Yes, xeon, it is possible to do it, I would never say it is not possible to bleach hair to white, I do it all the time. but the factories do not like to bleach black hair down to white as it significantly weakens the hair....that is a fact. bleaching black hair to white, there is no way that the hair cannot be compromised somewhat.
I'm just stating what I know about some factories, I have seen pieces where people say "the knots were not bleached at all" and then get them and they are perfectly done. I do however realize that the factory, can at times, drop the ball and not bleach them and this could very well be the case with this poster....but I'd bet dollars to donuts that the knots are bleached.
I highly recommend that if you have black hair, order the front of the hair to be color #22 blonde and color it black when it comes in, that way the knots are real light.......I do this for many of my customers and have recommended that if you are fussy at all about knots, for others to order this way also. its a perfect look and easy to color just the front of the system hair.
DebbieS.