What is the function of a toner in hair color?

A toner serves the primary function of neutralizing unwanted tones in hair color. This is particularly important after the hair has been lightened or dyed, as the underlying pigments in hair can sometimes result in colors that are not desirable. For example, when someone bleaches their hair, it may take on brassy, yellow, or orange tones. A toner can adjust these tones by adding complementary colors that counteract the brassiness, resulting in a more balanced and aesthetically pleasing hair color.

In contrast, while strengthening hair strands, lightening original hair color, or adding volume can be beneficial aspects of hair care and styling, these actions do not specifically define the role of a toner. A toner does not have a direct impact on the structural integrity of the hair nor does it contribute to physical volume. Its main purpose is to refine the final hue and ensure that the color meets the desired result.