Why are color molecules able to penetrate the cuticle layer of the hair when using semi-permanent products vs temporary colors?

• A. Color molecules are smaller in size
• B. Color molecules are larger in size
• C. They are more alkaline
• D. They have stronger pigments

Answer: (A)

The cuticle is made of overlapping scale-like cells that form a barrier on the hair’s surface. For color to penetrate, the dye molecules have to fit through or between these scales, which is much easier when the molecules are small and the hair is softened or swelled by the product. Semi-permanent formulas use smaller, often water-soluble dye molecules that can diffuse into the cuticle (and sometimes a bit into the cortex), giving longer-lasting color. Temporary colors rely on larger pigment particles or film-forming agents that stay on the surface and don’t penetrate the cuticle. So, smaller color molecules are able to penetrate the cuticle, while larger ones remain on the outside.