What is the primary function of a toner in hair coloring?

The primary function of a toner in hair coloring is to remove unwanted brassiness. Toners are typically used after the hair has been lightened or highlighted to correct or adjust the underlying tones that can appear, especially the yellow or orange hues that may emerge in the hair. This is particularly important in achieving a more natural or desired shade, such as cooler blondes or ashy tones.

Using a toner helps to refine the color, making it look more balanced, vibrant, and polished. While toners can also contribute to enhancing shine and may assist in camouflaging gray hair by providing a subtle sheen over the strands, their main purpose is to adjust or neutralize any undesirable warm tones present after the lightening process, which is essential for creating the overall look that clients often seek.