of 50% NaOH Lye solution and add to that 55,45gr of water in order to have a total of 110,9gr NaOH and 166.35gr of water (1:1.5 ratio)
and then add KOH 9,1gr with 13.65gr water.

Hope I helped you a little, and I also hope to find some time this week.

Last edited by ngian; 06-27-2016 at 03:04 PM.

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06-27-2016, 12:56 PM   #5
DeeAnna

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You say MMS and SBM call for 8.1 g KOH and Soapee calls for 9.1 g KOH. This is most likely due to different assumptions for KOH purity and differences in the saponification values in each calculator.

SBM is set to about 95% purity and Soapee is at 90% purity. I'll have to check MMS again and confirm what purity their calc is set to nowadays.

I think most people most of the time are getting more reliable results when using 90% purity, so I'd recommend the KOH weight based on 90% purity (Soapee's answer).

***

Total water for the batch is based on the total weight of both lyes. Your math is correct in your first post for the amount of extra water you need to use in addition to the water in your 50% NaOH masterbatch to end up with a 40% lye concentration.

***

If you want to calculate the total water required based on the lye weights, just to double check, here is how to do it --

Total lye weight = NaOH weight + KOH weight
Total water weight = (Total lye weight) * 100 / (Lye concentration percent) - (Total lye weight)

Using your numbers from Soapee --

Lye concentration percent = 40
Total lye weight = 110.9 + 9.1 = 120 g
Total water weight = 120 * 100 / 40 - 120 = 180 g

You said "...Soapee says to use 179.9 grams of water total...." So my answer is a fraction of a gram off of Soapee's number, but it's close enough.

Last edited by DeeAnna; 06-27-2016 at 12:59 PM.

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06-27-2016, 02:43 PM   #6
earlene
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Thank you all for taking the time to answer. That helps a lot. I see everyone comes up with the same answer, so that is reassuring!

I like having the equations to work with as back-up. Thank you for providing the equation, DeeAnna. I have saved your response for future reference because I can see that the equation will come in handy. I have also saved the recipe & will be making it today.

Thank you again, everyone!

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06-27-2016, 03:27 PM   #7
earlene
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Quote:
 Originally Posted by The Efficacious Gentleman I would also look at making two 50% solutions, based on the amount of each lye needed, then just use extra water to get it to a 40% solution water amount based purely on the NaOH. With just 5% KOH, the difference in actual grams of water won't be massive
Gentleman, I had thought of that. I am not sure I am ready to start keeping a KOH masterbatch solution, though. Just having both dry lye solutions in the same bucket for storage has me feeling more cautious (a good thing, of course). If I put a KOH pre-mix solution into the mix I fear I may one day use the wrong solution to make soap.

Well, I could do the same as I did for the dry solution. I bought some kiddy bandaids & put them on the tops of the KOH to differentiate them from the NaOH. I know, kiddy bandaids!?! Well, a small package cost a lot less than Brightly colored Duck Tape, which was what I was going to do. I don't have any small children around, so it seemed to be just as efficient a method for differentiating the two different lyes from each other. Anyway, if I decide to make a KOH masterbatch, I could use the same kiddy bandaid ID method on the top of the bottles. I'm pretty sure that would work for me.

Still, I am not sure how often I would be using the KOH. Has anyone used the dual lye method with soaps other than castile? I see ngian is looking to do a bastile with dual lye.

Quote:
 Originally Posted by ngian Well DeeAnna has motivated me too these days with the Dual Lye Castile, and I'm planning to make one with some old olive oil (that I want to get rid of) and actually add a little of coconut. Here is my recipe: Olive: 95% - 475gr Coconut: 5% - 25gr Water (38% Lye Concentration): 114,8gr NaOH 95%: 64.8gr (purity 98%) KOH 5%: 5,5gr - (purity 85%) Lye Discount: 2%
This sounds very interesting. I do hope you post your results. I wonder if how noticeable a difference there is from the traditional single lye soap vs the dual lye soap with this recipe. Are you going to do a control batch, too for comparison?

06-27-2016, 03:30 PM   #8
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I meant just simply taking your required weight of KOH and mixing it with enough water to dissolve it, same with the NaOH, then add more water - not making a massive amount of 50% to keep for other times
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06-27-2016, 03:31 PM   #9
ngian

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Quote:
 Originally Posted by earlene This sounds very interesting. I do hope you post your results. I wonder if how noticeable a difference there is from the traditional single lye soap vs the dual lye soap with this recipe. Are you going to do a control batch, too for comparison?
You are right, I must do a control recipe with NaOH only so as to estimate the benefits of dual alkali soap...

06-27-2016, 03:42 PM   #10
Arimara
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Quote:
 Originally Posted by ngian Well DeeAnna has motivated me too these days with the Dual Lye Castile, and I'm planning to make one with some old olive oil (that I want to get rid of) and actually add a little of coconut. Here is my recipe: Olive: 95% - 475gr Coconut: 5% - 25gr Water (38% Lye Concentration): 114,8gr NaOH 95%: 64.8gr (purity 98%) KOH 5%: 5,5gr - (purity 85%) Lye Discount: 2% This is what an excel file that I have gave me, which has the ability to set purities for both NaOH and KOH in a dual alkali recipe. The logic with the water amount is to take the amount of NaOH and find the water based on your lye concentration, then do the same with KOH to find its amount of water needed based again on your lye concentration, and finally add those two water amounts. So in my above recipe: NaOH 64,8gr x 1,632 = 105,75gr KOH 5,5gr x 1.632 = 8,97gr Total water: ~144,72gr (1:1,632 is the ratio of water based in the 38% lye concentration) As far as it concerns your case you will need 221.8 grams of 50% NaOH Lye solution and add to that 55,45gr of water in order to have a total of 110,9gr NaOH and 166.35gr of water (1:1.5 ratio) and then add KOH 9,1gr with 13.65gr water. Hope I helped you a little, and I also hope to find some time this week.
I'm going to warn you to be careful and be prepared for a possible soap-on-a-stick. I made a batch of 100% avocado oil soap using this method and it REALLY (can't stress that enough) did not need to be stickblended. It went to thick trace in a few seconds and that was for both -SF and 0 SF. I haven't tried with a 5% superfat and I did note that it took only slightly longer with to trace with the 0% (really a few seconds longer).

So, be careful and be prepared.