Stearic Acid

At a glance

CAS number

57-11-4

INCI name

Stearic Acid

Function

emollient, emulsifier, thickener, surfactant

Typical use level

1%–15%

Solubility

oil

Stable pH

4–8

CAS number and synonyms are sourced from PubChem. Function, usage levels, pH and compatibility are AI-assisted formulation guidance — verify against your supplier's technical data sheet and applicable regulations before use.

Also known as

Octadecanoic Acid C18 Fatty Acid Stearic Acid 50 Triple Pressed Stearic Acid Vegetable Stearic Acid

Compatibility

Works well with:
Glycerin Cetyl Alcohol Triethanolamine Shea Butter Beeswax Dimethicone

Use caution with:
Strong oxidizing agents Strong bases at high concentrations

Stearic acid reacts with alkaline agents such as triethanolamine or sodium hydroxide to form soap (stearate salts), which is a deliberate formulation technique used to build emulsions and creams. At high pH or with excess strong base, full saponification can alter the intended texture and feel of a formula. It is generally stable and compatible with most cosmetic ingredients within typical formulation pH ranges.

Formulation notes

Stearic acid is a saturated long-chain fatty acid widely used to thicken, stabilize, and add a pearlescent or opaque quality to creams, lotions, and cleansers. When neutralized with an alkali, it self-emulsifies and forms the backbone of many classic cold-cream and lotion systems. It is considered safe and well-tolerated, though formulators should source from reputable suppliers to ensure purity, as commercial grades often contain palmitic acid as a co-component.

Frequently asked questions

Related ingredients

• Glyceryl StearateEmulsifier
• Arachidyl AlcoholEmollient
• Behenyl AlcoholEmollient
• Stearyl AlcoholEmollient
• Behenyl PEG/PPG-20/20 DimethiconeEmulsifier
• Cetearyl AlcoholEmulsifier