What concept describes the repeated application of hair color to the shaft?

The term that best describes the repeated application of hair color to the hair shaft is build-up. When hair color is applied multiple times, especially if the color contains certain pigments and chemicals, those substances can accumulate on the hair fibers. This build-up can affect the hair's appearance, texture, and even the efficacy of future color applications. It can lead to darker shades if the same or similar colors are used repeatedly, as well as potential issues with hair quality, such as drying out or becoming overly saturated with pigment. Understanding this concept is crucial for hairstylists as managing and removing build-up can help maintain hair health and achieve desired results with color treatments.