What technique requires two separate procedures involving pre-lightening the hair before color application?

The technique that requires two separate procedures involving pre-lightening the hair before applying color is known as a double process. This method is commonly used when transitioning hair to a significantly lighter color or to achieve a vibrant hue that cannot be accomplished in a single application due to the depth of the original color.

During the first step of a double process, the hair is lightened to achieve the desired level of brightness, and then a second color application is applied to deposit the new shade. This two-step approach allows for a more accurate and even color application, especially on darker hair, ensuring that the final results are vivid and true to the desired color. It is an essential technique for achieving results in fashion colors, light blondes, or when correcting color mistakes, as simply applying color over darker hair without lightening first would not yield the desired results.