A Beginner’s Guide to Cosmetic Emulsifiers

Every stable lotion or cream you’ve ever used relies on an emulsifier — an ingredient whose entire job is to hold oil and water together in a form that doesn’t separate on the shelf. Get the emulsifier wrong and no amount of good ingredients elsewhere in the formula will save it.

What an emulsifier actually does

Emulsifiers are molecules with a water-loving end and an oil-loving end. They sit at the interface between your oil phase and water phase and effectively glue the two together into tiny stable droplets, rather than letting them separate back into layers.

The easiest starting point: Emulsifying Wax NF

Emulsifying Wax NF is where most beginner formulators start, and for good reason — it’s forgiving, widely compatible, and produces a stable oil-in-water emulsion without a steep learning curve. If you’re formulating your first lotion, this is very likely the emulsifier you want.

For hair conditioners specifically: BTMS 85

BTMS 85 is a different category of emulsifier — a conditioning emulsifier purpose-built for hair care. It doesn’t just hold a conditioner together, it actively contributes detangling slip and softness, which is why it’s the standard choice for rich conditioners and hair masks rather than skin lotions.

Solubilisers: a different job entirely

Not every “helps oil and water mix” ingredient is a true emulsifier. Polysorbate 20 and PEG-40 Hydrogenated Castor Oil are solubilisers — they disperse small amounts of oil (like fragrance or essential oils) into a mostly-water formula, such as a toner or room spray, without building a full lotion-style emulsion. Don’t reach for a solubiliser expecting it to emulsify a lotion; it’s built for a much smaller job.

Supporting ingredients: co-emulsifiers

Fatty alcohols like Cetearyl Alcohol aren’t primary emulsifiers on their own, but they’re commonly blended in as co-emulsifiers — they add thickness, stability and a silkier after-feel to an emulsion built around a primary emulsifier like Emulsifying Wax NF.

A simple decision framework

Formulating a lotion or cream? Start with Emulsifying Wax NF. Formulating a hair conditioner? Reach for BTMS 85. Just need to disperse fragrance into a watery spray? Polysorbate 20 is your ingredient, not a full emulsifier.

Choosing between two specific emulsifiers? See Emulsifying Wax NF vs BTMS 85.