Ask ten formulators for the backbone of a classic oil-in-water cream and most will say "glyceryl stearate". It is the most-used nonionic emulsifier in personal care — cheap, vegetable-derived, multifunctional (emulsifier, opacifier, consistency factor, emollient). But "glyceryl stearate" on a spec sheet is not one product: the INCI name covers three chemically different materials with different CAS numbers, different HLB positions and very different formulation behaviour. Buying the wrong one is the most common reason a new cream lot is thin, gritty or pH-unstable. This guide separates the three — Glyceryl Stearate (CAS 31566-31-1), Glyceryl Stearate SE (CAS 11099-07-3) and Glyceryl Stearate Citrate (CAS 39175-72-9) — and walks through selection, use levels and the COA specs that matter.
One INCI family, three different chemistries
- Glyceryl Stearate (GMS, CAS 31566-31-1) — glycerol monostearate, the neutral monoester of glycerin and stearic acid. INCI Glyceryl Stearate. HLB ~3.8, oil-soluble, non-self-emulsifying. It is a co-emulsifier and consistency factor: on its own it stabilizes W/O systems and thickens the oil phase, but it cannot carry an O/W emulsion alone.
- Glyceryl Stearate SE (CAS 11099-07-3) — GMS blended or reacted with a small amount of alkali soap (potassium/sodium stearate), the "SE" standing for self-emulsifying. INCI Glyceryl Stearate SE. HLB ~5.5–6.5. The trace soap converts it into a genuine primary emulsifier for O/W lotions and creams — provided the pH stays alkaline (see below).
- Glyceryl Stearate Citrate (GSC, CAS 39175-72-9) — the mixed ester of glycerin with stearic and citric acid. INCI Glyceryl Stearate Citrate. HLB ~10–12 depending on the citrate content. A true O/W primary emulsifier that works across the acidic-to-neutral range and is prized for lamellar gel networks and elegant skin feel in face care.
The practical trap: a supplier's "glyceryl stearate" quote may be any of the three. Always specify the INCI name and the CAS number on the PO — the CAS is the only unambiguous identifier, because a technical GMS drum and a self-emulsifying drum differ by a few percent of soap and behave nothing alike at the bench.
Selection by formulation role
| Material | HLB | Typical use | Role in the formula |
|---|---|---|---|
| Glyceryl Stearate (31566-31-1) | ~3.8 | 1–5% in the oil phase | Co-emulsifier, opacifier, viscosity/consistency builder for creams; W/O stabilizer; pearl effect partner in anhydrous and emulsion systems |
| Glyceryl Stearate SE (11099-07-3) | ~5.5–6.5 | 2–5% as primary emulsifier | Carries O/W lotions and creams alone or paired with cetearyl alcohol; the classic "cold-cream" workhorse since the 1950s |
| Glyceryl Stearate Citrate (39175-72-9) | ~10–12 | 2–4% as primary emulsifier | O/W primary emulsifier with lamellar gel-network formation; excellent skin feel, stable in acidic (pH 4.5–7) face care; pairs with glyceryl stearate for dense, cushiony creams |
The pH question — where SE emulsions break
Glyceryl Stearate SE owes its self-emulsifying power to a small amount of ionized fatty-acid soap. That soap is only effective while it stays ionized: keep the finished formula above roughly pH 7 (typical working range 7–9). Drop the pH below 6–6.5 and the soap protonates back to neutral stearic acid, the interfacial film collapses, and the emulsion visibly separates within weeks — often after passing the initial stability check. Two consequences in practice: first, SE is the wrong choice for acidic formats (AHA/BHA treatments, pH 4.5–5.5 "skin-neutral" claims) — choose GSC or a PEG-based system there. Second, the alkaline pH that keeps SE stable is itself a formulation constraint: niacinamide, some peptides and several preservatives dislike pH 8+, so check the whole formula, not just the emulsion.
Glyceryl Stearate Citrate has no such cliff. The citrate head group is anionic but not soap-based, so GSC systems hold from about pH 4.5 to 7, tolerate common electrolytes far better, and are the default choice for facial creams positioned around "pH-balanced" or mild-acid claims.
How the classic pairings work
GMS + PEG-100 Stearate (3:1). The most successful emulsifier couple ever commercialized. Glyceryl stearate sits in the oil phase; its PEGylated partner sits at the interface; together they form a mixed interfacial film plus a lamellar gel network with fatty alcohols that gives creams their body and snow-white opacity without heavy wax loads. Typical total loading 3–5% at roughly 3:1 GMS:PEG-100 stearate, with 2–6% cetearyl alcohol as the gel-network co-structure. Cetearyl alcohol (and) PEG-20 stearate is the ready-made blend version of this logic when you want one raw material instead of two.
SE + cetearyl alcohol. Glyceryl Stearate SE at 3–5% with 3–8% cetearyl alcohol builds the traditional stearate cream: thick, white, soap-stable, low cost. The cetearyl alcohol is not optional — without the co-structure the SE emulsion is a thin lotion at best.
GSC + GMS. In premium face care, 2% GSC plus 1–2% plain GMS gives a dense, cushiony gel-network cream with a low-PEG or PEG-free label. GSC also contributes genuine emolliency and reduces the greasiness that high wax levels cause.
Preservative-boosting cousins worth knowing
Two other glyceryl esters in the same family earn their place by supporting preservation rather than emulsification. Glyceryl Caprylate (CAS 26402-26-6) at 0.2–0.5% boosts the efficacy of the preservative system (particularly against bacteria) while adding a distinct emollient feel; Glyceryl Undecylenate (CAS 123759-97-7) at 0.3–1% is the standard booster for yeast and mould control in "preservative-light" or natural-positioned formulas. Both are PEG-free and pair naturally with GSC-based, mild-label emulsions.
COA specs that separate a good drum from a bad one
- Monoglyceride content — the single most important number for GMS. Technical grade runs 40–60% monoester (the balance is di- and triglyceride); high-purity grades reach ≥90%. Higher mono content means sharper melting, better opacification and more reproducible emulsions. For SE and GSC, ask for the degree of esterification or the citrate value instead.
- Acid value — free fatty acid. Cosmetic-grade GMS should be ≤ 5 mg KOH/g (good lots ≤ 2). A rising acid value means hydrolysis, and hydrolyzed lots smell of rancid fat and destabilize emulsions.
- Melting point / dropping point — GMS melts around 55–63 °C depending on mono content; a lot melting low is short of monoester or contaminated with liquid esters. Also your process check: the oil phase must be fully melted (≥ 75 °C) before emulsification or the cream will grain.
- Iodine value — measures unsaturation (hydrogenated grades < 2–4 g I₂/100 g). High iodine value predicts yellowing and rancidity on shelf.
- Saponification value, hydroxyl value, color (Gardner/APHA) — routine identity checks; color drift signals aging oil feedstock.
- Heavy metals and glycidol risk — for food-contact or premium cosmetic use, request glycidyl ester data; esterified glycerol lipids can carry trace glycidol if processed hot, and premium buyers increasingly screen for it.
Sampling and procurement practice
The procurement workflow that avoids the classic glyceryl stearate traps: specify INCI + CAS on the PO (31566-31-1 / 11099-07-3 / 39175-72-9 are not interchangeable), reject COAs that do not report monoester content and acid value, and pilot the actual pH journey of your formula — for SE systems, run accelerated stability at the final pH and at pH −0.5, because the soap cliff appears there first. Vegetable (palm/KO) and tallow-derived GMS are chemically equivalent but differ in religious/certification positioning, so state the origin requirement explicitly.
Shanghai Better Chemical supplies the full glyceryl ester family — Glyceryl Stearate (CAS 31566-31-1), Glyceryl Stearate SE (CAS 11099-07-3), Glyceryl Stearate Citrate (CAS 39175-72-9), as well as Glyceryl Caprylate and Glyceryl Undecylenate for preservative boosting — with per-lot COA, monoester/acid-value data, RSPO-certifiable palm origin on request, and TDS/MSDS support. Tell us your emulsion type, target pH and label positioning, and we will recommend the right grade and quote current pricing.