Solubilizers in cosmetics or how to mix oil with water

In the process of preparing natural handmade cosmetics, we often face the problem of mixing fat-soluble components in an aqueous medium. So, when making a tonic, you want to add essential oil, vitamin E or CO2 extract to the recipe, which are lipophilic substances by their nature. And here solubilizers will come to your aid.

The process of solubilization or solubility

As you already understood, solubilization (from late Latin solubilis - soluble) is the process of mixing hydrophilic and hydrophobic components, which results in a homogeneous substance. We will not go into clever formulations from a course in colloid chemistry, but will simply give practical advice on how exactly you can mix oil and water without using an emulsifier.

How to mix fat-soluble and water-soluble components

For this, you will need special components that can act as solvents. Thus, the most famous solvent for essential oils is alcohol. However, the introduction of alcohol into natural cosmetics formulations contradicts many principles of hand-made products, and so they went on to search further. The next most popular oil solubilizer after alcohol are non-ionic surfactants Polysorbate-80 and Polysorbate-20. They are capable of dissolving essential oils in a 1:1 ratio. You can also dissolve difficult-to-dissolve powders in polysorbates, such as salicylic acid.

Water-soluble oils (WSO) can be an excellent replacement for polysorbates. They themselves dissolve perfectly in water, and with the correct ratio of WSO to lipophilic components, you will get an opaque aqueous solution, which should be added to the remaining aqueous part of the cosmetic recipe with active stirring. As a result, you will get a homogeneous aqueous product, but it cannot be called crystal clear. And the more fat-soluble components and WSO you use, the less transparent the finished product will be.

A more well-known oil solvent is PEG-40 or hydrogenated castor oil. For high-quality dissolution of fragrances and essential oils, it is recommended to maintain a ratio of 1:4 without additional heating. But when introducing denser oil components into the recipe, it is better to increase the proportion of PEG-40 and take a ratio of 1 part oil to 5-8 parts solubilizer (1:5 - 1:8). In this case, it is advisable to heat the hydrogenated castor oil to a temperature of about 70 C, then add the oil, mix thoroughly and then add water.

Organic cosmetic solubilizers

Keeping pace with the rapidly developing cosmetic industry, natural plant solvents for lipophilic components have begun to appear on the market. We would like to introduce you to Pentylene glycol - a multifunctional active that acts as a solubilizer and additionally plays the role of a moisturizing and antimicrobial agent, enhancer and emulsion stabilizer. The component is approved by ECOCERT/COSMOS. To dissolve fatty components, the manufacturer recommends maintaining a 1:1 ratio, but from personal experience, it is better to increase the amount of pentylene glycol to avoid undissolved lipophilic actives floating on the surface of the water after mixing the two phases. Depending on the substance you are dissolving, the ratio can be 1:3 or even 1:5 if these are difficult-to-dissolve dry components or acids. Heating this mixture improves the solubility of the components in each other.

Another interesting representative of solvents is the Italian active Resassol VPF (INCI: Polyglyceryl-4 Caprylate, Sodium Lauroyl Glutamate, Water, Decyl Glucoside, Diglycerin, Potassium Hydroxide), based on a system of soft surfactants and does not have an irritating effect on the skin. It is approved for use in leave-in cosmetics and is approved by COSMOS. The main advantage of Resassol VPF over many solvents is that in most cases it does not require heating, and the ratio of oil to solvent is significantly lower than, say, PEG-40.

Another interesting natural ingredient is Tegosoft 41 MB, which is a hydrophilic emollient, co-surfactant and solubilizer for natural cosmetics. Tegosoft 41 MB is a surfactant based on polyglycerol. It does not contain PEG and has exceptional dissolving properties, especially for light polar emollients, while not irritating the skin. Tegosoft 41 MB is one of the most popular ingredients on the cosmetic market, which allows you to create transparent micellar water without introducing surfactants into the recipe. The component is not tested on animals, does not contain nanoparticles and is able to increase foaming in recipes.

We present you with a comparative table of the solubility of various components in two solvents, the data in which was provided by the manufacturer of the solubilizer, Res Pharma.

Watch a video on how and in what to dissolve oils for introduction into the aqueous phase and what the result will be on our youtube channel Beurre Cosmetic Kitchen