The duration for which purple-pigmented shampoo should remain in contact with hair varies depending on factors such as the hair’s porosity, the desired level of toning, and the shampoo’s formulation. Typically, the recommended time ranges from one to fifteen minutes. Over-application, meaning excessively long contact time, can result in an undesirable lavender or grey tint, especially in highly porous or light blonde hair.
Correct application time is crucial for neutralizing brassy or yellow tones in blonde, bleached, or highlighted hair. This neutralization process helps to maintain the vibrancy and intended color of the hair, preventing it from appearing dull or discolored. Historically, methods to correct unwanted yellowing in hair have evolved from less refined techniques to the current use of specifically formulated shampoos with purple pigments.