What really makes coconut oil stripping ?

[Elise]

I have been wondering for quite a while now, maybe someone here could help me with that question.
Is saponified coconut oil "in essence" more efficient in binding to fats/sebum and is what makes it harsher, or is it just that it is more soluble and so we get more soap faster when using it and so get washed more efficiently ?
Is the bubbling properties of coconut oil due to its solubility ? And if so, do other ways to make more of a bubbly soap (sugar, aloe, castor oil...) mean you inevitably also increase the cleaning value ?

 

[AliOop]

It is the high amount of lauric and myristic fatty acids that make saponified CO more cleansing.

Other methods of increasing solubility (sugar, aloe, starches) don't increase the cleansing value, just the solubility.

Castor oil does not actually increase bubbles; it only supports them (makes them last longer). It does not contain cleansing FAs and thus doesn't increase the cleansing nature of the soap.

 

[Mobjack Bay]

Based on my current understanding of soap chemistry and how soap interacts with skin, I think the answers to your questions are actually quite complex because mildness depends on skin characteristics, how the fatty acid soaps interact with the skin barrier, how fatty acid soaps behave when mixed with water and probably other factors I'm not aware of.

From my own limited research I'll wager that the nature of the soap micelles formed by different fatty acid soaps plays a role in perceived soap mildness just as it does for the mildness of detergents. The lauric and myristic fatty acids that predominate in coconut oil will want to form small micelles, which will maximize the cleansing ability of the soap. I imagine that adding longer chain fatty acids or sugars, starches, clays, etc. alters the structure of the micelles (makes them bigger and/or more irregular) and would lead to less cleansing, e.g. per unit weight of a soap bar used.

I am also aware the fatty acid chain length and saturation affect how FAs interact with the skin barrier but I don't know the science well enough to speculate on how those interactions might affect the mildness of soap.

 

[Elise]

Thank you @Mobjack Bay and @AliOop !
So lauric and myristic fatty acids become something that is different in nature than what the other fatty acids turn into when saponified.
I would love to read more on the different kind of micelles and how additives like sugar affects them or the fatty acids. Do you have by any chance readings you could point me to ? I don't find anything when searching the internet in french, and I'm find that I'm not very good at searching in english (I guess I don't use the right keywords).

 

[Mobjack Bay]

Just to clarify - during saponification, lauric and myristic fatty acids are turning into soap, just like the other fatty acids. And, as far as I am aware, all soap makes micelles. The shorter FA chains make shorter soap molecules, which I'm suggesting will affect the size of the micelles they form. I have not read anything specific about how sugar interacts with soap micelles - I was speculating.

Most of what I know about micelles comes from reading posts on the Swift Crafty Monkey website about detergents and how mixing detergents affects mildness. When different types of detergents are mixed, the micelles grow in size and the shapes become more irregular. This results in milder cleansing. The SCM website is behind a paywall. Using Google Scholar I can find articles like this one, but they are pretty difficult to read and absorb.

 

[Elise]

Sure, they all make soap, but since they rend different properties I'm wondering how it is explained by chemistry.
I'll have a look at that and see what I can understand from it.
Thank you again !

 

[Mobjack Bay]

Sure, they all make soap, but since they rend different properties I'm wondering how it is explained by chemistry.
I'll have a look at that and see what I can understand from it.
Thank you again !

Keep us posted! I'm always interested in why things work the way they do in soap making, but it's often difficult to find the answers.

For more ideas about how physical or chemical effects of additives like castor and sugar affect bubbling, read this thread (also includes a fun horsey hijack).

 

[DeeAnna]

It's not only the lauric acid in a coconut oil soap that creates the harshness, but it's also the presence of shorter fatty acids (FAs) that most soap recipe calcs don't tell you about.

Most soap recipe calcs only "know" about the main fatty acids that are found in most soap making fats -- lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, and ricinoleic. They don't account for fatty acids that aren't not one of these 8 main soap making FAs.

Capric and caprylic acids are two medium-chain fatty acids present in coconut oil (as well as in babassu, palm kernel, etc.) You won't, however, see these FAs in the soap recipe calcs I know of.

These FAs, plus their slightly longer cousin lauric acid, are capable of not only emulsifying and removing natural ~fats~ from the skin, but they can also bind with and strip off natural ~proteins~ from the surface of the skin. This combined stripping effect is why soap high in lauric, capric, and caprylic acids can be very drying and irritating to the skin.

I don't recommend making soap from fractionated coconut oil (aka "liquid" coconut oil) and MCT (medium-chain triglycerides). Capric and caprylic acids are the main fatty acids in these oils. They're great used as-is on skin, but not great when converted into soap.

More info: https://www.nutritionadvance.com/fractionated-coconut-oil/

 

[Elise]

Keep us posted! I'm always interested in why things work the way they do in soap making, but it's often difficult to find the answers.

For more ideas about how physical or chemical effects of additives like castor and sugar affect bubbling, read this thread (which more or less survived a horsey hijack).

I enjoyed reading your thread ! For both the chemical informations and the hijack

It's not only the lauric acid in a coconut oil soap that creates the harshness, but it's also the presence of shorter fatty acids (FAs) that most soap recipe calcs don't tell you about.

Most soap recipe calcs only "know" about the main fatty acids that are found in most soap making fats -- lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, and ricinoleic. They don't account for fatty acids that aren't not one of these 8 main soap making FAs.

Capric and caprylic acids are two medium-chain fatty acids present in coconut oil (as well as in babassu, palm kernel, etc.) You won't, however, see these FAs in the soap recipe calcs I know of.

These FAs, plus their slightly longer cousin lauric acid, are capable of not only emulsifying and removing natural ~fats~ from the skin, but they can also bind with and strip off natural ~proteins~ from the surface of the skin. This combined stripping effect is why soap high in lauric, capric, and caprylic acids can be very drying and irritating to the skin.

I don't recommend making soap from fractionated coconut oil (aka "liquid" coconut oil) and MCT (medium-chain triglycerides). Capric and caprylic acids are the main fatty acids in these oils. They're great used as-is on skin, but not great when converted into soap.

More info: https://www.nutritionadvance.com/fractionated-coconut-oil/

Thank you @DeeAnna ! I didn't even know there were other FA than the ones appearing in soap calcs !
While reading the thread recommended by Mobjack Bay in their previous post, I ended up on your website. I realised I read some of it last year but forgot a lot of what I learned. I'm glad I read it again, you provide very good informations that I believe I should know before inquiring deeper.

 

[DeeAnna]

Here are the 8 most common fatty acids (FAs) in soap -- the most typical FAs found in many soap recipe calcs.

The first word (ex: Lauric) is the name of the FA. The ratio after the name is the number of carbon atoms in the FA followed by the number of double bonds (ex: 12:0). A saturated FA has zero double bonds (lauric through stearic). A mono-unsaturated fatty acid has one double bond (oleic, ricinoleic). A poly-unsaturated fat has 2 or more double bonds (linoleic, linolenic)

Fatty acid name carbon atoms : double bonds
Lauric 12:0
Myristic 14:0
Palmitic 16:0
Stearic 18:0
Oleic 18:1
Ricinoleic 18:1
Linoleic 18:2
Linolenic 18:3

The second list (below) shows even more FAs that I've tracked. As you can see there are some shorter FAs with fewer carbon atoms than the "big 8", quite a few FAs with even more carbon atoms than the "big 8", and several with carbon backbones that are similar but with differing numbers of double bonds.

So there's a whole laundry list of FAs that are omitted in the soap recipe calcs. To be fair, many of these "exotic" FAs aren't found at all in common soap making fats or are present only in small amounts -- perhaps a percent or two at most.

I'd say the biggest errors come from omitting butyric, caprylic, and capric acids.. Butyric is present in milkfat/butterfat/ghee. Caprylic and capric are present in all of the typical "cleansing" and "bubbly" fats such as coconut, palm kernel, and babassu and derivatives such as FCO and MCT. The net effect of including these 3 FAs in a recipe calc would be to increase the "cleansing" and "bubbly" numbers.

And problems can definitely crop up when people want to make soap out of exotic fats that contain unusual FAs in higher percentages. They take the soap calc info for these fats at face value and then wonder why they're getting unexpected results.

Fatty acid name carbon atoms : double bonds
Proprionic 3:0
Butyric 4:0 (odoriferous FA found in milkfat (aka butterfat, ghee))
Valeric 5:0
Caproic 6:0
Caprylic 8:0 (predominant fatty acid in FCO)
Capric 10:0 (ditto)
Lauric 12:0
Myristic 14:0
Myristoleic 14:1
Palmitic 16:0
Palmitoleic 16:1
Sapienic 16:1
Margaric 17:0
Stearic 18:0
Oleic 18:1
Elaidic 18:1
Ricinoleic 18:1
Vaccenic 18:1
Linoleic 18:2
Linoelaidic 18:2
a-Linolenic 18:3
g-Linolenic 18:3
Octadecatretraenoic 18:4
Arachidic 20:0
Eicosenoic 20:1
Gondoic 20:1
Eicosadienoic 20:2
Arachidonic 20:4
Eicosapentaenoic 20:5
Behenic 22:0
Erucic 22:1 (fatty acid found in rapeseed oil)
Brassidic 22:1
Docosenoic 22:1
Isoerucic 22:1
Docosadienoic 22:2
Docosahexaenoic 22:6
Lignoceric 24:0
Cerotic 26:0

 

[Elise]

@DeeAnna, I'm amazed by the quality of all the content that you post here on this forum. I'm always glad when I stumble upon one of your posts when browsing old or recent thread because I know it will be both honest and documented answers.
I hope you get all the recognition you deserve for the time you spend sharing your knowledge. At least I, am very grateful.

 

[DeeAnna]

@Elise -- Thank you! I'm glad my stuff is helpful to you