Which technique is essential to achieve a lighter shade when using oxidative color?

To achieve a lighter shade when using oxidative color, the technique of double processing is essential. This method involves two key steps: first, the hair is lightened with a bleach or a high-lift color to remove the natural pigment. After achieving the desired level of lift, the second step involves applying a toner or a second color to deposit the desired shade. This process ensures that the hair reaches a light enough base to apply the final color, resulting in a brighter and more vibrant outcome.

In contrast, the other techniques mentioned serve different purposes. Balayage is a freehand highlighting technique that creates sun-kissed effects, but it may not consistently lighten the hair as effectively as double processing for a uniform lighter shade. Highlighting involves applying lightener to select strands or sections but does not always reach the necessary level of lift needed for a complete color change. Undercoloring typically refers to dyeing the underneath layers of hair a different color, working more for dimensional effects rather than uniformly lightening the hair. Thus, double processing is specifically designed for achieving a significant lightening effect, making it the ideal choice for reaching a lighter shade with oxidative color.