The introduction of solvent ink for digital printing a couple of years ago, ink jet printing for outdoor applications were made possible. These systems are very popular in the sign industry as well the T-shirt industry however;

Water-based inks are the most common inks used for digital printing because these are not or little detrimental for people and nature. Almost all inkjet printers in office or at home are using this type of ink. The water is solely used to transport the dye to the media.

Read a story solvent vs. water-based inks here...