Single-Process Color Vs. Double-Process Color: What's The Difference?

As the name suggests, single-process color — sometimes also referred to as all-over color — is a method of hair coloring that consists of a single application. "Single processes give you an all-over one color with little to no dimension. You may get slight variations of color if you use semi-permanent [hair color]," master colorist Stephanie Brown shared in a conversation with Byrdie, adding that the one-step dyeing technique is "minimally damaging" and great for root touch-ups. Other than all-over hair color, the single-process color method can include highlights that don't need toning as well as hair gloss coloring treatments, as per L'oreal Paris.

The purpose of getting a single-process color, according to colorist Nancy Braun, is "either to lighten the hair, darken the hair ... or change the tone," she explained when talking to Hair.com by L'oreal. The overall process is less time-consuming than your average hair coloring, which consists of multiple steps but may require more upkeep depending on the placement of the hair color.

For example, if you're just doing lowlights that don't require toner, your next maintenance appointment could probably wait for at least a few months. On the other hand, if you went for an all-over color that covers the entire surface of your hair, your roots may start showing fairly quickly. While getting a single shade all-over might make your hair color flat, single-process coloring individual strands can create dimension rather than take it away.