PEG-100 Stearate

Overview

PEG-100 Stearate is a polyethylene glycol ester of stearic acid with approximately 100 moles of ethylene oxide. That long hydrophilic chain gives it an exceptionally high HLB of about 18.8 — one of the highest you will find among common cosmetic emulsifiers. The result is a strongly water-loving molecule that excels at creating lightweight, easily absorbed O/W emulsions.

It arrives as a white to off-white waxy solid that melts around 50-55 C. Because of the extensive ethoxylation, it is extremely effective at dispersing small amounts of oil into a water phase, producing lotions that feel thin, fresh, and non-greasy on the skin.

PEG-100 Stearate is one of the most widely used emulsifiers in commercial cosmetics. If you have ever picked up a drugstore moisturizer and noticed how light it feels, there is a reasonable chance PEG-100 Stearate is on the ingredient list. It is PEG-based, which makes it incompatible with strict “PEG-free” formulation guidelines.

What it does in a formula

PEG-100 Stearate pulls oil into water extremely efficiently, creating very fine oil droplets that result in a non-greasy, fast-absorbing lotion. It does not build much viscosity on its own, so it is almost always paired with glyceryl stearate as a co-emulsifier. That combination is so common it is practically an industry standard — glyceryl stearate adds body and stabilizes the emulsion structure while PEG-100 Stearate handles the heavy lifting of dispersion.

The finished texture is characteristically light. If your goal is a thick, butter-like cream, this is probably not your emulsifier — its natural tendency is toward fluid, silky lotions.

How to use

Melt PEG-100 Stearate into your oil phase at 70-75 C alongside glyceryl stearate and your chosen oils. Heat the water phase to the same temperature, then combine with stick-blending or high-shear mixing.

Typical usage rates:

• Light facial moisturizers: 1-2% PEG-100 Stearate + 2-4% glyceryl stearate
• Body lotions: 2-3% PEG-100 Stearate + 3-5% glyceryl stearate
• Lightweight hand creams: 1.5-2.5% PEG-100 Stearate + 3-4% glyceryl stearate

Keep the oil phase modest (10-20% total) for the lightest texture. This emulsifier can handle higher oil loads, but it is at its best in lean formulas. If your oil phase exceeds 25%, consider a different emulsifier or increase the co-emulsifier to compensate.

Best for / Worst for

Best for: lightweight day creams, facial moisturizers for oily or combination skin, body lotions that should absorb quickly, formulas where a non-greasy finish is the priority, SPF products that need a lightweight feel.

Worst for: rich night creams or body butters (too lightweight), W/O emulsions (HLB far too high), PEG-free product lines, anhydrous formulations, products that need a thick and luxurious texture.

Common pitfalls

Skipping the glyceryl stearate. PEG-100 Stearate alone produces a thin, unstable emulsion. It genuinely needs the co-emulsifier. Some suppliers sell them pre-blended — if yours is a blend, check the data sheet before adding extra glyceryl stearate.

Overloading the oil phase. This emulsifier is designed for lean formulas. Pushing the oil phase above 25-30% without increasing your emulsifier system will result in separation.

Using it for rich textures. If your target is a dense, buttery cream, PEG-100 Stearate will fight you. Switch to a lower-HLB system like Steareth-21/Steareth-2 or Ceteareth-20 with cetearyl alcohol.

Confusing the pre-blended version with the pure ingredient. Some suppliers sell “glyceryl stearate and PEG-100 stearate” as a single product. If you have that blend, you do not need to add more glyceryl stearate. Read your supplier’s data sheet carefully.

Substitutes

• Ceteareth-20 — lower HLB (~15.5), produces a slightly richer texture, also PEG-based.
• Polysorbate 60 — high HLB (~14.9), similar lightweight finish, also needs a co-emulsifier.
• Olivem 1000 — PEG-free self-emulsifying system, heavier texture, olive-derived.
• Glyceryl Stearate Citrate — PEG-free O/W emulsifier, produces a light cream with a modern “clean” claim.