Can you explain what is the actual result when doubling the developer? As in high lifts when using double 30vol. or 40vol.? Also, you've mentioned using the high lifts with double 20vol.
I've read recently where a colorist used a permanent color with double 20vol. What results would this get, and is it even okay to do that?
Thanks for any insights.
By the way, are you teaching a color class in Chicago in October?