Ink is a gel, sol, or solution that contains at least one colourant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. Thicker inks, in paste form, are used extensively in letterpress and lithographic printing.
Ink can be a complex medium, composed of solvents, pigments, dyes, resins, lubricants, solubilizers, surfactants, particulate matter, fluorescents, and other materials. The components of inks serve many purposes; the ink's carrier, colorants, and other additives affect the flow and thickness of the ink and its dry appearance.
In 2011, worldwide consumption of printing inks generated revenues of more than 20 billion US dollars. Demand by traditional print media is shrinking; on the other hand, more and more printing inks are consumed for packaging.[1]
Many ancient cultures around the world have independently discovered and formulated inks for the purposes of writing and drawing. The knowledge of the inks, their recipes and the techniques for their production comes from archaeological analysis or from written text itself. The earliest inks from all civilizations are believed to have been made with lampblack, a kind of soot, as this would have been easily collected as a by-product of fire.[5]
Ink was used in Ancient Egypt for writing and drawing on papyrus from at least the 26th century BC.[6] Egyptian red and black inks included iron and ocher as a pigment, in addition to phosphate, sulfate, chloride, and carboxylate ions; meanwhile, lead was used as a drier.[7]
Chinese inks may go back as far as three[8] or maybe four millennia,[9] to the Chinese Neolithic Period. These used plants, animal, and mineral inks based on such materials as graphite that were ground with water and applied with ink brushes. Direct evidence for the earliest Chinese inks, similar to modern inksticks, is around 256 BC in the end of the Warring States period and produced from soot and animal glue.[10] The best inks for drawing or painting on paper or silk are produced from the resin of the pine tree. They must be between 50 and 100 years old. The Chinese inkstick is produced with a fish glue, whereas Japanese glue (膠 "nikawa") is from cow or stag.[11]