What effect does the large size of color molecules in temporary hair color have?

The large size of color molecules in temporary hair color primarily prevents penetration beyond the cuticle layer. This is significant because temporary hair colors are designed to coat the outside of the hair shaft without altering the internal structure of the hair. The cuticle layer, which is the outermost layer, serves as a protective barrier, and since the color molecules are too large to penetrate deeper into the hair, they remain on the surface. This characteristic allows for easy application and removal of temporary color, making it ideal for those who want a non-permanent change. Consequently, because these molecules do not penetrate the hair shaft, the color will wash out after several shampoos.