Pour a small amount of tattoo ink into a sterile, disposable ink well or cup. Make sure the cup is large enough to hold the amount of ink you need to complete the shading, since having to mix more ink in the middle of a tattoo leads to inconsistent color.
Add the diluting agent. Water, 90 percent rubbing alcohol or white tattoo ink are all diluting agents used to create a lighter tone for shading. Mix or shake the ink well to distribute the pigment and diluting agent evenly in the mixture.
Test the mixture by putting a few drops onto a clean paper towel. The color should be consistent with no streaks or variation. If there are streaks, variations or the color is not correct, continue adding a diluting agent and mix until the desired consistency is achieved.