What is the difference between a single process and a double process hair color?

The distinction between a single process and a double process hair color primarily lies in the steps involved in achieving the desired hair color. A single process refers to one application of color that can either lighten or darken the hair in a single step, typically achieving the desired tone in one go. This is often used for all-over color or to cover gray hairs.

In contrast, a double process involves two distinct steps: first, a bleaching application is performed to lighten the natural hair color, followed by an application of toner or color to achieve the desired shade. This method allows for more dramatic changes, particularly moving from dark to light shades, and is often used for achieving pastel or vibrant colors that require an underlying light base.

While there are other considerations regarding application time and the techniques used, the fundamental difference centers on the required steps to reach the final color result, which is accurately captured in the explanation of the processes.