Tattoo ink is either water based, which makes them easier to mix and form new colors, or alcohol based, which allows for bolder colors. Distinctions can also be made between visible inks and UV ink, which can only be viewed under a black light.
Ink is deposited by a tattoo needle into the dermis, which is the second layer of skin. When a tattoo is viewed, it actually shows the ink through the top layer of skin, rather than directly.
Some people have allergies to tattoo ink, which is not regulated by the FDA. However, hypoallergenic tattoo inks are on the market, except in the color red.
Tattoo ink can be removed using surgical laser techniques. Short bursts of intense light break up the ink, which is then removed from the body via the immune system.
Some tattoo inks could contain potentially harmful material, such as Antimony, Arsenic, Beryllium, Cobalt, Lead, Nickel, or Selenium, which are all toxic metals. Always check with the tattoo artist to see what kinds of inks they use.