Yooo so I saw you liked my post, so can I ask you some advice? How frequently can I reapply the bleach, because I have a rapid growing black unibrow. Thank you!
I find that it is most helpful to let as much of your eyebrow hair grow out as possible before bleaching. If you tweeze or trim, you are encouraging regrowth, which will be dark. I don't recommend more than an hour's worth of bleaching in a single day, but my eyebrows and skin tolerated that fine, and if I had to do another 20-minute process I would have waited a few days and done some conditioning treatments on my brows before proceeding.
Eventually the tips of your brows will start to break off if you bleach very aggressively. Or you could pull a Michelle and accidentally melt them off multiple times -- they do grow back fast. I just let myself rock the salt and pepper look for a bit, and the last time I had white eyebrows, it took several months for all the dark growth to return.