These drawings are White Charcoal Pencil on Black Artagain Paper.
This type of drawing is one of my personal favorites. It is also a different type of challenge to draw. You could look at it as the opposite of a regular drawing on white paper. Instead of filling in the shaded areas, you fill in the light areas. It takes a little getting use to because once you get accostomed to shading in the dark areas, it's like your brain resists doing the opposite. My first couple of drawings were a real challenge but now my brain seems to understand the concept much better and I'm drawing them with ease.

Unfortunately, art suppply manufacturers don't seem to see enough demand to make different values in white leads like they do with black. That creates another challenge in itself, you basically have to draw all your different values with one pencil. Its a lot trying to draw a masterpiece with a standard no.2 pencil! Hopefully, one day, they will start making them in different values.

If you decide to take on this type of drawing, just be patient with yourself. Give yourself time to really grasp the concept of drawing oppositely. I shade darker white values by filling them in very lightly, then I use a q-tip applicator to smear the charcoal. You can always test before you actually draw. Tyhe key thing here is PATIENCE! Good luckand have fun!

                                                                                                     - hre2art
In the picture above, you can see me drawing Prince using a General's White Charcaol Pencil 558. I also use a Sharpie Peel-Off China Marker. I only use the Sharpie for very fine white lines, I can easily shapen it to a very fine point but the value is about the same as the General's.