Unpopular opinion: the 10 minute processing rule for bleach is not as set in stone as I thought
Last month a rep for a color line showed me a chart saying bleach can keep lifting past the 10 minute mark and that the cap is really about how fast your developer dies, not some magic timer. I always pulled it at 10 like clockwork, which meant a few of my level 6 clients in the chair at Salon Lofts never got that last bit of lift. She had us test it on a swatch with 20 volume and we checked the tone every 5 minutes, and the change after 15 was small but real. Now I time by feel and strand test instead of watching the clock. Anyone else had a color rep hand them something that made them question a rule they learned in school?
Read somewhere that bleach keeps working til the developer runs out, so the timer thing is kind of a myth anyway. Watched a video where a guy checked his swatches every few minutes and saw the same slow change you're talking about. Take it with a grain of salt but strand testing always beats the clock in my book.