Ink

Ink is a gel, sol, or solution that contains at least one colorant, 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 multiple purposes; the ink's carrier, colorants, and other additives affect the flow and thickness of the ink and its dry appearance.

Many ancient cultures around the world have independently discovered and formulated inks due to the need to write and draw. The recipes and techniques for the production of ink are derived from archaeological analyses or from written texts themselves. The earliest inks from all civilizations are believed to have been made with lampblack, a kind of soot, easily collected as a by-product of fire.

Ink was used in Ancient Egypt for writing and drawing on papyrus from at least the 26th century BC. Egyptian red and black inks included iron and ocher as pigments, in addition to phosphate, sulfate, chloride, and carboxylate ions, with lead also used as a drier.

The earliest Chinese inks may date to four millennia ago, to the Chinese Neolithic Period. These included plant, animal, and mineral inks, based on such materials as graphite; these were ground with water and applied with ink brushes. Direct evidence for the earliest Chinese inks, similar to modern inksticks, is found around 256 BC, in the end of the Warring States period; being produced from soot and animal glue. The preferred inks for drawing or painting on paper or silk are produced from the resin of the pine trees 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.

India ink was invented in China, though materials were often traded from India, hence the name. The traditional Chinese method of making the ink was to grind a mixture of hide glue, carbon black, lampblack, and bone black pigment with a pestle and mortar, then pour it into a ceramic dish to dry. To use the dry mixture, a wet brush would be applied until it reliquified. The manufacture of India ink was well-established by the Cao Wei dynasty (220–265 AD). Indian documents written in Kharosthi with ink have been unearthed in Xinjiang. The practice of writing with ink and a sharp pointed needle was common in early South India. Several Buddhist and Jain sutras in India were compiled in ink.

Cephalopod ink, known as sepia, turns from dark blue-black to brown on drying, and was used as an ink in the Graeco-Roman period and subsequently. Black atramentum was also used in ancient Rome; in an article for The Christian Science Monitor, Sharon J. Huntington describes these other historical inks:

About 1,600 years ago, a popular ink recipe was created. The recipe was used for centuries. Iron salts, such as ferrous sulfate (made by treating iron with sulfuric acid), were mixed with tannin from gallnuts (they grow on trees) and a thickener. When first put to paper, this ink is bluish-black. Over time it fades to a dull brown.