The processing time for 20 volume developer on dark hair varies depending on the desired level of lift and the hair's condition. Generally, 20 volume developer is used for lightening dark hair by one to two levels.
Here are some general guidelines:
- For a subtle lift: Leave the developer on for 15-20 minutes.
- For a more noticeable lift: Leave the developer on for 25-30 minutes.
Important Note: Always perform a strand test before applying developer to the entire head of hair. This will help you determine how long the developer needs to be left on for your hair type and desired outcome.
Remember: 20 volume developer is a powerful tool. Always follow the instructions on the developer bottle and use caution when handling it.
