need a chemists help with this recipe

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kc1ble

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Since I've gotten a few shaving soaps under my belt now, I found a recipe I would like to try but have no idea how the potash in the ingredients comes into play. First the ingredients on the label are:

Cocos Nucifera Oil, Tallow, Stearic Acid, Potassium Hydroxide, Sodium Hydroxide, Aqua, Potassium Carbonate, Parfum

So...lets go with

40% Coconut Oil
35% Tallow
25% Stearic Acid

60/40% KOH/NaOH

Instead of using a 60/40 split with my lyes, should it be a 3 way split with the K2CO3?


I also find it interesting that the KOH and NaOH are listed on the label before the water, meaning the amounts of these are greater than the water? Perhaps (more than likely) the label is not printed in order of quantity? I'm probably in over my head on this one as I can not find a calculator that includes potash and I am not smart enough to begin to figure it out. If you have any ideas on this, please give me your opinions, TIA.
 

galaxyMLP

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If this is a US label, it must be printed in order of decending quantity (unless it is an approved colorant or present in less than 1%). Since the ingredients are not listed as sodium/potassium oil-ate then it can't be the finished stuff in the product either. It's possible they made an error. Or, they may have made the product lye heavy and salted it out just by having excess lye. I would say an error would be more likely. You need at least as much water by weight as you do sodium and potassium hydroxide.

For the potassium carbonate: I have a theory I've been wanting to try for a while that I read in a soap manufacturing book. It says that the pure fatty acids can be saponifiyed with the carbonates (sodium or potassium carbonate) because those bases are not strong enough to react with triglycerides but are strong enough to react with the fatty acids themselves. It says that the only problem with that is that no fatty acids (at the time of the book writing) are pure enough that it makes it a viable option and you're always left with at least 10% triglyceride within the bulk of the fatty acid. In the case of stearic acid it would be as if 90% was stearic acid and 10% was the stearin triglyceride. I wonder if the company used potassium carbonate to react with the stearic acid in the recipe instead of the potassium hydroxide/sodium hydroxide. Why then would they choose to use potassium carbonate? Maybe it's cheaper than using potassium hydroxide in large quantities or, it could be safer for the operators when scaling up the production.

Edit: they may be using a steaming hot KOH/NaOH solution pumped by jets at really really high temperatures to saponifiy the oils. You can saponifiy things with water alone given enough heat. It would be steam driven saponification. They may be running their reaction at extremely high temperatures using a concentrated lye solution that is steaming hot and therefore uses less water to make the soap than would be traditionally be necessary. I'm just trying to think of a reason why water would be listed after the hydroxides.
 
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Susie

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What I know about shaving soap can fit safely on the head of a pin, with plenty of room left over, OK? Just so we understand that I have no real knowledge on this subject, LOL.

OK, my theory is that they did not list the water they mixed with the NaOH and KOH because there was no water left in the product after saponification. However, they perhaps needed to do a pH adjustment before adding the scent, so they used the potash, mixed with water, to do that. Since there was a higher possibility of water remaining at this stage, it got listed way down close to the end.
 

galaxyMLP

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According to what I just read they still have to list in descending order so what I say above still makes sense to me. I could be totally off base here but I thought I would throw it out there.

Btw, the potassium (hydroxide or carbonate) is added because it makes a more soluble soap which is better for initial lather build on a shaving soap. This is what I've read.
 

The Efficacious Gentleman

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Bear in mind, especially if this is a commercial product, they might be splitting the process some what. Again even more so if this is a milled soap.

Some people combine some of their fats with one lye and the other fats with another and then combine it, so as galaxy said - the potash might not even be used for saponification of anything at all.

Which soap is it? There is no need to be coy, but by leaving the name out it means we can't actually relate to the product and are shooting somewhat blind.
 

DeeAnna

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"...For the potassium carbonate: I have a theory I've been wanting to try for a while that I read in a soap manufacturing book. It says that the pure fatty acids can be saponifiyed with the carbonates (sodium or potassium carbonate) because those bases are not strong enough to react with triglycerides but are strong enough to react with the fatty acids themselves...."

Yes, this is a viable process. It looks to me like carbonate saponification of fatty acids was used on a modest scale in the early 1900s for some types of commercial soap making. The Soap Makers Manual by Edgar George Thomssen and also by WT Branndt and C Diete had short descriptions of this method.

But it is also true that you can use carbonates (sodium carbonate and sodium bicarbonate) to make soap directly from fats if you have the patience and enough heat. A fire extinguisher meant for kitchen fires is charged with carbonates that saponify fats into a foamy soap. Carbon dioxide is released in the process, which also acts to extinguish the fire. Carbonate saponification of fat is also the old process used to make soap from ash-based lye, if the soap maker didn't have lime to convert the carbonate lye to the more efficient hydroxide lye.
 

kc1ble

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I'll have to continue to do a little research on this subject when I have more time. Its a busy weekend for me so I've not much time to fool around with it now...to be continued...
 

The Efficacious Gentleman

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I would also look at the performance of the soap itself, rather than the recipe itself. Why duplicate a recipe when you can get the performance with something less complicated?
 

kc1ble

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I would also look at the performance of the soap itself, rather than the recipe itself. Why duplicate a recipe when you can get the performance with something less complicated?
Its more of a curiosity than anything else. Another method of making soap means a lot more reason to experiment. What's wrong with that?
 

The Efficacious Gentleman

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Its more of a curiosity than anything else. Another method of making soap means a lot more reason to experiment. What's wrong with that?


Nothing at all - all I was saying was that if the performance of the soap itself was the goal then the method is not always so important. But as you say, you are after some experiments which is something else entirely
 

Susie

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We're all big ones for experiments, when we have the time and energy to do so! Please keep us posted?
 

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