Bleaching hair in large amounts is a real challenge,
While bleaching few kilos of hair in bleach bath, we end up getting all kinds of hairs as seen in the video.
Depends on hair nature, texture, and the hair life-history.
Usually virgin uncolored hairs are easily bleached to light blondes,
color toned hairs might be lifted up to light browns and etc,.
and black tinted hairs, usually does go not higher than medium rbowns,...
So blending helps us to create smooth monotone nice looking hair ponytails