WOemulsjon

WOemulsjon, or water-in-oil (W/O) emulsion, is a type of emulsion in which water droplets are dispersed in a continuous oil phase. In this system, the dispersed aqueous droplets are stabilized by lipophilic emulsifiers that favor interaction with oil, typically with low hydrophilic-lipophilic balance (HLB) values. The oil phase serves as the continuous medium, while the water forms the dispersed phase.

W/O emulsions are usually thick and have an occlusive, grease-like texture. They tend to be more resistant to coalescence under certain conditions than oil-in-water systems, which can give them good stability in the right formulation. Because of their oil-continuous nature, these emulsions are commonly used when a high level of skin occlusion and a long-lasting barrier are desired. They are prevalent in cosmetic bases such as cold creams and ointments, as well as in some pharmaceutical topical formulations.

Formulation and stability rely on selecting suitable emulsifiers with low HLB values and often combining other stabilizers or thickening agents. Preparation requires adequate energy input, such as high-shear mixing or homogenization, and careful control of temperature to maintain the integrity of the oil and water phases. Phase inversion, changes in water content, or shifts in emulsifier balance can convert a W/O emulsion into an oil-in-water system, which is typically undesirable for the original formulation.

Advantages of WOemulsjon include strong occlusion, excellent barrier properties, and suitability for delivering heat- or moisture-retentive topical products. Disadvantages include a heavier, greasier feel and potentially less spreadable texture compared with O/W emulsions.