KOH accuracy in liquid bases with multiple fats

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Frank Deane

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Hi everyone! This is my first post to the forum and I'm very happy to share company with many veteran soap makers. I am a complete novice (I've made four batches of mild liquid soap in the last two months) and new to this space, so PLEASE forgive my ignorance as I build a working knowledge of the craft. I am presently fine-tuning a recipe for a wonderful mild liquid soap based on an old recipe for castile that I found on the internet. I like many of its properties, but want to experiment with a different blend of base oils: EVO (60%); Castor (10%); and Coconut (30%). I am using a specific brand of coconut oil and recently contacted the company to ask for the exact saponification value for the oil. They replied with the following message:

Please see the response from the lab: Unsaponifiable matter value of our unrefined coconut oil is tested to be between 0.1 to 0.2 percent by mass.


This isn't as straightforward as I was looking for, but I think it might still be highly useful in determining what my KOH alkaline solution proportion should be, relative to the percentage of this particular fat in my total base. However, I want to make sure that I've understood this correctly, because I feel that it's super important in terms of winding up with a neutral finished product/soap paste (hot method). What they're saying is that the oil contains 10% - 20% compounds that will not be saponified, given the assumption that the KOH is entirely pure (99.9%) -- RIGHT? Or am I missing something here? I think I would then have to reduce the percentage of KOH in solution to account for the inactive components in the base fat, per the info given by the manufacturer. Again, this is assuming the KOH is entirely pure. By contrast, if my KOH were only 90% pure, I am assuming I wouldn't need to make much of an adjustment if any at all. AM I understanding this concept correctly? Thank you all in advance!!!
 

DeeAnna

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Here's my CliffsNotes reply --

"...What they're saying is that the oil contains 10% - 20% compounds that will not be saponified..."

The supplier's info according to the quote states the unsaponifiable content is 0.1% to 0.2% by weight. I'm not sure where you're coming up with 10% to 20%.

Moving on -- The supplier has not answered your question with the info you need, but perhaps they misunderstood your question or they don't have that data. Regardless, be aware you will never get the EXACT saponification value of YOUR fat from the supplier. The sap value you get from any supplier is a representative, averaged number typical for their fat, allowing for normal variations typical for a natural product. If you feel the need for greater precision, you need to learn how to do the saponification value procedure and run it on the fat you have on hand.

That said, I believe you are waaaay overthinking this. Even if you have the exact sap values for every one of your fats and even if you know the exact purity of your KOH, you still need to use slightly more fat to drive the saponification reaction to completion and ensure all of the alkali has been reacted. That's just basic chemistry -- one reactant should be in slight excess to ensure the other reactant is fully consumed.

The practical advice to accomplish this -- use a slight superfat of 1% up to 3%, use the sap values in whatever soap recipe calculator you prefer to use, account for your actual KOH purity in the calculations, and make your soap. It doesn't need to be any more complicated than that.

If you need to correct for the purity of your KOH being less than 100% pure, then you can certainly should do so in your recipe calculations, but do not do this because you think you need to account for unsaponifiables. That would be fixing a problem that doesn't exist. Read on for more about this...

A little more about sap values -- The sap value you get from testing is the grams (or milligrams) of KOH (or NaOH) required to saponify 1 gram of the actual fat. The weight of KOH (or NaOH) in a saponification value is always corrected to 100% purity, by definition.

Saponification values are based on the results of testing samples of actual fats; they are not calculated theoretical values. By testing samples of the real fat, the effect of any unsaponifiable content (and also the effect of any components that consume alkali but don't saponify) is automatically included in the answer.

The scientific and industry convention is to report sap values based on KOH, but some handcrafted soap making books provide NaOH sap values instead. If the type of alkali is not specifically called out, you will need to figure it out and convert if required.

KOH sap value = 1.403 X NaOH sap value

NaOH sap value = KOH sap value / 1.403
 

Frank Deane

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Wow!!! DeeAnna -- thank you so much for that very informative and thorough answer. It all makes a lot more sense now. It's funny -- I was hoping I'd get a response from you, after I read one of your other comments. Thank you again!
 

DeeAnna

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Liquid soap making isn't greatly different than bar soap making, except it is more sensitive to the amount of superfat. So you can't ignore the KOH purity nor can you include a high % of superfat. But once you figure out what works well for your situation, liquid soap making is fun and fairly easy.

I hope my advice is helpful to you -- let us know how things work out.
 

shunt2011

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Also, you will never get a neutral product. Soap will always have a ph of 9-12 for the most part. Be it liquid or bar. And having 30% CO may be drying to many. You may want to read a couple of the LS threads for some awesome LS. Irishlass glycerin LS is so nice.
 

DeeAnna

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Even IL's clear LS recipe is 25% coconut -- http://www.soapmakingforum.com/showthread.php?p=428988 -- and it can be a little drying to my skin, especially in winter.

I think LS recipes are often higher in coconut than a similar bar soap because we want the liquid soap to build lather as fast as a bar soap, and LS doesn't usually lather as quickly nor as abundantly as bar soap in the time we spend washing our hands. Given the way most of us make and dilute LS to get a thick-ish, syrupy product, that means there is too much actual pure soap in the product than is needed to bubble well.

The extra coconut in many LS recipes compensates for this problem to some extent. I don't necessarily think that's the only way to solve the problem. Diluting the soap more is another solution, but a lot of people don't like a liquid soap when it's watery thin, unless the soap is used in a foamer dispenser.
 

Frank Deane

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Also, you will never get a neutral product. Soap will always have a ph of 9-12 for the most part. Be it liquid or bar. And having 30% CO may be drying to many. You may want to read a couple of the LS threads for some awesome LS. Irishlass glycerin LS is so nice.
Thank you for the insight -- much appreciated! I will also reconsider my percentage of coconut oil - moreso than lathering, I just wanted it to be an effective cleanser.
 

Frank Deane

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Even IL's clear LS recipe is 25% coconut -- http://www.soapmakingforum.com/showthread.php?p=428988 -- and it can be a little drying to my skin, especially in winter.

I think LS recipes are often higher in coconut than a similar bar soap because we want the liquid soap to build lather as fast as a bar soap, and LS doesn't usually lather as quickly nor as abundantly as bar soap in the time we spend washing our hands. Given the way most of us make and dilute LS to get a thick-ish, syrupy product, that means there is too much actual pure soap in the product than is needed to bubble well.

The extra coconut in many LS recipes compensates for this problem to some extent. I don't necessarily think that's the only way to solve the problem. Diluting the soap more is another solution, but a lot of people don't like a liquid soap when it's watery thin, unless the soap is used in a foamer dispenser.
Again, thank you for your insight and for being so thorough. I have another question specifically re superfatting of LS. I see that there is a category for superfat and fragrance/EO in the Soapcalc., but I'm confused about how this works. Not sure if this is true, but my understanding is that the superfat would be added after saponification and dilution and thus does not/is not meant to react with the lye solution. I understand that by default or intentionally adding more base fat the result would essentially be excess "superfat" in the end product, but when superfatting does the calc. also increase KOH? For instance, I was going to try superfatting my LS with 3%-5% extra oil and use Polysorbate 80 to emulsify the extra fat and essential oil added for scent. Please educate me? And apologies for being a bit long-winded.
 

DeeAnna

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Superfat is merely fat in excess of the amount that's strictly required to react with the alkali. It doesn't matter when you add the extra fat -- up front, after trace, whenever. It's all still superfat in the end.

You have it backwards, unless I'm misunderstanding your train of thought. The alkali weight goes DOWN as the superfat % goes up -- you are using less alkali so there is more fat left over in the finished soap.

...I was going to try superfatting my LS with 3%-5% extra oil and use Polysorbate 80 to emulsify the extra fat and essential oil added for scent....
If that's what you want to do, I encourage you to go for it. I gather you've read Irish Lass's tutorial about her cocoa-shea liquid soap, and that's as good as it gets -- I can't improve on that.
 

realtami

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Hi! Sorry if this is the wrong section, but I think i failed my liquid soap batch due to miscalculation of distilled water and KOH

This is my recipee ( soapcalc ) using 5% superfat

This is my third times making liquid soap using the EXACT recipe but with only 500 gr oils, my soap turns clear and the pH is around 9

This time I make about 1.5 kg batch

Water 570 gr
Lye 298,11 gr
Castor oil 75 gr
Coconut Oil 450 gr
Olive Pomace 750 gr
Cocoa Butter 225 gr

I realized in the end that I only use 283 gr of KOH ( minus 14 gr from the recipee) and 425 gr of water ( minus 145 gr from the recipee)

When I finished cooking it, I diluted tiny amount of it to distilled water and the solution is super cloudy with pH 8,8

Can something fix my liquid soap? Or should I dump it?

What about I make a lye solution using the remain of water and lye that I miscalculated?

145 gr of water + 14 gr oil KOH.

If I could, how to incorporate it into already cooked liquid soap?

Thank you so much if any of you can help me
 

DeeAnna

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No matter how I set this recipe up, it looks like you need more KOH than what your recipe calls for. So if you used even less KOH than the recipe, that's a problem.

I calculate a KOH weight of 337 grams at 3% superfat to 348 grams at 0% superfat assuming a 90% purity of the KOH. At 100% KOH purity, I get 304 g KOH at 3% SF to 313 g KOH at 0% SF. So you have not used enough KOH, and that is probably the reason why the soap is cloudy.

You can add the missing KOH and water to the paste. Just mix the KOH and water and carefully stir this lye solution into the paste until everything is wellmixed. Let the paste sit at room temperature for at least one or two days to give the KOH enough time to react with the fat. Cautiously test for zap.

Be aware that pH testing of soap requires a calibrated pH meter or high quality pH strips in a solution of 1% to 10% soap diluted in distilled water at room temperature. Any other method is going to give you inaccurate results - usually quite a bit lower than the true pH. And pH tells you nothing about the amount of excess alkali, if any -- the pH test is not accurate enough.

While you can certainly make liquid soap paste with the amount of water you calculated, I suggest using more water for easier processing. My liquid soap recipes are based on using a lye concentration of 25% (water:lye ratio of 3.0).

Your question is not directly related to the original topic of this thread, so fewer people are likely to see your request for help since it is hidden here, rather than out on its own as a new thread. In the future, you may want to create a new thread for a new question. That way you will get better advice from more people.
 
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realtami

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No matter how I set this recipe up, it looks like you need more KOH than what your recipe calls for. So if you used even less KOH than the recipe, that's a problem.

I calculate a KOH weight of 337 grams at 3% superfat to 348 grams at 0% superfat assuming a 90% purity of the KOH. At 100% KOH purity, I get 304 g KOH at 3% SF to 313 g KOH at 0% SF. So you have not used enough KOH, and that is probably the reason why the soap is cloudy.

You can add the missing KOH and water to the paste. Just mix the KOH and water and carefully stir this lye solution into the paste until everything is wellmixed. Let the paste sit at room temperature for at least one or two days to give the KOH enough time to react with the fat. Cautiously test for zap.

Be aware that pH testing of soap requires a calibrated pH meter or high quality pH strips in a solution of 1% to 10% soap diluted in distilled water at room temperature. Any other method is going to give you inaccurate results - usually quite a bit lower than the true pH. And pH tells you nothing about the amount of excess alkali, if any -- the pH test is not accurate enough.

While you can certainly make liquid soap paste with the amount of water you calculated, I suggest using more water for easier processing. My liquid soap recipes are based on using a lye concentration of 25% (water:lye ratio of 3.0).

Your question is not directly related to the original topic of this thread, so fewer people are likely to see your request for help since it is hidden here, rather than out on its own as a new thread. In the future, you may want to create a new thread for a new question. That way you will get better advice from more people.


Thank you so much for the info, I’m glad I didn’t toss out the soap paste in the garbage

So, I can make a lye solution using the missing KOH and distilled water, which is 14 gr KOH + 145 gr of distilled water and POUR it into my soap paste?

Or should I make the solution from the calculation of yours ( 3% superfat with 90% KOH purity) 337 grams-283 gram ( the amount of lye that I put in the beginning)

= 54 gram lye + 145 gr distilled water?



And what temperature my soap paste should be? Should I add the solution while cooking it again, or it can be pour on a cooled down soap paste?

I did the pH testing using calibrated pH meter.

Thank you so much for the reply, I am grateful
 

realtami

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No matter how I set this recipe up, it looks like you need more KOH than what your recipe calls for. So if you used even less KOH than the recipe, that's a problem.

I calculate a KOH weight of 337 grams at 3% superfat to 348 grams at 0% superfat assuming a 90% purity of the KOH. At 100% KOH purity, I get 304 g KOH at 3% SF to 313 g KOH at 0% SF. So you have not used enough KOH, and that is probably the reason why the soap is cloudy.

You can add the missing KOH and water to the paste. Just mix the KOH and water and carefully stir this lye solution into the paste until everything is wellmixed. Let the paste sit at room temperature for at least one or two days to give the KOH enough time to react with the fat. Cautiously test for zap.

Be aware that pH testing of soap requires a calibrated pH meter or high quality pH strips in a solution of 1% to 10% soap diluted in distilled water at room temperature. Any other method is going to give you inaccurate results - usually quite a bit lower than the true pH. And pH tells you nothing about the amount of excess alkali, if any -- the pH test is not accurate enough.

While you can certainly make liquid soap paste with the amount of water you calculated, I suggest using more water for easier processing. My liquid soap recipes are based on using a lye concentration of 25% (water:lye ratio of 3.0).

Your question is not directly related to the original topic of this thread, so fewer people are likely to see your request for help since it is hidden here, rather than out on its own as a new thread. In the future, you may want to create a new thread for a new question. That way you will get better advice from more people.

And about the testing the pH using 1 to 10% diluted soap, so I take about 15 gr of soap paste and diluted it on distilled water ( how many gr ? )

Thank you
 

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