Some tribal cultures still create tattoos by cutting designs into the skin and rubbing the resulting wound with ink, ashes or other agents. This may be an adjunct to scarification. Some cultures create tattooed marks by "tapping" the ink into the skin using sharpened sticks or animal bones. Traditional Japanese tattoos (irezumi) are still "hand-poked," that is, the ink is inserted beneath the skin using non-electrical, hand-made and hand held tools with needles of sharpened bamboo or steel.
The most common method of tattooing in modern times is the electric tattoo machine. Ink is inserted into the skin via a group of needles that are soldered onto a bar, which is attached to an oscillating unit. The unit rapidly and repeatedly drives the needles in and out of the skin, usually 50 to 3,000 times a minute.
Permanent Cosmetics
Permanent makeup is a cosmetic technique which employs tattoos (permanent pigmentation of the dermis) as a means of producing designs that resemble makeup, such as eyelining (eye shadows and mascara) and other permanent enhancing colors to the skin of the face, lips and eyelids. It is also used to produce artificial eyebrows, particulary in people who have lost it as a consequence of old age, disease, such as alopecia, chemotherapy or a genetic disturbance, and to disguise scars and white spots in the skin such as in vitiligo. It is also used to restore or enhance the breast's areola, such as after breast surgery.
"Natural" Tattoos
According to George Orwell, workers in coal mines would wind up with characteristic tattoos owing to coal dust getting into wounds. This can also occur with substances like gunpowder. Similarly, a traumatic tattoo occurs when a substance such as asphalt is rubbed into a wound as the result of some kind of accident or trauma. These are particularly difficult to remove as they tend to be spread across several different layers of skin, and scarring or permanent discoloration is almost unavoidable depending on the location. In addition, tattooing of the gingiva from implantation of amalgam particles during dental filling placement and removal is possible and not uncommon.
Temporary Tattoos
Temporary tattoos are a type of body sticker, like a decal. They are generally applied to the skin using water to transfer the design to the surface of the skin. Temporary tattoos are easily removed with soap and water or oil-based creams, and are intended to last a few days.
Other forms of temporary "tattoos" are henna tattoos, also known as Mehndi, and the marks made by the stains of silver nitrate on the skin when exposed to ultraviolet light. Both methods, silver nitrate and henna, can take up to two weeks to fade from the skin.
Dyes and Pigments
For the tattooing, a wide range of dyes and pigments can be used; from inorganic materials like titanium dioxide and iron oxides to carbon black, azo dyes, and acridine, quinoline, phthalocyanine and naphthol derivates.
Iron oxide pigments are used in greater extent in cosmetic tattooing.
Recently, a blacklight-reactive tattoo ink using PMMA microcapsules has surfaced. The technical name is BIOMETRIX System-1000, and is marketed under the name "Chameleon Tattoo Ink". This ink is reportedly quite safe for use, and claims to be FDA approved for use on wildlife that may enter the food supply.
http://www.tribal-tattoos.co.uk/article-tattoo-procedure.php
