How many levels of gray coverage and lightening does 20 volume achieve?

Twenty volume developer is typically used for hair lightening and gray coverage. It is known to lift the hair color by approximately 1 to 2 levels. This means that if you start with a darker shade, using a 20 volume developer would allow you to achieve a lighter color that is either one or two shades lighter.

Additionally, for gray coverage, 20 volume developer is effective because it has enough strength to help the color penetrate the hair shaft, allowing for coverage of gray hairs without overly lightening the natural hair.

The other options suggest higher levels of lift that are not achievable with a 20 volume developer, as greater amounts of lift typically require a higher volume developer, such as 30 or 40 volume. Therefore, the specified range of 1 to 2 levels accurately reflects the lifting capability of a 20 volume developer in both lightening and gray coverage contexts.