Moisturizing vs. less cleansing

[Sapo]

Quick question to see if my understanding of the subject is on point.

If we have a 100% CO soap and a 100% EVOO soap, we tend to call the EVOO more moisturizing/conditioning, and the CO more harsh.

But isn't this more a matter of...the EVOO simply being less stripping than the CO, in other words, less effective at cleansing, as no soap "truly" moisturizes, but rather cleans at different strenghts?

 

[shunt2011]

I don't call my soap moisturizing or conditioning. This has been discussed several times. It's a wash off product and is only meant to clean. The SF and oils used will determine how cleansing the soap will be.

 

[Lion Of Judah]

absolutely correct . high cleansing tends to strip away natural skin oils leaving a "squeaky " clean feeling while low cleansing tends to give you that "moisturizing " feeling.

ETA : shunt2011 got in ahead of me

 

[DeeAnna]

I use the words "mild" or "gentle" rather than "conditioning."

The only ingredient I've used in soap so far that leaves a faint but definite film on the skin is the lanolin I put in my last batch of shave soap. Very little of the lanolin saponifies, so I imagine that's probably the reason. So a soap with lanolin could be called moisturizing or protective, but I think that's an unusual exception, not the rule.

 

[FNG]

Think of the soap and the additives + SF as separate parts.

Soap being your "base", you will determine whether and to what degree it strips the skin of oils (cleansing over a value of 0) and what little bit of leftovers you'll have present in the way of unsaponifiable material. Lanolin and Jojoba are good examples that will leave more, but other oils like Shea and Cocoa butter will also have some "leftovers" to a lesser degree. These unsaponifiable bits can have some beneficial properties but it's usually such a small percentage of the soap that it is very difficult to see the effects.

A good rule of thumb I've found is the higher the SAP value, the more completely saponified the oil will be (less unsaponifiable material left over). For example:

Coconut oil NaOH SAP = 0.183
Jojoba oil NaOH SAP = 0.066

We can infer that for any equivalent quantity you will be left with more unsaponifiables in your soap using Jojoba oil vs Coconut oil. These materials can potentially have beneficial effects in the way of moisturizing or generally making the soap less harsh. Do your homework on each oil to understand each set of properties they bring to the table. Too much unsaponified material in your recipe and you won't have a proper soap :Kitten Love: (search the web for a 100% jojoba "soap" test and you'll get a good idea of what can happen)

The second thing is everything else that is not soap or unsaponified leftovers - Superfat and additives. I've found that these bits will give you more potential for beneficial properties that are easier for whomever is using it to detect. For example, adding sugar or glycerin to boost lather or using SFs and chelators to give a more soft, slick after-rinse feel.

 

[DeeAnna]

"...the higher the SAP value, the more completely saponified the oil will be (less unsaponifiable material left over)..."

With respect, this isn't really correct when you look closer at the chemistry that underlies saponification values.

The saponification value for most triglyceride fats -- coconut, lard, palm kernel, palm, tallow, the butters, olive and other liquid oils, etc. -- is more related to the size of the fat molecules in these fats, not to the unsaponifiable content. Unsaponifiable content in refined fats is fairly low -- a few percent at most -- so it really can't explain the wide range of sap values for the refined triglycerides. Unrefined fats such as unrefined shea and other unrefined butters do have higher unsaponifiable content, that is true, but that's not the only reason for the varying sap values of these fats.

Looking at the refined triglyceride fats -- The fat molecules in coconut oil are small because they are made up of short fatty acids (FAs) such as lauric, myristic, capric, and caprylic acids. That means there are many molecules of CO in each gram. Since each molecule of fat needs 3 molecules of alkali, more molecules per gram of CO => high sap value for CO. The average size of the fat molecules in lard are larger because they are based on palmitic, stearic, and oleic acids. That means there are fewer molecules of lard in each gram, less alkali is needed to saponify each gram of lard, and thus the sap value is smaller. In either case, the unsaponifiable content is low -- typically below 1%.

Moving to the unrefined triglyceride fats -- The sap value of shea at 0.128 is lower than lard at 0.142. But even if we're talking about unrefined shea at around 10% to 15% unsaponifiables vs. lard at around 1%, is the difference in sap value only due to unsaponifiables? Lard has more palmitic acid (a shorter chain fatty acid) thus lard will have more molecules per gram. Shea is primarily made of oleic and linoleic acids with little palmitic and smaller FAs, so shea has fewer molecules per gram. This difference in molecular size will contribute to the two fats having different sap values along with the difference in unsaponifiables.

Ingredients with little or no triglyceride fats by definition have a very high % of unsaponifiable materials. Lanolin, rosin, pine tar, and waxes such as Jojoba, beeswax, and carnauba come to mind. But since they're not triglyceride fats, comparing their "sap" values to those of the triglyceride fats is like comparing apples and oranges. We pretend they have a "sap" value because they do consume a small amount of NaOH or KOH, but they don't actually make useful soap even though they happen to consume lye.

 

[FNG]

"...the higher the SAP value, the more completely saponified the oil will be (less unsaponifiable material left over)..."

With respect, this isn't really correct when you look closer at the chemistry that underlies saponification values.

The saponification value for most triglyceride fats -- coconut, lard, palm kernel, palm, tallow, the butters, olive and other liquid oils, etc. -- is more related to the size of the fat molecules in these fats, not to the unsaponifiable content. Unsaponifiable content in refined fats is fairly low -- a few percent at most. Unrefined fats such as unrefined shea and other unrefined butters do have higher unsaponifiable content, that is true, but that's not the only reason nor is it the main reason for these fats having a lower sap value.

Looking at the refined triglyceride fats -- The fat molecules in coconut oil are small because they are made up of short fatty acids (FAs) such as lauric, myristic, capric, and caprylic acids. That means there are many molecules of CO in each gram. Since each molecule of fat needs a molecule of alkali, more molecules per gram of CO => high sap value for CO. The average size of the fat molecules in lard are larger because they are based on palmitic, stearic, and oleic acids. That means there are fewer molecules of lard in each gram, less alkali is needed to saponify each gram of lard, and thus the sap value is smaller. In either case, the unsaponifiable content is low -- typically below 1%.

Moving to the unrefined triglyceride fats -- The sap value of shea at 0.128 is lower than lard at 0.142. But even if we're talking about unrefined shea at upwards of 15% unsaponifiables vs. lard at around 1%, is the difference in sap value only due to unsaponifiables? Lard has far more palmitic acid (a shorter chain fatty acid) thus lard will have more molecules per gram. Shea is primarily made of oleic and linoleic acids with little palmitic and smaller FAs, thus shea has fewer molecules per gram and thus a lower sap value.

Ingredients with little or no triglyceride fats by definition have a very high % of unsaponifiable materials. That does mean they lower sap values, that is true. Lanolin, rosin, pine tar, and waxes such as Jojoba, beeswax, and carnauba come to mind. But since they're not triglyceride fats, comparing their "sap" values to those of the triglyceride fats is like comparing apples and oranges. We pretend they have a "sap" value because they do consume some NaOH or KOH, but they don't actually make useful soap even though they happen to consume lye.

Thanks for correcting me, DeeAnna. That actually makes sense.

I suppose it would only be useful in possibly identifying oddball ingredients like lanolin or jojoba since they have much, much lower SAP values but "normal" oils should be left out of such comparisons (keeps the apples with the apples). Even then, reading up on each oil/ingredient individually is probably the best course to be certain.