In the cosmetic industry, emulsions are wildly used. They are composed of two immiscible liquid phases: water and oil phase. One is the dispersed phase and another is the continuous phase. The dispersed phase exists in the form of microparticles, dispersed within the continuous phase. The primary objective in formulating emulsions is to achieve stabilization, as emulsions tend to separate over time. This is where emulsifiers play a crucial role, by binding the phases together and maintaining them in the emulsified state. Emulsifiers can be surfactants or a combination of surfactants (1).
The choice between an oil-in-water (O/W) or water-in-oil (W/O) emulsion determines the sensory experience and is primarily influenced by the intended purpose of the cosmetic product (1).
O/W emulsions provide a non-sticky, lightweight, and moisturizing sensation. They can be utilized in both rinse-off and leave-on cosmetics.
W/O emulsions impart an oily sensation and are employed in rinse-off and leave-on products that require specific performance characteristics, such as certain cleansing creams and cream foundations (1).
This emulsion is a basic example of O/W emulsion, designed to explain the utilized ingredients and their respective functions within the cosmetic formulation.
1. Upon the completion of research and development of the cosmetic formula, as well as the acquisition of the necessary ingredients, we are now prepared to proceed with the formulation of the facial cream (Figure 1.)
Figure 1. The steps of creating an emulsion.
2. Ensure proper sanitization of the required equipment.
For this cosmetic formula we will need:
2 glass beakers
Spoons, droppers, whisk
Precision balance
Water bath
Homogenizer
Cosmetic jars
3. Switch on the water bath.
4. WATER PHASE:
Accurately measure the components of the water phase and introduce them into the container. Take note of the precise weight of both the water phase and the container together (Table 1.).
Distilled water | Skin protectant, skin conditioning agent- humectant, and viscosity-decreasing agent (2) |
Chelating agent, formulation stabilizer, prevent discoloration, enhance the activity of preservatives (3) | |
Sodium Phytate | Chelating agent, formulation stabilizer, prevent discoloration, enhance the activity of preservatives (3) |
Phenoxyethanol (and) Methylparaben (and) Butylparaben (and) Ethylparaben (and) Propylparaben | Strong broad spectrum effective preservative (4) |
Table 1. Ingredients of the water phase and their purpose in the emulsion formulation.
5. OIL PHASE:
Accurately measure the components of the oil phase and introduce them into another container (Table 2.).
Emollient, high content of linoleic acid, repairs the skin barrier (5) | |
C12-15 Alkyl Benzoate | Dry emollient ester, broad spectrum solvent, increases slip and reduces drag properties of an emulsion (6) |
Cetyl Alcohol | Non-ionic emulsifier, compatible with other emulsifiers, thickening agent (7) |
Glyceryl Stearate (and) PEG 100 Stearate | Non-ionic emulsifier, compatible with high levels of electrolytes, compatible with other emulsifiers (8) |
Xanthan Gum | Natural thickener, suspending agent, stabilizer, provides excellent rheology or texture control (9) |
Table 2. Ingredients of the oil phase and their purpose in the emulsion formulation.
6. Place both phases in the water bath and heat them until the oil phase dissolves completely, ensuring that both phases reach the same temperature.
This typically takes around 20 minutes, aiming for approximately 75 degrees Celsius.
7. After the heating process, pour the warm distilled water into the water phase container until it reaches the same weight it had before heating.
8. Now, it is time for the emulsification stage.
Gradually pour one of the phases into the other using a whisk. Then mix with a homogenizer for a period of 2 to 5 minutes.
9. COOL-DOWN PHASE:
Once the lotion has cooled down to 45°C, incorporate the cool-down phase ingredients and thoroughly mix them into the lotion (Table 3.).
Geranium oil | Fragrance* |
Table 3. Ingredient of the cool-down phase and its purpose in the emulsion formulation.
* Before selecting a fragrance, it is essential to verify the permissible concentration levels in accordance with the IFRA (International Fragrance Association) standards.
10. Transfer the cream into jars only when it has completely cooled down to room temperature. This precaution is necessary to avoid condensation formation inside the container. It’s important to note that the condensation does not contain any preservatives.
11. Typically, it takes approximately one day for the cream to fully thicken and achieve the desired texture. Allow this time for the cream to set properly.
Enjoy the final result!
References:
1. H. Iwata, K. Shimada. Formulas, Ingredients and Production of Cosmetics. 1st edition. Springer Japan 2013
2. Becker LC, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler DC, et al. Safety Assessment of Glycerin as Used in Cosmetics. Int J Toxicol. 2019 Nov;38(3_suppl):6S-22S.
3. MMP Europe. Phytate MM Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
4. DKSH. Euxyl® K 340 Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
5. Lin TK, Zhong L, Santiago J. Anti-Inflammatory and Skin Barrier Repair Effects of Topical Application of Some Plant Oils. IJMS. 2017 Dec 27;19(1):70.
6. Phoenix Chemical, Inc. PELEMOL® 256 Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
7. Kao Chemicals Europe, S.L. KALCOL® 6098 Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
8. Inolex. Lexemul® 561 MB Datasheet Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
9. Unionchem, Xanthan Gum CT Datasheet [Internet]. UL Prospector. [cited 20 May 2023].
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