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 and shea.
INCI Stearic Acid
Appearance Small white beads or pellets; it’s easy to confuse with other white pellets like emulsifying wax.
Usage rate 1–25% (lower amounts are typically for emulsions, higher amounts are typically for anhydrous products)
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. Small amounts (1–4%) in lotions will significantly thicken them. When used in products like cleansing balms or emulsified sugar scrubs stearic acid thickens without the weight and waxiness of waxes.

I also 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 without any added wax.
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 It is a bit of a niche ingredient.
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.

I don’t recommend using a true wax as an alternative for stearic aid. Faux 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 it in your heated oil phase; it needs to be melted into products.
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!
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