The skin and hair applications we commonly refer to as cosmetics, which include everything from shampoos and soaps to moisturizers and makeup, are products of chemistry. Selecting from more than 5,000 different ingredients, each with its own essential function, cosmetic chemists combine water, oils, color, emulsifiers, preservatives, thickeners, and fragrances in different ways to produce formulations, or mixtures, designed to alter or protect users' appearance or scent.

The process a chemist follows is an orderly description of each task that must be accomplished to make the product. This is akin to a recipe for baking. If the chemist does not follow the directions and use the ingredients in prescribed quantities, the final product may not turn out as planned.

Ingredient selection is a critical step in cosmetic manufacturing because the ingredients determine the properties and effectiveness of the final product. Most cosmetic products are mixtures of two or more liquids (e.g., perfumes), two or more solids (e.g., powders), or a combination of liquids and solids (e.g., lipsticks). Mixing ingredients together does not, by itself, create a new substance or substances, so no chemical change is said to occur. Because the original ingredients retain their chemical properties, they remain present in a mixture and can be separated by physical means, such as distillation, evaporation, or precipitation.

Like perfumes and powders, lipsticks and glosses are simple mixtures. The ingredients used depend on the specific properties they are meant to exhibit, such as shininess, texture, durability, and color. The girls featured in this video tested and evaluated different formulations for many of these properties. People frequently lick their lips, so water solubility is an important factor in creating lip applications. But because dyed, insoluble wax alone would be too hard to apply, the wax is combined with ingredients to produce a substance that is stiff but still spreadable. Most lip applications are mixtures of natural or petroleum-based wax, oily materials, and pigments. Once the ingredients have been determined, they are melted, stirred together, and cast into molds.

While waxes, oils, and pigments are commonly recognized ingredients of most cosmetics, others, such as emulsifiers, might need some explaining. A colloid is a mixture in which particles of one phase (solid, liquid, or gas) are distributed within and throughout another. For example, an emulsion is a type of colloid in which both phases are liquids. Creams and lotions are all emulsions of water and oily materials. Because water and oil do not readily mix, ingredients called emulsifiers are added to make the formulation work. Emulsifiers change the surface tension between two otherwise unmixable materials, thereby preventing their separation. Emulsifiers, then, are what enable a product to be applied to the skin with an even texture.

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