A liquid foundation is a skin-colored, oil-in-water cosmetic emulsion, usually formulated with inorganic or organic colorants, which is applied to the face to create an even, uniform complexion. Sometimes used to cover flaws or blemishes, or to alter the appearance of the skin’s natural tone, face painting (or body painting when foundation is applied to non-facial areas) and the use of cosmetics to enhance the facial appearance has been known and practised for millennia: the ancient Greeks, Romans and Egyptians, both male and female, would use white lead powder or chalk to lighten their skin.
Homogenizing Color Pigments
Mineral-based (inorganic) colorants are not absorbed by the skin and are rarely water-soluble. Many of them are, however, available in oil dispersions. Organic colorants are mostly synthetic compounds comprising carbon combined with hydrogen, nitrogen and/or oxygen atoms. Color selection depends on the properties of the product formulation and whether they can be dispersed in water or in oil.
High pressure homogenization is a fundamentally important process concerning the use of color pigments in emulsions because it enables efficient particle dispersion to create a suspension with much longer separation times than traditional mixtures.
For optimum performance, homogenizers should operate at pressures of 1000–1500 bar in a single-stage process, and incorporate 3–5 product passes according to the level of required size reduction and ingredient hardness.