Bulking

Ingredients with the bulking function are used primarily to change the physical properties of the formula: they help to make the product more dense, voluminous and visually "filled". In decorative cosmetics and dry textures, such substances improve the feeling of velvety texture, facilitate distribution over the skin and can make the coating more even and soft-matte. For skin and hair, this is usually not an active care effect, but rather an effect on the fit and comfort of the product: the powder lies more smoothly, the foundation seems silkier, and hair products can give a feeling of a thicker texture. The European CosIng database classifies bulking as an officially used cosmetic function, and the data from the industry directory INCI/PCPC confirm the use of such substances precisely as components that form the volume and mass of the product. (single-market-economy.ec.europa.eu)

Typical examples are Nylon—12 and Zinc Oxide. For nylon polymers, including Nylon-12, Cosmetics Info specifies the bulking agent function; in addition, such powders are valued for their easy gliding and ability to improve the sensory of makeup. Zinc oxide is also described as a bulking agent and a white powder that can simultaneously act as a pigment, so in formulas it affects not only the density, but also the appearance of the product. In practice, such ingredients are especially common in powders, foundation, primers, eye shadow, and some care products where a stable texture, pleasant application, and a more "complete" feeling of the formula are important without necessarily having a therapeutic effect on the skin or hair. (cosmeticsinfo.org)