One-step Vs Two-step Soap

[Anglezarke]

I was reading this article , which states:

While most often the one-step triglyceride reaction with lye is considered, there is also a two-step saponification reaction. In the two-step reaction, steam hydrolysis of the triglyceride yields carboxylic acid (rather than its salt) and glycerol. In the second step of the process, alkali neutralizes the fatty acid to produce soap.

The two-step process is slower, but the advantage of the process is that it allows for purification of the fatty acids and thus a higher quality soap.

Can someone please explain what this means and are we CP/HPers producing one or two step, and if it's the former, how can we try to create the latter?

Thanks!

 

[DeeAnna]

Handcrafted soap makers are doing a one-step saponification process to make soap.

Hydrolysis of fats, as used in this context, is not something that can be done by the average hobby soap maker, unless you have industrial-grade equipment in your kitchen. This is the process of splitting a triglyceride (fat) apart with the use of heat and water (steam). The result of hydrolyzing fat is a mixture of various fatty acids, glycerin, unsaponifiable content, and other impurities. After hydrolysis, the glycerin and other content are separated from the fatty acids.

The mixture of various fatty acids (FAs) can be further separated into various types of FAs if desired. This is done by cooling the FAs until the higher melt point FAs crystallize and then separating the solid FAs and liquid FAs. The fatty acids, whether used as-is or separated, can then be used to make soap or other products. You'll sometimes see "coconut acids" which means a mixture of all FAs that are in coconut oil. Or you might see "stearic acid" which means a specific FA that has been separated from other FAs.

The statement that the resulting soap made with fatty acids is more pure is misleading in that it implies the "more pure" soap is "more better." Soap made this way won't have the glycerin that comes from saponification. It will not have the unsaponifiable content provided by some fats (avocado and shea being 2 examples). But whether this type of soap is actually better is a judgement call. Certainly commercial soap manufacturers may think so, but the desire to deliberately keep those "impurities" in the soap is one of the motivations for people to make handcrafted soap.

 

[Anglezarke]

Thank you very much for the detailed response. That was an education! People often think pure=natural, and the two-step certainly isn't the latter. I can fully understand why the commercial makers would go that route, but it does go against what I suspect most home soapers are trying to achieve.

 

[DeeAnna]

"...People often think pure=natural, and the two-step certainly isn't the latter...."

Think about the following and then you may want to reconsider the value judgement you've made here --

In the one step process, an incredibly strong alkali -- one that doesn't exist in nature (sodium hydroxide) and requires quite a bit of energy to produce -- is normally used to saponify the fat.

In the two step method, heat and water are used to split the fats, but then a milder alkali -- such as sodium carbonate that can be found in nature -- can be used to saponify the fatty acids.

I can't see how a person can really make any value judgement -- how is one "less natural" than the other? It's just chemistry.

A handcrafted soap maker can achieve results roughly comparable to the two step method by salting-out the soap after it has been made. Again, this "more pure" soap isn't necessarily "more better" ... it's just different.

There may be times when a salted out soap or a soap made from fatty acids is the only way to produce a particular product. So it's hard for me to say any of this soap is more or less "natural" regardless of how the soap is made.

 

[Anglezarke]

I guess the ashes of birch mixed with animal fats is the simplicity / romance of one-step lye soap.

But I must admit I do think the mass-produced, 25-pence-a-bar Palmolive Naturals Moisture Olive is a lovely bar. And no doubt it's two-step.

Sodium Palmate , Aqua, Sodium Tallowate, Sodium Palm Kernelate, Talc, Glycerin, Stearic Acid, Sodium Chloride, Parfum, Pentasodium Pentetate, Pentaerithrityl Tetra-di-t-butyl Hydroxyhydrocinnamate, Olea Europeae Fruit Oil, Aloe Barbadensis Leaf Juice Powder, Sine Adipe Lac, Benzyl Salicylate, Butylphenyl Methylpropional, Citronellol, Coumarin, Limonene, Linalool, CI 77891, CI 475, CI 6157.

 

[DeeAnna]

Actually, Palmolive is a "boiled" soap. It's a type of "one step" soap if you will, but not a soapmaking process that most handcrafted soap makers do, simply because it's more tedious than the HP or CP processes. The stearic acid is not soap -- it's stearic acid used as a superfat to ensure there is no excess alkalinity.