Glyceryl Monostearate (GMS)

Overview

Glyceryl monostearate — universally called GMS in formulation shorthand — is a waxy, white solid made by esterifying glycerin with stearic acid. It’s one of the oldest and most common cosmetic ingredients in existence, found in nearly every white lotion and cream on the market. That pearlescent, opaque white colour you associate with moisturizers? That’s largely GMS at work.

GMS has an HLB value of around 3.8, making it a lipophilic (oil-loving) emulsifier. On its own, it’s too weak to hold a proper oil-in-water emulsion together — it needs a partner. Paired with a stronger primary emulsifier (something with an HLB of 12-16), GMS co-emulsifies, thickens, and opacifies the formula into that classic lotion texture.

There are two grades to be aware of: “GMS pure” (glyceryl stearate alone, INCI: Glyceryl Stearate) and “GMS SE” (self-emulsifying, INCI: Glyceryl Stearate SE), which is pre-blended with a small amount of sodium or potassium stearate to make it a complete emulsifier on its own. This entry covers the pure (non-SE) version — the co-emulsifier.

What it does in a formula

GMS plays several roles simultaneously:

1. Co-emulsifier — stabilizes oil-in-water emulsions when paired with a primary emulsifier. It sits at the oil-water interface and reinforces the emulsifier film, preventing separation.
2. Opacifier — creates the white, pearlescent appearance of lotions. Even a small amount transforms a translucent emulsion into a creamy white product.
3. Thickener — adds body and viscosity to the oil phase, contributing to lotion thickness without heaviness.
4. Emollient — the stearic acid portion conditions skin, leaving a smooth, non-greasy after-feel.
5. Consistency factor — contributes to the “slip and glide” of a lotion during application, then absorbs cleanly without tackiness.

In practice, GMS is almost never the star of a formula — it’s the supporting actor that makes everything else work better.

How to use

• In lotions and creams: 2-5% in the oil phase. Melt with other oil-phase ingredients at 70-75 C. Combine with your primary emulsifier (the one that actually holds the emulsion together).
• Common pairings:
  • GMS (2-4%) + Cetearyl Alcohol + Polysorbate 60 (complete system)
  • GMS (2-3%) + a complete emulsifying wax (adds body and whiteness)
  • GMS (3-5%) + Ceteareth-20 (classic cosmetic combination)
• In conditioners: 2-4% alongside cetearyl alcohol and a cationic emulsifier (BTAC). Provides slip and conditioning.
• In body butters: 2-3% to add body and improve skin-feel without waxiness.
• Temperature: Must be melted into the oil phase at 70 C+. Won’t disperse if added cold.
• Cooling: Hold the emulsion at 70 C+ during the emulsification step (oil + water phases combined). Cool slowly with gentle stirring.

Best for / Worst for

Best for: lotions, creams, hair conditioners, body milks, co-emulsification alongside a primary emulsifier, opacifying translucent emulsions, improving skin-feel and slip, cold cream formulas.

Worst for: clear/transparent products (it opacifies everything), gel formulas, anhydrous products where you want transparency, PEG-free or “simple emulsifier” systems where it adds unnecessary complexity, very lightweight spritz-type emulsions.

Common pitfalls

Using alone as a primary emulsifier. Pure GMS (non-SE) has an HLB of ~3.8 — far too low to stabilize an oil-in-water emulsion on its own. Without a high-HLB partner, your lotion will separate within hours or days. Always pair with a complete emulsifier system.

Confusing GMS with GMS-SE. GMS-SE (self-emulsifying) contains added soap and CAN work as a primary emulsifier. Pure GMS cannot. Check your INCI — if it says “Glyceryl Stearate (and) PEG-100 Stearate” or “Glyceryl Stearate SE,” that’s the self-emulsifying version.

Too much = heavy, draggy texture. Above 5%, GMS starts making lotions feel heavy, waxy, and slow to absorb. The sweet spot for most face creams is 2-3%.

Soaping effect at high pH. Above pH 8, the stearic acid in GMS can partially saponify, creating a soapy feel and destabilizing the emulsion. Keep final pH between 4-7 for best stability.

Graininess from uneven cooling. Like any stearic-acid-rich ingredient, GMS can crystallize unevenly if cooled too quickly or without stirring. Cool slowly with consistent gentle mixing below 45 C.

Substitutes

• Glyceryl Stearate SE — self-emulsifying version, can work alone, different INCI.
• Cetearyl Alcohol — similar thickening and co-emulsifying, less opacifying.
• Cetyl Alcohol — lighter co-emulsifier and thickener, no pearlescent effect.
• Stearic Acid — simpler fatty acid, similar thickening, needs TEA or NaOH to emulsify.
• Glyceryl Stearate Citrate — naturally derived alternative with built-in emulsifying power.