This is a fairly new technique in tattooing. It's all black ink shaded to gray. This can be achieved by diluting the ink as you go along. You will need a cap of blac ink and a cap of clean water. As you do your shading, work away from the darker side. In a flipping motion apply pressure and gradually lighten up on the pressure as you work away until you get the desired tone of shading that you want. This will take a lot of practice, so don't expect to be good at this technique when you first try it.
NOTE: When I do this wash effect I prefer to use a #14 round shader needle, then I come back with a #6 flat and feather out to get my desired tone. This will vary between artist and one's own personal preference. Always be careful not to over work the skin. It is the skin that holds the ink, not the flat tissue or the muscle tissue. So what I'm trying to say is you don't need to drill for oil.
