Black and Grey / Realistic Tattoo
Black and grey tattoos are generally believed to have originated within prison systems, where inmates had no access to colored ink.
The technique was brought to mainstream tattoo shops by Jack Rudy and his mentor, Charlie Cartwright. They perfected a single-needle tattoo machine to produce highly realistic shading in their tattoo designs. This technique works well for portraiture.
Black-and-gray is sometimes referred to as "jailhouse" or "joint style" and is thought to have originated in prisons where inmates had limited access to different materials; they resorted to using guitar strings for needles and used cigarette ashes or pen ink to produce tattoos.
Inmates would construct makeshift tattoo machines that were powered using the small motors available in tape players. Prisons generally prohibit inmates from tattooing, so these were likely to be done in secret.
During the late 1970s and early 1980s, jailhouse then became popularized in tattoo parlors outside of prison and was renamed "black and gray". Black and gray is also thought to have originated from the Chicano or cholo culture in Los Angeles.
Typically, black and grey tattoo work is produced by diluting the black ink with distilled water in varying proportions to create a "wash" that results in lighter shades. Gray shades can also be produced by mixing small amounts of black ink with white ink, which produces a thicker but brighter result and requires a slower application.