Ink paintings are done with a liquid that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing with a pen, brush, or quill. Ink can be a complex medium, composed of solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate matter, fluorescers, and other materials.

The components of inks serve many purposes; the ink’s carrier, colorants, and other additives control flow and thickness of the ink and its appearance when dry.

Source: Wikipedia