Friday, February 5, 2010

E-mail question: Why include stearic acid?

Here's an e-mail from Marie: Can I just say that your blog is simply brilliant!! I am from the UK and love crafting my own stuff . May I ask you a question? Why stearic acid in lotions / creams? If reducing water can make a thicker cream, and using a heavier oil can do the same, as well as butters, why do we need to add stearic acid? I’ve always added a little extra cocoa butter or shea butter (this has a high level of stearic acid doesn’t it). And we’ve already got an emulsifier…So why stearic?

Okay, now I'm blushing...but let's get on with the answer! There are a few reasons for using stearic acid. (And I think this applies to cetyl alcohol as well!)

1. It's a thickener. Although you can reduce the water or increase the butters to get thickness, stearic acid is a quick and easy way to add the thickness. And you need less stearic acid to thicken than you would do butters. 3% stearic acid can thicken better than say 10% butters.

2. It's inexpensive. Butters might be $20 a pound, whereas stearic is rarely over $5, and usually less. So adding 3% stearic acid is cheaper than adding 10% butter.

3. It has a long shelf life. Yep, most butters do, too, but we know our creation will have at least a two year shelf life using stearic acid.

4. It gives body to the recipe. For instance, I found a beautiful recipe on the Dish for a whipped body mousse. It has very simple ingredients - oil, emulsifier, water, preservative, and stearic acid. Without the stearic acid, we would have a very light lotion. But stearic creates a thickened, mousse-y quality to the lotion that we wouldn't get otherwise. A butter would weigh it down, so stearic is the best choice.

5. It's also an emollient - stearic acid is a great softener - and to get 3% into a recipe using butters you'd have to use at least 10% shea, cocoa, or mango butter. You can use it in a lotion and call it "oil free" because it's not an oil, it's a fatty acid.

Having said this, you can most certainly leave out stearic acid and just go with more butters or a reduction of water if you like. Try a little experiment - try your favourite lotion recipe with stearic and another version without. It's easy to see what the stearic brings to the mix: It offers a stiffening you don't see with the butters. The butters add emolliency and stiffening, but add a little greasiness; stearic acid adds emolliency and thickening without the greasiness.

14 comments:

Susan said...

That is a great explanation. I've always wonder what percentage of butter the acid would replace.

Lalla said...

Thanks for the explanation.

I was wondering about that myself and made a few batches of lotion to test the effect of stearic acid and cetyl alcohol compared to shea butter and cocoa butter.

Do waxes (olive wax, beeswax, jojoba wax...) have the same effect?

Li said...

Thanks! I've been wondering about this myself.

Susan Barclay-Nichols said...

Hi Lalla! Waxes will thicken your lotion and form an occlusive layer, but at a certain point they will thicken far too much and feel waxy and annoying on your skin. (I use 2.5% beeswax in one of my hand lotions so it will withstand washing and water!) I wouldn't go over 2.5% beeswax in a recipe - for the other, harder waxes, like carnauba or candellia, you'll want to use less.

Aditi said...

Interesting......I was searching for an answer to reduce oilyness in my creams. Do we first dissolve steari acid in water and then mix it with oil ?

Susan Barclay-Nichols said...

Hi Aditi! Check out my answer to your comment in this post Saturday, February 9th or later. The short answer is that stearic acid doesn't reduce greasiness.

Louise said...

I hate the idea of anything "unnatural" in a skin or face cream. I also don't like greasiness, but my skin is sensitive and I'd prefer an airy, light cream, like mousse. Wouldn't high speed whipping provide volume or density while allowing a light application and less greasiness? That's what I'm looking for.

Susan Barclay-Nichols said...

Stearic acid. isn't unnatural! It's in our bodies, in all our butters, in our food! If you want only natural ingredients, then you might want to make anhydrous products, and you can whip butters easily because of all the stearic and palmitic acids!

Monique said...

Hi,

You stated we could 10% less butter by replacing it with stearic acid? Can you give us an example for a formula? I am worried about my whipped shea butter melting during the summer months. If I were to replace a portion of the shea butter for the stearic acid, what percentage would you suggest? Also, would this resolve the melting butter issues as well?

SquarePancake said...

I know this is an older post, but could you use stearic acid in water-free mixes? I've done salves before, but I'd like to reduce the wax.

Anonymous said...

Thanks, i was doing a school project on products you use daily this was in my product and i had to explain what it was!😀

m. said...
This comment has been removed by the author.
The Soap Mistress said...

Question??? I've found a recipe I"d like to try it's a shaving soap recipe and it calls for soy wax which is made up of 85% steriac acid. My question is I don't have soy wax can I just sub the soy was for steriac acid in the soap and if so would it be an even swap or would I need to adjust the amount? thank you.

Susan Barclay-Nichols said...

Hi Soap Mistress. I recommend you write to the person who wrote the recipe and ask if this substitution would work. Soy wax is not a substitute for stearic acid and vice versa.