Q) Layering colors seems to be an effective way of getting a painterly look to your tattoos, but how do you know when the skin has had too much before you start chewing it up and running the risk of scarring?
A) Layering color this way is actually a good way to prevent trauma, since you can run your equipment with way less force than if you are trying to pack it in solid with one pass. That's the first important point- when layering, you don't want each pass to saturate the skin. Try to keep in mind roughly how many passes of different colors you plan on layering in a given area, and work accordingly... if you plan on layering 3 colors, for example, each pass should only be 1/3 as solid as if you were packing in only one color. This way, as long as you work with smooth overlapping hand motions, the pattern of holes in the skin will be no more closely packed than with one solid pass. It's important for all tattooists, though, to develop a good intuitive feeling for when the skin is approaching its limits; you will learn to look for certain telltale signs of trauma, such as small trenches, roughness or that "wet tissue paper" look that the skin takes on when it's been hit too many times. Ultimately, it's a matter of paying close attention and developing good habits.