Emulsions

What are emulsions and how do you make them

What is an emulsion?

Emulsions are finely dispersed mixtures of two substances that are not soluble in each other. In cosmetics, these are usually water and oil. On their own, the two cannot be mixed, but emulsifiers make it possible to bring these two substances together and create something new.

Emulsions can be divided into two phases: water phase and oil phase.

The water phase includes not only water and other aqueous components (e.g., aloe vera juice or hydrosols) but also water-soluble active ingredients and additives.

The oil phase includes, for example, oils, waxes, and other oil-soluble substances.

What is an emulsion made of?

An emulsion can contain a multitude of raw materials and active ingredients, as it can contain not only water- and oil-soluble substances but even completely insoluble ones (e.g., mineral substances, exfoliating particles, pigments, etc.).

 

The following substances are commonly found in emulsions:

Water phase

• Water (aloe vera, hydrosols, fruit waters, etc.)
• Humectants/solvents (glycerin, alcohol, glycols, sugar alcohols)
• Water-soluble active ingredients (hyaluronic acid, urea, etc.)
• Gel formers (xanthan gum, starches, synthetic polymers, etc.)

Oil phase

• Lipids (vegetable oils, waxes, cosmetic oils, silicones, etc.)
• Emulsifiers and consistency agents (waxes, fatty alcohols, solid fats)
• Additives
• Preservatives
• Chelating agents (bind metal ions in water)
• Antioxidants (e.g., vitamin E)
• Fragrances/essential oils
• Colorants

The consistency of emulsions

How viscous (consistent) an emulsion is does not necessarily say anything about its effectiveness or its oil content. It is entirely possible to make emulsions with a high water content very highly viscous. Through the right emulsifier and the use of consistency agents and gel formers, you can create very thick creams. Conversely, it is also possible to produce thin emulsions with a high oil content. In general, highly viscous emulsions are referred to as creams, low-viscosity ones as lotions, and thin ones as milks.

Types of emulsions

There are essentially two types of emulsions: oil-in-water emulsions and water-in-oil emulsions. The difference lies in which is the internal and which is the external phase.

Contrary to popular belief, the type of emulsion has nothing to do with the phase proportions, but only with the choice of emulsifier. It determines which type of emulsion is formed – not whether the oil or water content is higher. In almost all emulsion products, the main part is water.

Oil-in-water emulsion (O/W)

In this type of emulsion, the internal phase is the oil phase. This means that small oil droplets are finely dispersed in water. Since the external phase is the water phase, this is what you feel first when applying it. This leads to a cool, fresh feeling during application.

O/W emulsions are the most common on the market because they generally enjoy high customer acceptance.

Water-in-oil emulsion (W/O)

In this type of emulsion, the internal phase is the water phase. Small water droplets are finely enclosed in oil. Since the external phase is the oil phase, this is what you feel during application. Thus, one perceives W/O emulsions as rich or greasy at first. Depending on the product, this may change after a short application time.

How are emulsions made?

To produce an O/W cream, for example, you measure the water phase and the oil phase separately. Both are heated.

The oil phase usually contains waxy components, such as emulsifiers and consistency agents. These must be melted before they can be processed further – this often happens between 70 and 80 degrees Celsius.

After that, the hot phases are poured together and can then be stirred. It is recommended to stir at "high speed," i.e., with a device that can achieve a high number of revolutions (e.g., a hand blender). However, this can vary from recipe to recipe and also depends on the emulsifier used.

Now the emulsion forms – the oil phase is broken up into tiny droplets and finely distributed in the water phase. The emulsifier ensures that it stays that way. Subsequently, it is cooled down slowly while stirring with a spatula. If the emulsion is hot, it is quite thin; this changes as it cools down.

The consistency agents ensure that the cream becomes viscous. However, this can take some time. Often, the final consistency of an emulsion is only reached the next day.