Which chemical technique involves applying a lightener and then a color?

The technique that involves applying a lightener and then a color is known as a double process. This method is used to achieve a desired hair color that is significantly lighter than the natural shade, particularly for dramatic color changes.

In a double process technique, the first step involves using a lightening agent to lift the hair's existing pigment. After the hair has reached the desired level of lightness, the second step is the application of a toner or color to achieve the final hue. This process allows for more control over the final color, ensuring that the new shade is vibrant and accurately reflects the desired outcome.

This technique is particularly useful for those looking to achieve pastel shades or unconventional colors that cannot be obtained directly on darker hair without prior lightening.