PSI Barbering Practice Exam 2026 - Free Barbering Practice Questions and Study Guide

A surfactant is a substance that reduces the surface tension of a liquid, which is essential in various applications, including cosmetology and sanitation. Surfactants accomplish this by disrupting the cohesive forces between liquid molecules, allowing them to spread more easily across surfaces. In the context of barbering and beauty products, surfactants are commonly found in shampoos, conditioners, and cleansers, where they help to improve wetting properties, enabling better cleaning and foaming action.

The other options, while related to the formulation and stabilization of products, serve different functions. An emulsifier is primarily used to mix two immiscible liquids, such as oil and water, preventing them from separating. A stabilizer helps maintain the integrity of a formulation, ensuring that the components remain blended and do not settle. A thickener is used to increase the viscosity of a product, giving it a more substantial texture without necessarily impacting surface tension. Thus, while all these substances play critical roles in product formulation, it is the surfactant that specifically targets and decreases surface tension.