How to Choose an Emulsifier (Without Losing Your Mind)
Shake a bottle of salad dressing and watch it separate within minutes. That's oil and water doing what they do best: refusing to mix. Every cream and lotion you've ever loved exists because of one ingredient that settles the argument: the emulsifier.
What an emulsifier actually does
An emulsifier molecule has two ends: one that loves water and one that loves oil. It sits at the boundary between tiny droplets and keeps them evenly spread out instead of merging. Think of it as a diplomat holding hands with both sides.
O/W or W/O? Know your emulsion type
- Oil-in-water (O/W): oil droplets floating in water. Lighter, non-greasy and easy to wash off. Most lotions and face creams.
- Water-in-oil (W/O): water droplets in oil. Richer, more protective and water-resistant. Think barrier balms, cold creams and some foundations.
HLB in plain English
Back in 1949, chemist William Griffin introduced the HLB (hydrophile-lipophile balance) scale to classify emulsifiers by how water-loving or oil-loving they are (Griffin, Journal of the Society of Cosmetic Chemists, 1949). Low numbers lean oil-loving and suit W/O emulsions. High numbers lean water-loving and suit O/W emulsions, with a midpoint around 10 (Griffin, p. 8).
HLB is a great starting point, especially for classic emulsifier pairs. Many modern "complete" emulsifiers (the ones sold ready to use) are designed so you don't need to calculate HLB at all. Just follow the supplier's use range.
A practical chooser
For a classic O/W face cream or lotion:
- Cetearyl Olivate and Sorbitan Olivate: olive-derived, PEG-free and skin-friendly, with a lovely silky feel. Usually 20–25% of your oil phase (see the dictionary entry).
- Cetearyl Glucoside and Cetearyl Alcohol: a sugar-based emulsifier. Natural-origin glucoside emulsifiers have been shown to form stable, non-irritating cream bases that improve skin hydration (Tenside Surfactants Detergents, 2014).
- Glyceryl Stearate Citrate or Polyglyceryl-3 Methylglucose Distearate: gentle, natural-leaning options for light lotions.
- Potassium Cetyl Phosphate: a strong, skin-lipid-like helper that's popular in sunscreens and high-oil creams.
For a rich W/O balm-cream: Polyglyceryl-2 Dipolyhydroxystearate is a PEG-free W/O favourite.
For a cold-process or sprayable lotion: Sucrose Stearate or Lecithin can work with gentle heat, and pre-neutralised polymers can help stabilise.
For hair conditioners: Behentrimonium Methosulfate is both emulsifier and conditioner.
Don't forget the supporting cast
- Co-emulsifiers and thickeners like Cetyl Alcohol and Cetearyl Alcohol add body and stability.
- Water-phase thickeners such as Xanthan Gum help keep droplets apart.
- Oil-phase percentage matters. 15–25% oil is an easy starting point for a lotion. Go higher only with an emulsifier that can handle it.
Five signs your emulsion is unhappy
- It separates, with a watery or oily layer.
- It's grainy (often unmelted fatty alcohols or wax).
- It thins out dramatically over a few days.
- It "soaps" (turns white and foamy) when rubbed in.
- It changes texture after a warm spell or a cold night.
Most fixes come down to the same few things: heat both phases fully (our heat phase guide), mix with enough shear, use enough emulsifier for your oil load, and test stability before you scale up. More on that on Thursday.
Browse the full range in Emulsifiers and Thickeners & Rheology Modifiers.