Here's a breakdown:
* Permanent Hair Color: 20 volume developer is a common choice for permanent hair color. It provides adequate lift (lightening) and deposit of color, suitable for covering gray, going a shade or two lighter or darker, or changing the tone of your hair.
* Demi-Permanent Hair Color: While you *can* use it, 20 volume might be more powerful than necessary for demi-permanent color. Demi-permanent color is designed to deposit color without lifting (lightening) your natural hair. Using a 10 volume developer is usually recommended for demi-permanent color, as it gently opens the hair cuticle just enough for color deposit. A 20 volume developer can slightly lift, which you may not want with demi-permanent color. Using 20 volume could also cause more damage than necessary.
* Semi-Permanent Hair Color: Semi-permanent color doesn't require developer. It deposits color on the surface of the hair and fades with washing. Mixing it with developer will not improve the color result and may actually damage your hair.
* Bleach: While 20 volume is sometimes used with bleach, it's generally considered on the weaker side for significant lightening. It's a good choice if you're aiming for a subtle lift or have delicate hair. For more dramatic lightening, you'll typically need a higher volume developer.
Important Considerations:
* Hair Condition: If your hair is damaged, porous, or previously processed, a lower volume developer (like 10 volume) is generally safer, even with permanent hair color. 20 volume could cause further damage.
* Desired Result: Consider how much lift you need. If you only want to go a shade or two lighter or cover gray, 20 volume is often suitable. For more significant lightening, you might need a higher volume, but that comes with increased risk of damage.
* Hair Color Brand Instructions: Always follow the specific instructions provided by the hair color brand you are using. They will recommend the appropriate developer volume for their product. Different brands formulate their colors differently, and using the wrong developer volume can lead to unexpected results or damage.
* Patch Test: Perform a strand test before applying color to your entire head. This will help you see how the color will look and assess any potential damage.
In summary:
* Yes, you *can* use 20 volume developer with many hair colors, especially permanent ones.
* However, it's crucial to consider your hair condition, desired result, and the specific instructions of the hair color brand.
* Using the wrong developer volume can lead to undesirable results or damage.
* When in doubt, err on the side of caution and use a lower volume developer or consult a professional.