Zoya Formulates

What Does an Emulsifier Do?

An emulsifier is an ingredient that helps keep oil and water from separating.

Many emulsifiers are amphiphilic(a fancy word for saying it has two different properties at once), more specifficaly meaning they have two different parts:

A hydrophilic head, which likes water
A lipophilic tail, which likes oil

The water-loving head interacts with the water phase, while the oil-loving tail interacts with oils, sebum, and grease. This allows the emulsifier to sit between the oil and water and help stabilize the droplets.

In simple terms, the emulsifier acts like a bridge between two ingredients that normally do not get along.

Surface Tension and Interfacial Tension

To understand emulsions more deeply, it helps to know the idea of interfacial tension.Oil and water resist mixing because there is tension at the boundary where they meet. Emulsifiers help redduce this tension, making it easier for one phase to break into tiny droplets and stay dispersed in the other phase.The smaller and more stable the droplets are, the more uniform and elegant the product can feel.

Why Emulsions Feel Different

Not all emulsions feel the same. A lotion, cream, and body butter may all be emulsions, but they can feel completely different depending on the formula.

A lightweight lotion may contain more water and lighter emollients. A rich cream may contain more oils, butters, waxes, fatty alcohols, or occlusive ingredients. This completely changes the texture profile and overall feel of the product which is critical for a well received skin product 

The feel of an emulsion depends on things like:

This is why two moisturizers can have similar ingredients but feel totally different on the skin.

Emulsion Instability

A good emulsion should stay smooth and uniform over time. However, emulsions can become unstable if they are not formulated properly.

• The oil phase
• The water phase
• The emulsifier system
• The droplet size
• The viscosity
• The thickeners and stabilizers
• The humectants, emollients, and occlusives used

Some common types of instability include:

Creaming: This is where droplets move upward or downward, creating uneven layers.

Flocculation: This is when droplets cluster together but do not fully merge.

Coalescence: This occurs when droplets merge into larger droplets.

Phase separation: Best described as when the oil and water phases fully separate.

When a product separates, changes texture, or becomes grainy, it may be a sign that the emulsion is unstable.

Why Emulsification Matters in Skincare

Emulsification is what allows a product to combine water-based ingredients with oil-based ingredients in one formula.

This is paramount because skin often benefits from both. Water-soluble ingredients, like glycerin or hyaluronic acid, can help with hydration. Oil-soluble ingredients, like certain emollients or lipids, can help soften the skin and support the barrier.