Wisconsin Barber Practice Exam

Temporary hair color has the largest molecules among the hair color categories because its molecules are too large to penetrate the hair shaft and instead sit on top of the hair, creating a coating. Permanent and demi-permanent hair color have smaller molecules that can penetrate the hair shaft and bond to the hair's pigment. Semi-permanent hair color also has smaller molecules, but they only deposit color onto the outer layers of the hair, rather than penetrating the hair shaft.