Tattoo Needles and the Geometry of a Hole

Tattoo Needles and the Geometry of a Hole
There are a few reasons why angle matters. One has to do with the vector of the force. When you're tattooing at a 90 degree angle, the vectors are pointing straight down and are absorbed by the skin. However, when you tattoo at a 45 degree angle, the vectors are pointing up and out, or away from the skin, which means that they compress the skin less.
The other reason has to do with geometry. When you come at the skin from an angle, the needle is creating an elliptical hole. This elliptical shape allows for more ink to be deposited in one pass.