Black hair dye is one of the most difficult colors to remove from hair, as it is a large molecule that can easily penetrate the hair shaft. Once black dye has been applied to hair, it can be very difficult to lighten or remove it without causing damage to the hair.
There are a few different ways to remove black dye from hair, but the most effective method is to use a color remover. Color removers are chemical products that work by breaking down the dye molecules in the hair shaft, allowing them to be washed away. However, color removers can be harsh on hair, so it is important to follow the instructions carefully and to use a deep conditioner after using a color remover.