Clarification on Superfatting from a Chemistry Perspective ??

Soapmaking Forum

Help Support Soapmaking Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Gaspar Navarrete

Well-Known Member
Joined
Mar 5, 2014
Messages
116
Reaction score
19
Location
Trujillo, Peru & Montgomery Cnty, MD
Hello everyone,

Can I get elucidation on this superfatting question from a chemistry point of view ?

From a helppage in SoapCalc, I learned that one end of the soap molecule grabs onto a water molecule, and the other end grabs onto a dirt molecule. When one washes the soap away, the dirt molecule is pulled away from the skin and is washed away as well

My question is this:
============

When one superfats, one is adding oil to a big mass of soap molecules. Wouldn't the soap molecules immediately grab onto the molecules of the oil ? When one washes the soap away with water, how come all the superfat oil molecules (or most of them) don't get washed away along with the water & soap ?

Obviously the superfat oil manages to positively affect the skin. So how does it survive the "grab" of the soap molecules ?

Thanks.
 
Last edited:
Soap is a salt. The atoms that comprise the salt are bonded together. The atoms that make up the superfatted oils are not part of these salt "molecules" and therefore would not interact with them.

When I used to teach chemistry I used to tell my students that once atoms are in a bond they're happy. They have all the electrons they need (the whole reason why they bond) and don't care about anything else. So for our application, the soap molecules are "happy". The oils that make up the superfat are like the third wheel.

DeeAnna, please correct me if I'm wrong anywhere. It's been awhile since I taught chemistry. Haha!
 
"...Obviously the superfat oil manages to positively affect the skin...."

Okay, first off, tell me specifically how you know that to be true.

"...one end of the soap molecule grabs onto a water molecule, and the other end grabs onto a dirt molecule...."

Not exactly. One end grabs onto a polar molecule and the other end grabs onto a non-polar molecule. It usually happens that the polar molecule is water and the nonpolar molecule is fat. Often the fat is attached to some type of undesirable object (aka "dirt"), but it can just be fat floating around in the water or a fatty coating on the skin or fabric.

"...Wouldn't the soap molecules immediately grab onto the molecules of the oil?

Yes, pretty much.

"...When one washes the soap away with water, how come all the superfat oil molecules (or most of them) don't get washed away along with the water & soap ?..."

Most probably do, Gaspar.
 
"...Wouldn't the soap molecules immediately grab onto the molecules of the oil?

Yes, pretty much.

"...When one washes the soap away with water, how come all the superfat oil molecules (or most of them) don't get washed away along with the water & soap ?..."

Most probably do, Gaspar.

If there is more oil (AKA superfat) then there is soap molecules to grab onto the oil doesn't that mean there will be oils left on the skin? Isn't this the main reason why high SF helps people with really dry skin?
 
"...Obviously the superfat oil manages to positively affect the skin...."

Okay, first off, tell me specifically how you know that to be true.

. . . because soapmakers like to add superfat oils to their soaps. They talk about the different benefits that each oil brings. As we know there a lists of oils and the properties that each oil contributes to the soap. So I assume the above is true.

If there is more oil (AKA superfat) then there is soap molecules to grab onto the oil doesn't that mean there will be oils left on the skin? Isn't this the main reason why high SF helps people with really dry skin?

but the superfat oil is usually a small percentage of the whole recipe. The oils in the rest of the recipe have all been saponified into soap molecules. How could there be more superfat oil molecules than soap molecules ?
 
".... . . because soapmakers like to add superfat oils to their soaps. They talk about the different benefits that each oil brings. As we know there a lists of oils and the properties that each oil contributes to the soap. So I assume the above is true...."

Hmmm... A healthy skepticism is always good when reading opinions and theories. Here are two alternate hypotheses that many other soapmakers, including me, subscribe to -- Superfat reduces the cleaning ability of the soap so it doesn't have the negative effect of stripping the skin of its natural oils. And superfat ensures there is no excess alkali in the soap after saponification is complete.
 
Last edited:
Here are two alternate hypotheses that many other soapmakers, including me, subscribe to -- Superfat reduces the cleaning ability of the soap so it doesn't have the negative effect of stripping the skin of its natural oils. And superfat ensures there is no excess alkali in the soap after saponification is complete.

If I read your post correctly, the hypothesis is that the properties of the soap (like moisturizing, hardness, lather, cleansing, etc.) isn't going to change appreciably when one adds a superfatting oil at the end of the HP cook :Kitten Love:.

By the way, wouldn't a lye discount at the beginning of the process accomplish the same thing ? It also leaves extra oil in the soap.

I thought that the reason behind the standard soapmaking practice of adding superfat oil after the HP cook is to allow one to choose the oil that one doesn't want saponified, so that one can get properties one wants in the resulting soap. Say one wants say a moisturizing bar, one superfats olive oil. If one wants a cleansing bar, one superfats coconut oil. If one wants a hard bar, one superfats lard. and so on.

I'm glad I asked this question because for my next soap batch, I was planning on doing a 4% lye discount (for lye safety) AND a 3-5% superfat (to add moisturizing and lather properties).
 
Superfatting with coconut oil won't make a bar more cleansing. Coconut oil on its own is actually very moisturizing! It's only the when it gets turned into soap that it becomes cleansing. The cleansing/hardness/conditioning numbers aren't affected by which oil is superfat.

Your original plan would have given you a 7-9% superfat in total. Lye discounts and additional superfats stack with one another. And while the idea is that adding a specific oil at the end of a HP cook will give you that oil's properties, there's no actual evidence that it's so, only anecdotal evidence from personal use (that could be biased by the placebo effect).
 
I thought that the reason behind the standard soapmaking practice of adding superfat oil after the HP cook is to allow one to choose the oil that one doesn't want saponified, so that one can get properties one wants in the resulting soap. Say one wants say a moisturizing bar, one superfats olive oil. If one wants a cleansing bar, one superfats coconut oil. If one wants a hard bar, one superfats lard. and so on.

The oils added after the HP cook do not get saponified (presuming no unreacted lye), and thus those properties attributed to them when they become soap (hardness, cleansing etc) do not apply. The super fats remain as fats or oils, unchanged bye the lye reaction. When I superfat after HP I choose oils I prefer for my skin: hemp, sweet almond oil, Shea butter... The more expensive luxury oils that feel good when I rub them on my skin.

I'll happily rub hemp or almond oil on my skin straight from the bottle, not so much olive or sunflower oil.
 
Last edited:
The oils added after the HP cook do not get saponified (presuming no unreacted lye), and thus those properties attributed to them when they become soap (hardness, cleansing etc) do not apply. The super fats remain as fats or oils, unchanged bye the lye reaction.

Yeah, this.

My understanding is that in some ways it's false to atrribute the properties of hardness or cleansing or whatever to the oil itself instead those properties belong to the saponified result. I.E. if you were talking about the properties of coconut oil you should more properly talk about the properties of Sodium Cocoate, which is what the oil becomes once saponified.
 
"...the properties of the soap (like moisturizing, hardness, lather, cleansing, etc.) isn't going to change appreciably when one adds a superfatting oil at the end of the HP cook..."

I don't see where I said something from which you could draw that conclusion. :think:

If one superfats after the HP cook, the unsaponified fat in the soap is mostly or all that specific fat. If you superfat by using a lye discount, whether HP or CP, the unsaponified fat in the soap is a blend of the fats you originally put in the soap pot. Regardless, the unsaponified fat is still going to affect the soap's properties -- lathering, cleansing, hardness, etc.) I don't agree that soap is a moisturizing product.

Like the others have said, don't confuse the properties of the FAT with the properties of a SOAP made from that fat.

And don't confuse the benefits of a fat used in a leave-on product (lotion, salve, balm, etc.) with the benefits of the same fat when used in a wash-off product (soap).
 
Last edited:
Superfatting with coconut oil won't make a bar more cleansing. Coconut oil on its own is actually very moisturizing! It's only the when it gets turned into soap that it becomes cleansing.

The oils added after the HP cook do not get saponified (presuming no unreacted lye), and thus those properties attributed to them when they become soap (hardness, cleansing etc) do not apply.

Oils that add lather such as coconut or castor, have to go through the saponification process, otherwise they are just a conditioning oil.

Is there an oil list that contains the properties of the unsaponified oil AND the properties of the saponified salt of the oil ? Most of the lists out there describe just the properties of the saponified salt of that oil.

Since the soap's properties pretty much come from the saponified salts of the oil, I guess I will stick to the lye discount, and forget about superfatting for now.

I'm glad I talked to you all. I was under a big misconception.
 
Here are two alternate hypotheses that many other soapmakers, including me, subscribe to -- Superfat reduces the cleaning ability of the soap so it doesn't have the negative effect of stripping the skin of its natural oils. And superfat ensures there is no excess alkali in the soap after saponification is complete.

If I read your post correctly, the hypothesis is that the properties of the soap (like moisturizing, hardness, lather, cleansing, etc.) isn't going to change appreciably when one adds a superfatting oil at the end of the HP cook :Kitten Love:.

"...the properties of the soap (like moisturizing, hardness, lather, cleansing, etc.) isn't going to change appreciably when one adds a superfatting oil at the end of the HP cook..."

I don't see where I said something from which you could draw that conclusion. :think:

I made that conclusion because the two alternative hypotheses that you presented implied that the primary function of the oil was to ensure no excess alkali and less harshness, as opposed to the popular hypothesis that superfat oils add properties to the soap.
 
You asked about the benefits of superfat. I replied:

Superfat reduces the cleaning ability of the soap so it doesn't have the negative effect of stripping the skin of its natural oils.

Superfat ensures there is no excess alkali in the soap after saponification is complete.

Your response was that "...the properties of the soap (like moisturizing, hardness, lather, cleansing, etc.) isn't going to change appreciably..."

Soap doesn't moisturize; it cleans.

The disadvantages of superfat is the soap is not as hard and makes less lather.

I already said the benefit of superfat is the cleaning ability of the soap will be reduced.
 
Interesting discussion.

As far as moisturizing properties of left-over oils go, the only plausible mechanism is that there may be a preference created by the fact that some oils are more readily absorbed by the skin than others. Readily absorbable non-saponified oils in the bar may be absorbed by the skin at the same time that less readily absorbable oils are removed. But in any case, especially with expensive and novelty oils, the percentage of the free oils absorbed would have to be a tiny fraction of what goes down the drain.

If you are going to maximize the chances that your expensive or novelty oil will be free in the bar, you would have to:

  1. Make the entire batch out of the novelty oil, which does not seem at all cost effective, and, may not make good soap if the fatty salt of the saponified oil doesn't have useful characteristics, too,
  2. Add the superfat oil after hot process, or
  3. Add it during remill after cold process is done

Usually I go with option 3 because, even though it is very time consuming, it gives me precise control of the outcome and it seems to work better with fragile essential oils I'm adding at the same time(*). Once my processing pipeline is filled, the length of time is no real issue: the loaf I put up today may not be useful for 8 weeks, but the batch I made 8 weeks ago will be useful tomorrow. The turn-around for custom requests can be a bit much, however.

The upshot of all of this is I use a small superfat to protect the end user from any chance of leftover alkali in soaps that I intend to be used as first-run and use zero superfat in anything I am going to re-mill because I will add a small amount of oil during remill. That leads to some inconsistency in re-milling first-run soap scraps, but I live with it.

(*) The absolute best solution for heat-sensitive EOs I have found is putting it on a cloth under the fully cured loaf and leaving it there for several days (all in a sealed container). It appears that the EOs will completely permeate the loaf. I have not had a lot of opportunities to play with that technique yet, however.
 
When I superfat after HP I choose oils I prefer for my skin: hemp, sweet almond oil, Shea butter... The more expensive luxury oils that feel good when I rub them on my skin.

I'll happily rub hemp or almond oil on my skin straight from the bottle, not so much olive or sunflower oil.

So it sounds like the criteria for selecting the oil to superfat with is "whatever feels good on the skin" or "whatever absorbs quickly into the skin". It's not really about adding properties to the soap.

It sounds like if one wants to add properties to the soap, one has to make sure (s)he is saponifying the right combination of oils.

Did I get this right ?

If yes, is there a list of oils that are widely accepted as feeling good on the skin ?

Thanks
 
Last edited:
Yes. If you want soap to have certain properties, focus on formulating the oils that get saponified.

As for what feels good on the skin... That depends on the person. Butters (shea, cocoa, mango seed, etc.), lighter ones like sweet almond or jojoba... A lot of the more expensive oils, really.
 

Latest posts

Back
Top