Polyhydroxystearic acid vs stearic acid is a solids-handling question, not a spelling variant. Polyhydroxystearic Acid is the yellow liquid polymer used to wet pigments and mineral filters. Stearic Acid is octadecanoic acid, a white wax used to thicken oil-in-water creams and to build sticks. Sharing the word “stearic” does not make the drums interchangeable.
If the brief has not locked the dispersant’s CAS and the slurry step, start with Polyhydroxystearic Acid Dispersant for Mineral Filters. If the brief is a comedogenic chart that scored “stearic,” that chart is Polyhydroxystearic Acid Comedogenic Rating: Not an Oil.
What each page is selling
| Polyhydroxystearic Acid | Stearic Acid | |
|---|---|---|
| INCI | Polyhydroxystearic Acid | Stearic Acid |
| CAS | 27924-99-8 (58128-22-6 is the other registry number on the INCI) | 57-11-4 |
| What it is | Polymer of hydroxystearic acid; non-surfactant dispersing agent | C18 fatty acid, typically a triple-pressed cosmetic grade at 98% or higher |
| Form on this site | Yellow liquid | White waxy flakes, beads, or powder |
| Where it goes | Oil phase. Mix with pigments or mineral filters first, then the rest of the oil | Oil phase. Heat to about 75°C until the solids are clear, then emulsify |
| Listed use | 1–5% as dispersant and W/O co-emulsifier | 1–5% where the page talks about barrier-style creams; 10–20% for sticks or cleansing balms |
| Water | Not a water-phase charge | Insoluble in water; soluble in hot oils, esters, and alcohols |
| Melt | Liquid at ambient temperature on this page | Melting point listed at 67–72°C |
A grind that needs a dispersant and receives stearic flakes will not wet the pigment the same way. A stick that needs stearic acid and receives the yellow polymer will not set on the melt point of the fatty acid. Quote the row that matches the chassis.
The monomer is a third material
CIR defines Polyhydroxystearic Acid as the polymer made from hydroxystearic acid. The monomer has its own identity. Hydroxystearic acid is not Stearic Acid, and it is not the finished polymer. This site has no page for hydroxystearic acid. Do not invent a URL, and do not ship either of the two pages above when the document says only “12-hydroxystearic acid.”
A molecular-weight note in the CIR file belongs to a named polymer grade, not to stearic acid. Stearic acid on this site is listed at 284.48 g/mol. That single-molecule weight is not the polymer’s number-average or weight-average mass. If a COA prints 284 and the INCI line says Polyhydroxystearic Acid, the lot is the wrong substance.
How to choose on a real brief
Choose the polymer liquid when the problem is viscosity of a pigment or mineral-filter grind, or when a W/O cream needs this co-emulsifier in the oil. The dispersant page is explicit: slurry the solids with the liquid before the remaining oils. The percent to write first is 1–5%, then the TDS.
Choose the fatty acid when the problem is body in an oil-in-water cream, opacity, or a solid stick. The stearic page tells you to melt it in the oil at about 75°C. Its higher band, 10–20%, is for sticks and cleansing balms, not for wetting titanium dioxide.
Titanium Dioxide still has to be purchased as titanium dioxide. The polymer helps disperse it. Stearic acid does not become the white pigment because both can sit in a color cosmetic.
Polyglyceryl-2 Dipolyhydroxystearate and PEG-30 Dipolyhydroxystearate stay out of this swap as well. They are emulsifiers that contain polyhydroxystearate chains. They are not stearic acid, and they are not this homopolymer. Name them only when the formula already names them.
What to send for the material you need
For the dispersant:
- INCI Polyhydroxystearic Acid
- CAS 27924-99-8
- Yellow liquid, oil-phase slurry, starting window 1–5%
- The pigment or filter INCI on its own line
- COA, SDS, TDS, and bench-sample size
For the fatty acid, use the other product page:
- INCI Stearic Acid, CAS 57-11-4
- White flakes or beads, assay 98% or higher if that is your spec
- Whether the chassis is a cream at 1–5% or a stick at the higher band
- Oil-phase melt, not a water charge
- COA, SDS, TDS, and bench-sample size
Dispersant documents are on the Polyhydroxystearic Acid product page. Stearic documents are on the Stearic Acid product page. Match the sample to the column you specified, then scale. A purchase line that says “stearic for the dispersion” will be read as the flake unless you write the polymer INCI.
