Stearic/Palmitic acid "film"

[kelleyaynn]

I tried my first lard soap this morning, and while the bar is nice and hard, and the lather was really creamy, it left my skin feeling like there was a film on it, much like commercial soap. The same thing happened when I tried my cream shaving soap. I figured the hardness of the lard bar was due to stearic acid, and cream soap is made with a lot of stearic acid, so I wondered if that had anything to do with it. After a bit of research, I found out that lard has a relatively high amount of stearic acid, and even more palmitic acid, which is very similar chemically. They both harden the bar and contribute to a stable lather. I read that minerals in hard water can react with stearic acid (and so I assume also with palmitic), creating insoluble salts that leave a film on the skin (and ring around the tub). My water isn't really hard, but it is far from soft, so I'm guessing this is what is happening here. Interestingly, I checked the ingredients of several commercial soaps this past weekend, and many of them are made with beef tallow, which has a large percentage of stearic acid.

So my question is, has anyone else found soap made with a large percentage of lard to leave a film on the skin?

 

[agriffin]

I wonder if it's more of a superfat thing. How much did you superfat?

 

[kelleyaynn]

I don't have my recipe here, but I think it was 7 - 8%.

 

[carebear]

I don't think it's only those two fatty acids that are problematic. It's just that hard water + soap (sodium salts of fatty acids) = soap scum. On skin, as well as on the shower walls. Just ask the folks who make Dove, and Zest for that matter. That is one way in which detergent bars are superior - detergents don't do the same thing.

Using a chelating agent such as tetrasodium EDTA or citric acid can mitigate this.

I regularly superfat at 15% and it's not an issue in my water.

 

[kelleyaynn]

I don't think it's only those two fatty acids that are problematic. It's just that hard water + soap (sodium salts of fatty acids) = soap scum. On skin, as well as on the shower walls. Just ask the folks who make Dove, and Zest for that matter. That is one way in which detergent bars are superior - detergents don't do the same thing.

Using a chelating agent such as tetrasodium EDTA or citric acid can mitigate this.

I regularly superfat at 15% and it's not an issue in my water.

But my other soaps don't have the same "film on m skin" feel.

 

[carebear]

I dunno, then.

 

[cthylla]

Using a chelating agent such as tetrasodium EDTA or citric acid can mitigate this.

I regularly superfat at 15% and it's not an issue in my water.

If you don't mind my asking, how much citric acid PPO do you add? I have EXTREMELY hard water here.

 

[carebear]

I've never worked with the citric acid.
Sorry.

 

[gekko62]

I know what you mean about the cream soap.It's sort of a waxy draggy feeling? Have never experienced that with bar soap tho.

 

[kelleyaynn]

I know what you mean about the cream soap.It's sort of a waxy draggy feeling? Have never experienced that with bar soap tho.

It's the same soap film feeling I get using commercial bar soap. My other handcrafted soaps don't leave the same soap scum feeling.

 

[Jerry S]

Lard soap

In the past I have made a lot of soap with lard and I as well, find that most of the time soap that is made with lard has a tendency to leave some residue both on myself and the walls of the shower if I chose to use it that way.

Most of the lard soap I make is used as hand soap and so I wasn’t bothered to much about the residue. Lard soap cleans so well that there is no substitute for it for auto mechanics getting their hands clean (most use rubber gloves now) and from doing chores around the farm. When I was a young boy doing chores I would complain to my Mom that I couldn’t get my hands clean. She would say “either use some bacon grease or use the lard soap in the wash room”…lol. It worked…but…we seldom used it in the tub or shower.

I think that Carebear has a point when she says, “I don't think it's only those two fatty acids that are problematic. It's just that hard water + soap (sodium salts of fatty acids) = soap scum, on skin, as well as on the shower walls,” but I think the high fatty acids do contribute to the residue.

Jerry S