Before any hair dye application, hair should be assessed for which of the following?

Before applying hair dye, it is crucial to assess the color history of the hair. Understanding the previous color applications and treatments the hair has undergone allows the barber or stylist to make informed decisions about the new dye choice and technique. This assessment helps identify any potential challenges, such as color build-up, which can affect how the new dye will show up on the hair, the level of processing required, and the overall health of the hair.

Color history can reveal if the hair has existing dye, which could result in unexpected results if not considered. For instance, hair that has been previously bleached may react differently to color than virgin hair. A thorough understanding of the hair's color lineage will ensure the desired outcome is achieved, reducing the risk of damage or uneven color results.

While other aspects, such as the health of the scalp, presence of natural oils, and hair length and thickness, are also important for overall hair care, they do not directly influence the choice and application of hair dye as significantly as color history does.