What makes the fatty salts different?

I'm trying to understand what we get after saponification and why some are considered an emollient and all the mysteries of the universe while I'm at it.

So, why are they different? And on the same note, why is sodium XX-ate different than postassium xx-ate. Do they behave differently? Why?

To sum it up, it's all in the chemistry (literally). From this thread, DeeAnna explains why NaOH is used for bar soaps and KOH is used for liquid soaps. As for the properties you get from using varying oils, it all comes down to the molecular make up of the oil and the resulting properties.

I am not a chemist nor am gifted in that field, so I can only tell you that the emollient you get is just the result of the saponification process. During a chemical reaction (caused by a lye-liquid solution), the fatty molecules brake down and the elements merge with whatever will make it complete... I guess in the most compatible way. Hence, fatty acid + lye solution = soapy salt & glycerine (our emollient). As for why it may be considered an emollient, it's probably because of the glycerine's help to maintain moisture in our skin.

Please forgive me if I sound crazy, I just need to sleep. I hope DeeAnna can answer your question better. Good Night.

LunaSkye said:

To sum it up, it's all in the chemistry (literally). From this thread, DeeAnna explains why NaOH is used for bar soaps and KOH is used for liquid soaps. As for the properties you get from using varying oils, it all comes down to the molecular make up of the oil and the resulting properties.

I am not a chemist nor am gifted in that field, so I can only tell you that the emollient you get is just the result of the saponification process. During a chemical reaction (caused by a lye-liquid solution), the fatty molecules brake down and the elements merge with whatever will make it complete... I guess in the most compatible way. Hence, fatty acid + lye solution = soapy salt & glycerine (our emollient). As for why it may be considered an emollient, it's probably because of the glycerine's help to maintain moisture in our skin.

Please forgive me if I sound crazy, I just need to sleep. I hope DeeAnna can answer your question better. Good Night.

Click to expand...

i think you did a great job

Yes, I knew all that, that wasn't my question. Let me try to rephrase it:

What is it that makes the conditioning fatty acids conditioning once they're turned into soap? Why do they behave differently than the other ones?

I'll apologize for repeating the beginner's lesson. Check out this site. It gives the overview of the fatty acid types. You can also find a few more sites on the yahoo search engine.

@Lion of Judah: Thanks.

I give up.

I think the answer is pretty much "they just are" - DeeAnna put a great post about the different kinds of oils and the properties in the soaps and all that. The question of why they are like that is not answered, I'm afraid

Okay, WSP -- you have asked a good question, so don't give up. I'm not entirely sure I have a good answer, because I've been searching for info on this issue for some time without a lot of luck. Mostly what I've found is the "common wisdom" that we read on soapcalc and other popular soaping sides. While this info is helpful in an empirical way, I have not been able to uncover much, if any, of the science to back up this common understanding.

Here's my first stab at a preliminary answer. Bear in mind this is very much a work in progress, so don't hold my feet to the fire if my point of view evolves with time.

***

I'm ambivalent about describing soap as moisturizing, emollient, conditioning, etc. All those words are used to describe something that soothes, protects, and softens the skin. My current opinion is that the superfat in a soap can be moisturizing, emollient, conditioning, etc., but I question how the soap itself can be.

What I do know is that soap dissolved in water has the ability to emulsify fats and thus dissolve greasy soil. Call it "cleaning" for short. The ability to clean is related to the soap's ability to dissolve in water (solubility) and to its ability to emulsify fats.

Solubility is partly related to the type of ion that is attached to the fatty acid to make the soap. These ions include ammonium (NH3), potassium (K), sodium (Na), lithium (Li), magnesium (Mg), calcium (Ca), barium (B), lead (Pb), mercury (Hg), and others. I've listed them in order of how soluble their soap is in water -- from high solubility (ammonium, potassium) to mostly or completely insoluble (magnesium, calcium, barium, lead, mercury).

Add the word "hydroxide" after the words ammonium, potassium, and sodium and you will get the name of the most common soaping lyes. Any particular soap recipe can be changed just by using a different lye. A soap made with sodium hydroxide (NaOH) will be a firm bar soap and the least soluble and lowest lathering. If you make the same recipe except use either potassium hydroxide (KOH) or ammonium hydroxide (NH3OH), the resulting soap will be softer, ranging from a paste to liquid in form. The soap will also be more soluble, and lather more freely. By using a mix of two or more of these lyes, you can adjust the relative solubility, hardness, and lathering ability of the finished soap.

* Side note: Concentrated ammonium hydroxide cannot be safely used as a lye for making handcrafted soap, because it is extremely hazardous to work with -- far more dangerous than KOH or NaOH. Some soap recipes include "household ammonia" which is a dilute solution (5%, if I remember correctly) of ammonia in water. That is just not concentrated enough to use as 100% of the lye, so recipes with household ammonia must also enough KOH or NaOH for complete saponification. *

In addition to the choice of lye, the fatty acids in the recipe will affect the solubility and the cleansing ability of a soap. Some soaps are very soluble and are also very efficient emulsifiers -- cleaning to the point of leaving the skin dry and uncomfortable. These would be soaps made with short chain, saturated fatty acids such as myristic, lauric, capric, butyric, etc.

Other soaps are also relatively soluble, but they are not quite so efficient at cleaning because they are less efficient at emulsifying fats. These soaps tend to leave more of the skin's oils intact, so they are considered more "emollient" or "conditioning". These would be the soaps with mono- and poly-unsaturated fatty acids -- oleic, linoleic, and linoleic.

Still more soaps are relatively INsoluble and moderate to low on cleansing efficiency -- these would be soaps with longer chain, saturated fatty acids such as stearic and palmitic.

It's my guess at this point that the soaps that are considered more "conditioning" are the ones that are more INsoluble and/or less efficient emulsifiers. They simply leave more of the skin's oils intact. Whether they actually leave a film of "conditioning stuff" behind on the skin after the suds are rinsed off (not counting any superfat) -- that I cannot say. I'm still looking into this.

See also: http://www.soapmakingforum.com/showthread.php?t=48845

DeeAnna said:

It's my guess at this point that the soaps that are considered more "conditioning" are the ones that are more INsoluble ...

Click to expand...

DeeAnna, aren't unsaturated fatty acids the most soluble AND the most conditioning at the same time? I mean their sodium salts...

Sometimes asking for the "why" is harder than explaining it.

Thanks DeeAnna for the schooling, and thank you other Lee for asking the question!

wetshavingproducts; I think another factor (besides what DeeAnna explained) is that oil/butters have a certain percentage of unsaponifiables that aren't turned into soap, and depending on your superfat levels, they will remain behind on the skin.

I've made a recipe with co 20%/palm 40%/oo 35%/castor 5 and compared it with the same recipe with co/palm/shea/oo/castor (replaced half of palm with shea). Shea has one of the highest percentages of unsaponifiables. To those who have tried it, they described the shea bar as being more "moisturizing".

"...aren't unsaturated fatty acids the most soluble AND the most conditioning at the same time..."

You needed to include the rest of my sentence to keep the full meaning.

"...the soaps that are considered more "conditioning" are the ones that are more INsoluble and/or less efficient emulsifiers..."

Less efficient soaps are ones from the unsaturated fatty acids. INsoluble soaps are the ones from longer chain saturated fatty acids.

"...Sometimes asking for the "why" is harder than explaining it...."

Uh, okaaaaayyyy, then YOU spend the several hours writing the answer to the next geeky soap science question!

I'm just joshing you, Lee.

But honestly, I debated whether to get involved in the discussion, because it is difficult for me to write a response that I don't have enough hard facts on which to base my answer. I'm not interested in perpetuating "what is commonly understood to be true" about soaping unless it's backed up with science, not assumptions or wishful thinking.

Bear in mind that the primary fatty acids in palm are palmitic and oleic. The primary fatty acids in shea are stearic and oleic. Simply shifting the fatty acid profile to less palmitic and more stearic will make the skin feel of the shea soap seem "more conditioning".

lenarenee said:

wetshavingproducts; I think another factor (besides what DeeAnna explained) is that oil/butters have a certain percentage of unsaponifiables that aren't turned into soap, and depending on your superfat levels, they will remain behind on the skin.

Click to expand...

Yes, but that's a separate issue since the jist of the issue I'm concerned with is that the basic fatty acids are colloquially attributed with these properties.

So, the colloquial wisdom is that oleic acid (if purified) saponified, is a conditioning soap salt. Unsaponifiables should be, and usually are, treated as an additive and discussed separately.

DeeAnna said:

Uh, okaaaaayyyy, then YOU spend the several hours writing the answer to the next geeky soap science question!

Click to expand...

Yes but see you KNOW the answer. As we've proven, getting the question out in a way people understand it is challenging.

I'm sitting here waiting for some Stearic to melt and going through some e-books. Nice afternoon!

Deanna,
Thanks for responding.

I too have been spending too many hours thinking about this issue. However, I don't have that chemistry background to help me with the thinking. So, I have no idea what's going on at a molecular level.

But so far, here's what I've deduced:
The conditioning value is based off of either:
1) The fatty salt is actually an emollient and stays on the skin to help moisturize & condition. (a la Soapcalc); or
2) The fatty salt is not an emollient and simply cleanses less. This explanation would just put the salts on a scale of cleansi-ness.

At first I thought that #1 couldn't be true because soap is soap, it has a hydrophillic and phobic end and would therefore combine with both and rinse off with water.

Which left #2 which is a tidy explanation, but seems incomplete because at least some people actually say their skin feels softer than before they washed it. So there has to be some conditioning property.

But after further thought, it might be possible that both are true.

Evidence:
We know that even though soap is a rinse off product, some fragrance oils stay behind. If we over fragrance, even more fragrance stays on the skin or is absorbed or something.

After rinsing, there is some residue left on the skin that we can feel.

Which still leaves the question of:
Why would the fatty salt be an emollient anyway?

Yup, all good questions. Unfortunately I don't have good answers. We'll just have to keep picking away at this....

Very interesting thread but as a newbie my head is spinning! Thank you posters for sharing your knowledge. I have a lot of reading to do.

Desederata said:

Very interesting thread but as a newbie my head is spinning! Thank you posters for sharing your knowledge. I have a lot of reading to do.

Click to expand...

This post is 4 years old.

Better late than never!

"Conditioning" is calculated by adding Ricinoleic + Oleic + Linolinic + Linoleic fatty acids . How's that for meaningless information? The calculation does NOT take into account what if any SF value there is so the unsaponified oils have nothing to do with the value.