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Are you also interested in producing cosmetic products consisting of emulsions? In that case, you cannot do without an emulsifier. In cosmetics, an emulsion is most often formed when making creams, body lotions, balms and ointments, that is, products that contain both water and oil.
Oil and water components are mutually immiscible under normal conditions. To create one “compact mass” from them, emulsifiers are used. These are substances that ensure a reduction of surface tension and the dispersion of droplets of one phase into the other. You can achieve the same simply by mixing, but you have certainly noticed that the aqueous and oil phase almost immediately separate again. The role of emulsifiers is therefore also to slow down the time needed for the two phases to separate again, thereby obtaining a stable emulsion. This happens because each emulsifier molecule contains two parts – one that binds to water and the other that binds to oil. With the correct choice of emulsifier for your cosmetic product, you will thus achieve a stable and lasting emulsion.
Knowing the type of your emulsion is important for selecting the right emulsifier. We distinguish the following emulsions:
• O/W – oil in water, where the oil is dispersed in water. An example is body milk or a light face cream. The disadvantage is that due to the higher water content these emulsions are more easily attacked by microorganisms, but at the same time the water causes a cooling effect on the skin. For these emulsions it is suitable to use O/W emulsifiers, which are mostly characterised by providing good spreadability of the product and being stable even below 0 °C. These include for example natural emulsifiers such as Cetearyl alcohol, stearic acid, Glyceryl Stearate Citrate, Sucrose Stearate, Montanov, Olivem, Beautyderm, PolyAquol-2W, Xyliance, Plantasens HE20 and others.
• W/O – water in oil, where conversely water is dispersed in oil. Examples are thicker ointments, balms, night creams and the like. Such emulsions are more demanding to stabilise than O/W and the substances in them must be dispersed into very small droplets. Due to the high oil content they form a greasier film on the skin, on the other hand they are more resistant to microbes and water. This type of emulsion requires W/O emulsifiers, whose advantage is that they are gentle to the skin.
Among this type of natural emulsifiers belong for example Glyceryl Stearate SE, lecithin, Polyglyceryl oleate, Glyceryl oleate, Neocare P3R, Polyglyceryl-4-oleate.
Emulsifiers can also be divided according to their ionic character. The vast majority of natural emulsifiers are non-ionic. There are also anionic exceptions such as Sodium Lauroyl Lactylate. Cationic natural emulsifiers are very rare; their function is fulfilled for example by quats such as BTMS, which however are not classified as natural emulsifiers.
pH of the environment
Most emulsifiers work well in the range of pH 4.5 – 6, this is also the most common pH of cosmetics. If you want to work with products outside these pH values, choose an emulsifier that will work also in this range.
Amount of oil in the product
The proportion of oil and fats in the composition of the emulsion can also influence the choice of emulsifier. Some emulsifiers work better at a lower oil content (5-15 %) in the product, while others are suited to a higher proportion (25-45 %), or intermediate values.
Viscosity of the product
The function of emulsifiers also depends on the viscosity of the product. If you want to make very liquid emulsions for spray dispensers, it is appropriate to choose emulsifiers designed for this purpose, likewise in the opposite case. At the same time, you can partially influence the viscosity (how thick your product will be) also with the emulsifier, by changing the ratio of the oil phase to the emulsifier, which can thicken the product. A similar effect is achieved by adding thickeners suitable for the given emulsifier or by changing the ratio of the aqueous and oil phase in the product.
Character of the oil phase
Not all substances that are part of the oil phase will behave the same when using a given emulsifier. Some emulsifiers work better with paraffins and silicone oils (these are not substances approved for natural cosmetics), others with triacylglycerols (common vegetable oils).
Emulsifiers for cold and hot processes
Most emulsifiers on the market are intended for use in the production of cosmetics by hot process. The hot process consists in heating the aqueous and oil phase of the emulsion to a temperature given either by the stability point of one of the raw materials or by a suitable temperature for the emulsifier, and subsequently mixing these two phases. During cooling it is necessary to stir the mixture, most often with a mixer, to improve the dispersion of droplets of one phase into the other and to form a stable emulsion. There are also emulsifiers for cold processes, which do not require heating to a higher temperature in order to melt and be mixed. This is suitable if you want to save energy for heating the phases, but it also facilitates working with heat-sensitive ingredients.
Influence on colour and scent of the product
Some emulsifiers can influence the colour or scent of the product. If you want snow-white creams, avoid using emulsifiers with a too strong yellow colouring.
Concentration of the emulsifier
In the description of individual emulsifiers you will usually find information directly from the manufacturer on what percentage of emulsifier is appropriate to use in the given product. Some emulsifiers are already a mixture of various substances and so they only need to be used in a smaller amount. Others, on the other hand, must be used in a higher concentration.
Compatibility with other ingredients
When choosing a suitable emulsifier, also consider the other ingredients in the formulation. Some substances destabilise emulsions and it is therefore necessary to use co-emulsifiers. Other components reduce the viscosity, which is compensated for with stabilisers.
Stabilisers and co-emulsifiers
Sometimes it is not enough to use the emulsifier alone, and the formulation requires the use of a co-emulsifier that increases emulsifying capacity, for example fatty alcohols or esters. Alternatively, the product requires stabilisers that contribute to greater emulsion stability.
Texture of the final product
Emulsifiers also have an influence on the texture of cosmetic preparations. This is influenced by a great many factors, so it is not possible to reliably say in advance how a specific emulsifier will react in combination with other raw materials in the recipe, and it is usually necessary to verify this in practice.
Olivem 1000
This is a natural O/W emulsifier suitable for a wide range of pH 3-12, it is added to the oil phase at 75 °C. Its properties are improved by adding 0.2 % of xanthan gum. It can also be used together with co-emulsifiers such as cetyl and cetearyl alcohol to thicken the product. INCI: Cetearyl Olivate & Sorbitan Olivate. It is suitable for making creams and thicker types of emulsions.
Neocare P3R
This is a natural W/O emulsifier suitable for creating very low-viscosity (liquid) emulsions. It is suitable for hot and cold manufacturing processes, and it dissolves in the oil phase. However, it requires stabilisation with electrolytes – MgSO4, NaCl and others. INCI: Polyglyceryl-3 Polyricinoleate, Polyglyceryl-3 Ricinoleate
Beautyderm K10
An alternative to the more expensive Olivem 1000 is Beautyderm. It is a natural O/W emulsifier, soluble in the oil phase at 70 °C, pH range of use 2.5-7. INCI: Sorbitan Olivate, Cetearyl Glucoside, Cetearyl Alcohol. You will appreciate it when making creams or body milks, but also other products.
Lecithin
Another representative from the ranks of natural non-ionic emulsifiers W/O is lecithin. For cosmetic use it is most often obtained from soya or sunflower and is soluble in the oil phase. Lecithin enables the formation of an emulsion, but it does not thicken the product, therefore it is necessary to combine it with co-emulsifiers such as cetyl or cetearyl alcohol, or with the thickener xanthan gum. The advantage is that it is gentle to the skin and moisturises it, and it is used in low concentrations up to 5 %.
There are quite a few factors that are good to take into account when choosing an emulsifier, but this is precisely where there is room for your creativity. In general, the more ingredients your product contains, the more demanding it can be to choose a suitable emulsifier, but it is not impossible. It only requires a bit of experimenting and over time you will find out for yourself which emulsifier suits you best.
