What is used to mix substances together in cosmetic formulations?

The correct answer is the emulsifier. Emulsifiers play a vital role in cosmetic formulations because they facilitate the blending of two immiscible substances, such as oil and water. By lowering the surface tension between these substances, emulsifiers stabilize mixtures and help maintain a uniform consistency in products like creams, lotions, and other emulsified formulations. They effectively create a stable mixture that ensures the product's efficacy and texture remain consistent over time.

Binders are primarily used to hold particles together, enhancing the cohesion of the product rather than mixing different substances. Solvents dissolve solid, liquid, or gaseous solutes to form a solution, which is different from the process of mixing distinct phases like oil and water. Thickeners increase the viscosity of a formulation without necessarily stabilizing mixtures, focusing primarily on altering the texture rather than combining different ingredients effectively.