What does the term "double processing" refer to in hair coloring?

The term "double processing" in hair coloring specifically refers to the technique of applying both bleach and toner to achieve the desired hair color. This process typically involves first lightening the hair with bleach to a very light blonde or a pale base. After achieving the desired level of lift, a toner is then applied to adjust the tone, neutralize unwanted brassiness, or enhance the overall color effect. This two-step process is essential for creating high-lift colors and achieving professional-looking results, especially when aiming for fashion colors or icy blondes that require precision in tone.

The other options do not accurately capture what double processing entails. Using two different brands of dye is not a recognized technique that defines double processing; rather, it focuses on the specific actions taken during the coloring procedure. Mixing hair color with a developer is a standard step in many coloring processes, but it does not involve the dual action of bleaching followed by toning. Applying color twice for deeper saturation might enhance the vibrancy of the color, but it does not incorporate the necessary lightening phase that defines double processing.