Stearic Acid

What is it? Stearic acid is an isolated fatty acid we use as a thickener and hardener in lotions, salves, body butters, and more. It occurs naturally in butters like cocoa butter (~36%), shea butter (~38%), and kokum butter (~54%), as well as in some liquid oils like plum oil (~2%) and sunflower oil (~4%).

It is possible to source stearic acid from non-vegan sources, but I have never found non-vegan stearic acid for sale. It’s usually derived from palm, but I have found canola oil derived steric acid as well. Check with your supplier to see which plant oil your stearic acid is derived from.
INCI Stearic Acid
Appearance Small white beads or pellets; it’s easy to confuse with other white pellets like emulsifying wax.
Usage rate For emulsions, generally 1–5%. For anhydrous products, 1–40/50%.

It’s unlikely you’d ever need or want more than 50% in a formulation, but you can try it! Click here to learn more about how different concentrations of stearic acid impact anhydrous formulations.
Texture As part of our products it stiffens/hardens and adds a butter-like creaminess/weight. When melted into liquid oils I find it gives them a more buttery consistency.
Scent Nothing much; perhaps a bit fat-like.
Absorbency Speed Medium to slow
Approximate Melting Point 69.3°C (156.7°F)
Solubility Oil
Why do we use it in formulations? Stearic acid stiffens/hardens our products. The more you use, the harder/thicker your formulations will be!

Small amounts of stearic acid (1–5%) in lotions will significantly thicken them.

When used in anhydrous rinse-off products like cleansing balms or emulsified sugar scrubs, stearic acid thickens while maintaining excellent rinse-off (unlike true waxes, which can leave a tacky film behind).

I like including it in salves, balms, body butters, and body butter bars—with or without wax. With stearic acid you can use less wax, which improves skin feel. You can also use stearic acid to make a blend of liquid oils feel buttery, and in larger amounts, to stiffen/harden without any added wax.

Stearic acid is also very useful for raising the melting point of body butters and other anhydrous formulations—brilliant if you live somewhere hot!
Do you need it? I sure love it and would highly recommend it—it’s inexpensive, versatile, and has a long shelf life. If you can get 100–200g that’ll last you quite a while.
Strengths It’s a strong thickener without the weight and tack of waxes; I find it gives a rich buttery feel to products.
Weaknesses I can’t think of any!
Alternatives & Substitutions Stearic acid is pretty hard to swap out. It is a stronger thickener/hardener than both cetyl alcohol and cetearyl alcohol, so if either of those are used as an alternative the end product will be softer. Stearic acid also produces creamier/richer products, so the end product will feel thinner/less substantial on the skin. Out of the two, cetearyl alcohol is the better option, but you’ll likely need to do a bit of re-formulating.

I don’t recommend using a true wax as an alternative for stearic aid.

Faux/pseudo waxes (“waxes” that are actually hydrogenated vegetable oils—check the INCI!) may be a decent alternative in some situations, but you will have to do some experimentation to determine usage rates and if the end feel still works for you.
How to Work with It Include stearic acid in the heated oil phase; it needs to be melted into products.

Try blending stearic acid with cetyl alcohol for a great creamy, slippy thickening combination!
Storage & Shelf Life Stored somewhere cool, dark, and dry, stearic acid should last at least two years.
Tips, Tricks, and Quirks Stearic acid has a higher melting point than beeswax!

Stearic acid is not acidic and will not lower the pH of your formulations like citric acid or lactic acid.

A 2:1 blend of stearic acid and triethanolamine can be used as an emulsifier (it’s what LUSH uses in most of their lotions!).
Recommended starter amount 100g (3.3oz)
Where to Buy it  Buy it from an online DIY ingredient supplier or Amazon.

Some Formulations that Use Stearic Acid

Skills

Posted on

November 23, 2018