Colorado Cosmetology Written Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

Ammonia is the correct answer because it is a strong alkaline substance that raises the pH of hair products. Increasing the pH levels in these formulations allows for the opening of the hair cuticle, facilitating better penetration of the product into the hair shaft. When the hair cuticle is lifted, it enables further treatment or conditioning agents to reach and affect the inner layers of the hair, leading to more effective results in processes such as coloring or deep conditioning.

The other options do not serve this purpose. Glycerin is primarily a humectant that helps in retaining moisture rather than altering pH. Peroxide is commonly used as a bleaching agent, but it does not specifically function to raise pH for the purpose of penetration. Silicon dioxide, on the other hand, is primarily used for its thickening properties and does not interact with pH in a way that facilitates hair shaft penetration. Thus, ammonia stands out as the key ingredient for raising pH in hair care formulations.