So, what does superfat look like?

[randycoxclemson]

Sorry if this has been covered, but I searched all topics on Superfat and couldn't find this particular question. (Cue person finding 6 identical topics I couldn't see)

I've made about 60 batches of CP soap now, small batches are 3 pounds, large are upwards of 9. My superfat rate can be anywhere from 2 or 3% to 20% (for a couple of 100% or nearly-100% coconut recipes). A co-worker also makes CP soap and we both have the same question: "What does superfat look like?" or, alternatively, "Where does the oil go?"

It's not like I see slimy oil on the surface of soap, whether it's 5%, 10%, or 20% superfat. But that oil supposedly doesn't saponify, so where is it? I do realize that the soap feels different, and surely has a much shorter lifespan, than store bought soap, but I can't say that I see oil slipping away down the shower drain. And from one batch to the next, they look and feel the same (unless it's a really soft-oil heavy soap that takes a long time to cure, and even then once it's hardened, it looks and feels no different than the coconut at 20% SF bars).

So why don't different soaps with different SF values look or feel different?

 

[dixiedragon]

I would say that different soaps with different superfast do feel different. As to where does the oil go - that's any interesting question. It's still in the soap, obviously. But I do find it an interesting question that we don't see an oil slick with say a 20% superfat. I guess because a 100% coconut oil bar is so cleansing that it cleans up the superfat?

 

[MorpheusPA]

They do feel a bit different, in that my 0% super fat kitchen soap is of a very different texture than my 3% super fat bath soap. And so on; I usually don't go much higher than 5% SF.

Chemically? Spit-balling here, I'd say that since soap is great at forming a micelle around fats in water, it's probably binding down the oils themselves in the soap the same way. Until the amount of fat gets so great that the soap can't hold it, at which point I should think the whole bar starts to fall apart.

High SF soap wouldn't strip your skin so badly because some of the soap is already busy binding the SF, leaving less to strip off your skin.

Of course, gentle, low-SF soap works simply by not being that great a cleaner.

Most of us split the difference; I prefer a modest cleaner with a low-ish SF of 3%.

But check with DeeAnna; she would know better and, if she disagrees with me, it's because I'm completely wrong.

 

[DeeAnna]

What Morpheus said is spot on. The fat is trapped inside the solid crystalline structure of solid soap and/or is buried in the middle of micelles. Micelles are the structures formed by soap when it is dissolved in water. Micelles create an oil-in-water emulsion with soap acting as the emulsifier -- a watery lotion, in other words.

If you've ever handwashed a really greasy batch of dishes, the greasy scum that eventually floats on the dish water is the result when the soap (or synthetic detergent) is overloaded with fat and can't emulsify any more. This can be deadly to plumbing, as Carolyn (cmzaha) knows all too well, according to the stories she's told.

You can also see this emulsification failure if you build in too much superfat into a liquid soap (soap made with KOH rather than NaOH). The fat will separate out of the diluted soap and float on top.