What chemical process is responsible for changing hair color during coloring treatments?

The chemical process responsible for changing hair color during coloring treatments is oxidation. In the context of hair coloring, oxidation occurs when the coloring agent, typically an oxidizing agent like hydrogen peroxide, interacts with the hair's natural pigments. This reaction lifts the existing color and allows the new dye to penetrate the hair shaft.

During oxidation, the melanin (natural pigment in hair) is broken down, which can lighten the hair color. Depending on the formulation of the dye and the method used, oxidation helps create a new hair color by allowing dye molecules to form larger, more permanent color molecules in the hair.

This process is essential because it not only alters the hair's existing color but also ensures that the new color adheres to the hair effectively, resulting in vibrant and long-lasting color results. Other processes listed, such as hydration and condensation, do not play a role in permanent hair coloring; fermentation is also unrelated to the chemical changes associated with hair dyeing.