Virginia Cosmetology Practice Exam

The primary ingredient in hair bleach is hydrogen peroxide. This compound acts as an oxidizing agent, which is essential for the lightening process of hair. When applied to the hair, hydrogen peroxide penetrates the hair shaft and breaks down the natural melanin, the pigment responsible for the hair's color. This chemical reaction is what leads to the lightening effect observed when using hair bleach.

Hydrogen peroxide is typically found in various concentrations in hair bleaches, allowing for different levels of lightening depending on the desired result. Its effectiveness and relatively quick action make it a staple ingredient in most hair bleach formulations.

The other options serve different purposes: sodium hydroxide is often used in chemical relaxers due to its ability to break down protein structures in hair; ammonia helps to open the hair cuticle for better penetration of other products, like hydrogen peroxide; and calcium carbonate is primarily used as a buffering agent or filler, but it does not play a role in the bleaching process itself. Thus, hydrogen peroxide stands out as the key component that enables the hair lightening process in bleaching products.