Gray wash is a method of shading tattoos using only black or gray inks. The various techniques of preparing and applying gray wash allow tattoos to have the same depth and shading as pencil drawings. How tattoo artists prepare and apply gray wash is largely a matter of individual style and technique -- some tattoo artists refer to a type of ink as gray wash while for others gray wash is the name of a technique that includes the handling of the machine. You can make a tattoo ink gray wash using a variety of methods.
Create a series of gray shades by diluting black tattoo ink. Make a series of four ink caps -- drop one drop of black ink into the first cap and then add an additional drop to each successive cap. Fill each of the four caps with clean water, drop by drop. Add one more cap with undiluted black ink for line work. Clean the needle tube in between using different gray tones like you would with different colors. Many professional tattoo artists use a technique like this one; an equal number of professionals believe it is a mistake to ever dilute your inks and use a different technique.
Create a special gray wash ink using vodka, propylene glycol, glycerin and black pigment.
Purchase a premade gray wash from a tattoo ink distributor. Kuri Sumi is one brand of commercially available gray wash; it is suggested to read a tutorial on using Kuri Sumi gray wash (see the Resources).
Work with the black ink by diluting it directly in a cap of water. Dip the needle in the cap of black ink then follow it with a dip in a cap of plain water. Additional quick dips in the water adjust your shade. Set the machine low, and work the skin slowly. Check the color of your shade on a paper towel before applying. Very few professional artists use this technique.