Also you d use it to stay anywhere around the level your hair already is or to lift 1 2 levels.
Hair color developer 20 vs 30.
Without the developer you would never achieve a significant changes in the color of your hair.
The hair color and the developer are mixed in a certain ratio to form a tint mixture which is then applied to the hair.
Choose a 30 volume developer when you want a developer that is stronger for a lighter and deeper color.
For slightly bigger changes in hair color opt for volume 20 developer which will change your color by 1 to 2 shades.
30 volume 9 developer.
You could upgrade to volume 30 to change your color 3 to 4 shades but keep in mind it can damage thin or fine hair.
For light colored hair such as light brown to a normal dark brown you can use a 20.
First off it is optimal for covering grey hair.
The 30 volume developer also works like 20 volume but it will lighten the hair s original color by two to three and is more efficient when the desired color is no more than two levels lighter than the original color.
Mixing ratio is usually 1 1 1 1 5 or 1 2 for an extra strong lightening effect.
But if your hair is a very dark brown that looks almost close to black you would use a 30 or maybe even a 40 if.
20 volume developer 20v 6 peroxide is the most commonly used.
30 volume developer 30v 9 peroxide will lift the hair up to 3 levels higher and is commonly used with lightener.