Most interesting!I remember that we used this technique at school in art education many years back .. but of course not with your expert hand.It gives such a haunted look.Maybe you should try it on Grigori Perelman ( Григорий Яковлевич Перельман )probably the most outstanding and yet most unknown genius of this milennium (unknown by his own choice partly )Perelman has enough hair to give you a real challenge.Here is an old photogood luck. (maybe he bcome more knwon this way )This is probably a newer one [link] Maybe he gets more known this way. Good luck.