Which type of color penetrates the cortex of the hair?

Permanent color is designed to penetrate the cortex of the hair, which is the thickest layer of the hair shaft. This type of color contains small molecules that can enter the cuticle, which is the outer layer of the hair, and reach the cortex, where it can interact with the natural pigment and alter the hair's color.

The ability to penetrate the cortex is essential for achieving a longer-lasting change in hair color, as permanent colors typically involve a chemical process that lifts the natural color while depositing the new shade within the hair structure. This depth of penetration allows permanent colors to provide rich, vibrant hues that are less likely to wash out compared to other types of hair color.

In contrast, semi-permanent and temporary colors generally do not penetrate the cortex deeply. Instead, they primarily coat the outer cuticle layer, leading to more superficial coloring effects that may fade more quickly. Wash-out colors are similar in nature, offering temporary results that do not involve deep penetration into the hair structure. Understanding these differences is crucial for selecting the appropriate type of hair color based on the desired outcome and longevity.