Yes, combining ''equal parts'' of 30 V. and 10 V. developers will make 20 V. developer.
You can mix equal parts of 20 volume developer and 0 volume developer to make a 10 volume developer solution. The resulting mixture will have an average volume of 10 developer.
To make 10 volume developer from 20 volume developer, you can mix equal parts of 20 volume developer and distilled water. For example, mix 1 part of 20 volume developer with 1 part distilled water to create 10 volume developer.
To create a 30 volume developer solution with a 40 and 30 volume developer, you can mix equal parts of each developer together. For example, mix 1 part 40 volume developer with 1 part 30 volume developer. This will result in a 35 volume developer solution, which is close to 30 volume. It is important to perform a strand test before using the mixed developer on your hair to ensure it is the desired strength.
No, you cannot make 30 volume developer out of 40 volume developer. You would need to dilute the 40 volume developer with either distilled water or a lower volume developer to achieve the desired 30 volume strength.
No, 20 volume developer and 40 volume developer cannot be mixed to create 20 volume developer. Mixing them will result in a product with a higher volume developer concentration than either of the original solutions. It is not recommended to mix different volumes of developer as it can affect the outcome of your hair treatment.