Permanent hair dye works by fundamentally altering the hair's structure, providing a color that will not wash out. Here's a breakdown of the process:
The Science Behind Permanent Hair Dye
Permanent hair dyes don't just coat the hair; they penetrate it. This process involves:
- Opening the Hair Cuticle: The dye solution, typically containing ammonia, first raises the hair's outer layer, called the cuticle. This allows the dye molecules to enter.
- Penetrating the Hair Cortex: Once the cuticle is open, the dye molecules travel to the hair's cortex, the inner layer where the hair's natural color resides.
- Bonding with Hair Structure: Inside the cortex, the dye molecules react with the hair's natural pigments. This reaction causes the new color to chemically bond to the hair structure, making it permanent.
Key Differences from Non-Permanent Dyes
| Feature | Permanent Hair Dye | Non-Permanent Hair Dye |
|---|---|---|
| Penetration | Enters hair cuticle and cortex. | Coats the hair strand. |
| Color Duration | Lasts until new hair grows out. | Washes out over time. |
| Chemical Process | Involves a chemical reaction within the hair. | Less intensive chemical reaction. |
| Hair Damage | Potentially more damaging to hair. | Less likely to damage hair. |
Practical Insights
- Because permanent dyes chemically alter the hair, they can be more damaging than temporary or semi-permanent options.
- The process often involves a developer (usually hydrogen peroxide) to activate the dye molecules.
- Due to the permanent nature of this color, you'll need to touch up the roots as new hair growth appears.
- The final color you achieve depends on your starting hair color, the developer used, and the chosen dye.
- It is important to follow manufacturer instructions and potentially do a strand test to check for allergic reactions or desired results.
In Summary:
Permanent hair dye works by penetrating the hair cuticle, entering the cortex and then chemically bonding, which results in the hair being permanently dyed. This is different from non-permanent dyes, which just coat the hair.
