* How it works: 20 volume developer (6% hydrogen peroxide) is primarily used for lifting hair color and opening the hair cuticle. However, when used with a darker hair dye, it helps the dye penetrate the hair shaft more effectively, which can contribute to a more intense color deposit and therefore, a darker result.
* Darkening Power: A lot depends on the dye used, your hair texture, and how porous your hair is. In ideal circumstances, yes, it can darken by up to 3 shades, especially on hair that is naturally light or has been previously lightened.
* Important Considerations:
* Dye Choice: The dye you use is crucial. A demi-permanent or permanent dye formulated for darkening will work best.
* Porosity: Highly porous hair will absorb more dye and darken faster.
* Underlying Tone: Your starting hair color and its underlying tones will influence the final result.
* Lighter Developers: If you're only darkening by 1 or 2 shades, you could even use a lower volume developer like 10 volume (3% hydrogen peroxide).
In short, 20 volume developer assists in the darkening process by helping the dye penetrate the hair shaft. If you want to achieve a darker hair color, consider consulting with a professional hairstylist. They can assess your hair type, choose the appropriate dye and developer, and ensure the desired outcome while minimizing damage to your hair.