Permanent hair dye is permanent because it alters the natural hair pigment by depositing color within the hair follicle, and this process is not easily reversible.
The Mechanism of Permanent Hair Dye
Permanent hair color doesn't just coat the hair; it actually changes its structure. Here's how:
- Cuticle Opening: The dye formula works by opening the hair cuticle. This outer layer of the hair shaft is made up of overlapping scales.
- Penetration: Once the cuticle is opened, the dye formula can penetrate into the hair follicle (also called the cortex).
- Pigment Replacement: Inside the cortex, the dye molecules react to add new color, replacing or combining with the hair’s natural pigments.
- Permanent Color Deposition: The color molecules are permanently deposited within the hair shaft, making the color last until the hair grows out or is cut off.
Why It's Different from Temporary Dyes
- Temporary dyes only coat the hair shaft and wash out easily.
- Permanent dyes, on the other hand, permanently alter the hair's inner structure.
Practical Insights
- Growth is Key: Since the color is permanent, the treated hair will always hold the dye until it grows out.
- Touch-ups are Common: Because of the new growth at the roots, many people require periodic touch-ups to maintain consistent color.
- Color Fading: Although the color is permanent, it can gradually fade due to sun exposure, washing, and other environmental factors. Using color-safe shampoos and conditioners can help to slow down this fading.
Table Summarizing Dye Types
| Dye Type | How It Works | Permanence |
|---|---|---|
| Temporary | Coats the hair shaft | Washes out easily |
| Permanent | Penetrates and changes hair follicle | Lasts until growth |
