Question: can you lighten hair with 20 volume developer?
Answer: You can mix 20 and 30 volume developer. The 20 volume developer has the power to lighten your hair 1 to 2 shades while 30 volume developer will shift your hair 3 to 4 shades. However, you should never use anything stronger than 30 volume developer at home. Box dyes usually come with 20 volume developer.