What is the difference between oxidative color (permanent) and direct dye (semi or demi) in terms of chemistry and longevity?

• A. Oxidative color uses peroxide to develop pigments and lift; direct dye uses pre-formed pigments and generally fades faster
• B. Oxidative color uses direct pigments and fades quickly
• C. Direct dye colors hair by oxidizing pigments with peroxide to lift
• D. Direct dye requires heat activation

Answer: (D)

Pigment formation and how it’s held in the hair differentiate oxidative color from direct dye. In oxidative color, a developer such as hydrogen peroxide activates dye precursors, which then oxidize and join to form new pigment molecules. These newly formed molecules are small enough to penetrate the cortex and, as they form, become trapped inside the hair fiber, giving color that lasts until the hair grows out or is recolored. In direct dye, the pigments are already formed when applied; they deposit on the surface or near the cuticle and are held mainly by physical adhesion rather than bonding to the cortex. Because there isn’t a chemical bond inside the hair, these pigments gradually wash out or fade with washing, sun, and heat, so the longevity is shorter. Demi-permanent sits in between: it uses a small amount of peroxide to slightly open the cuticle and allow some diffusion, so it lasts longer than direct semi-permanent but still fades with washing. The key idea is that permanent oxidative color creates new, bound pigment inside the hair, whereas direct dye relies on depositing pre-formed pigments with limited durability.