The technician using the laser can not regulate the speed of the fading process. The more energy used the greater the tissue damage thus trapping more ink. It is better to allow the technician to treat more conservatively than aggressively, allowing the surrounding tissue to relax in the weeks following the treatment. Medium or fair skin patients react well because the light will be able to selectively target the ink instead of the dark skin. Dark ink that is not dense is favorable because the light is more attracted to darker colors so darker ink is fragmented better than yellow ink.
Density is also a factor, the more ink, the more there is to fade.
Superficial ink is also favorable because it is closest to the surface of the skin so the laser doesn't need to penetrate so many skin layers to get to it. Results are quicker. Areas such as the arm or chest have more blood flow and are a better vehicle for the immune system which is what removes the ink. Areas such as the ankle or fingers have poor circulation. There are many factors involved in laser tattoo removal, the physician must understand these parameters in detail.