How much Sodium Carbonate to use for soapmaking?

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SimpleSoaper

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I want to try making a 100% olive oil soap using sodium carbonate as the "lye". Can anyone give me a rough estimate (or better yet a specific amount) of how much to use per unit EVOO? I'll be salting this out, so some excess is ok. I just have no idea how much to use and don't want to go too far overboard. Thanks.
 

DeeAnna

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How many days do you plan to boil the soap?

I'm really not joking. It will be a very slow process if you want to use sodium carbonate to make soap from fats. That's why when people learned to use slaked lime to convert the carbonate alkali to the hydroxide, they never looked back.

If you really really want to use carbonates, then saponify fatty acids instead of fats. It's the splitting of the triglyceride that is hard for a carbonate alkali to do.

Or stick with the hydroxides and just get 'er done. :)
 

TheStat

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How many days do you plan to boil the soap?

I'm really not joking. It will be a very slow process if you want to use sodium carbonate to make soap from fats. That's why when people learned to use slaked lime to convert the carbonate alkali to the hydroxide, they never looked back.

If you really really want to use carbonates, then saponify fatty acids instead of fats. It's the splitting of the triglyceride that is hard for a carbonate alkali to do.

Or stick with the hydroxides and just get 'er done. :)
Will there be any difference in the soap if you use sodium carbonate vs lye?
 

DeeAnna

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"Lye" is the generic term for any alkali solution that can be used to make soap. Sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, etc. -- these solutions can all be called "lye." It's best to name the actual chemical you're talking about when there's any doubt.

To restate your question - You wonder will there be any difference in the soap if you use sodium carbonate versus using sodium hydroxide?

No difference. The carbonate reacts to carbon dioxide gas during the reaction, so the soap batter will get foamy/fizzy and can boil over easier. But when all is said and done, the finished soap is going to be the sodium salts of fatty acids regardless of which alkali you use.
 

TheStat

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"Lye" is the generic term for any alkali solution that can be used to make soap. Sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, etc. -- these solutions can all be called "lye." It's best to name the actual chemical you're talking about when there's any doubt.

To restate your question - You wonder will there be any difference in the soap if you use sodium carbonate versus using sodium hydroxide?

No difference. The carbonate reacts to carbon dioxide gas during the reaction, so the soap batter will get foamy/fizzy and can boil over easier. But when all is said and done, the finished soap is going to be the sodium salts of fatty acids regardless of which alkali you use.
Would 8-10 hours of cook time suffice when making soap with sodium carbonate?
 
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SimpleSoaper

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I'm trying to make a Marseilles "homage" soap, and the hydroxides just aren't gettin' 'er done for me. One traditional Greek olive oil soapmaker (Patounis) says he finds 5 days to be the optimal cook time, so I'm guessing he's using sodium carbonate. That's the max cook time I will shoot for, more or less. I just don't know how much sodium carbonate to use. All of the recipes I've found convert it into NaOH before adding the oil.
 

DeeAnna

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I wouldn't make the assumption he's using sodium carbonate. I really wouldn't. It more likely he is doing a traditional "boiled" process, which takes days to complete even using sodium hydroxide. A boiled soap is done with low-shear mixers or hand stirring, often lower NaOH concentrations than we soapers on SMF normally use especially with olive oil, and several charges of lye during the saponification time. The soap may or may not be "salted out" with actual salt -- it may instead be salted-out with lye solution. The final soap has no superfat to a slight lye excess.
 

Raf

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Does anyone knows the amount of salt and water require to salt the soap out, I mean to separate the soap in glycerin, and to get rid of the excess of caustica soda and water? too?
 

DeeAnna

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In a boiled method, the soap is already mixed with an excess of water, so you don't add more -- that would be counterproductive. The addition of salt is not a precise thing. The amount will vary depending on the amount of water and the fatty acids in the soap. The addition is done by eye -- you watch the texture change.

And you do know you can salt-out soap using NaOH, right? You don't have to use salt.

Here's how to salt-out soap scraps: https://classicbells.com/soap/saltOutTut.html It's basically the same process as salting-out a boiled soap.
 

Raf

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Thanks a million! This is the information I was looking for, ... the classicbells explanation is so precise, cool !
 
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