Mixing henna powder for your hair is the same as it is when
mixing for skin. Just as you need to leave the paste on your
skin for hours you will also need to leave the paste (or mud) on
your hair for hours.
Once you have applied the paste on your hair, wrap your scalp
with clingfilm and put a warm hat or towel over your head. After
6 hours wash it out by wetting it thoroughly. Usually there is
dried paste that comes out easier if you use some conditioner to
loosen it up. After all the paste is rinsed out of your hair it
doesn't feel soft and silky immediately. That seems to occur a
few days later.Henna won't completely change the color of your
hair. It will make it red but the color is more of a
transparency over your hair.