Ink | Research & Encyclopedia Articles

Ink

Ink is a combination of a coloring agent called pigment (or dye) with a liquid called a vehicle which also contains oils, resins, and solvents. Throughout history, ink has been made from many different colored juices and extracts of plants and animals as well as synthetic materials. The use of ink for writing and printing dates back to 3200 b.c., when the Egyptians used a mixture of lampblack (a fine soot produced by the incomplete combustion of oils and other carbons) suspended in vegetable gum. Both the Egyptians and the Greeks used iron oxide to make red ink from about 2800 b.c., although this was employed in marking linen rather than for writing. The ancient Chinese were making both red ink (from mercury sulfate) and black ink (from iron sulfur mixed with sumac tree sap) from 2000 b.c.; like the Egyptians, they made their ink into a solid block or stick that would be mixed with water when used. The ancient Romans developed a purple ink called encaustum, from which the word ink is derived, and also made a dark brown ink called sepia from dried, powdered cuttlefish ink-sacs.

Iron-gall inks were first noted in Italy in the seventh century a.d. and were primarily used during the Renaissance (fourteenth through sixteenth centuries) but were prone to fading. It was not until the seventeenth century that Europeans made ink with a mixture of tannic acid from tree bark and iron salt--a recipe that formed the basis for the blue and black inks still used today. About 1450, when the printing press was first developed, printing inks were made of varnish or linseed oil with lampblack added. The first patent for colored ink was granted in England in 1772. Invisible inks were developed in the mid-1800s. These inks were usually milk, whey, or sugar solutions, which, when exposed to heat or light, turn brown and visible. In the nineteenth century, chemical drying agents were developed that allowed easier use of a wider range of pigments for colors.

Technological developments of the twentieth century have made the manufacture of ink increasingly complex. Aniline dyes, developed in 1926, extend the range of color printing allowing application to plastics, fabric, and other substances; such dyes are frequently used in indelible (irremovable) ink. Synthetic dyes are now used for printing inks in place of the natural substances formerly relied upon. During the oil crisis of the 1970s, newspaper publishers began researching possible replacements for the petroleum distillates that formed the basis of the ink they used. In 1987, General Printing Ink began marketing a soybean- based ink. Use of this kind of ink has increased during the 1990s, particularly because it does not produce as much hazardous waste as petroleum-based ink when it is discarded. In the late 1990s, the biodegradability of soy inks increased as the ratio of soy oil to pigment improved. (Pigments are still petroleum-based, which is the primary source of hazardous rate.) The American Soy Association claims that more than one-third of all newspapers now use soy-based ink. Other advantages of soy ink include its capacity to produce brighter colors, its extended mileage (i.e., more can be printed with less ink), its renewability, and the fact that recycling paper printed with soy ink produces a higher-than- usual quality paper. Despite its higher cost, soy ink seems to be an increasingly popular choice for environmentally concerned publishers.

In the late 1997, researchers at the Massachusetts Institute of Technology announced a new ink-related technology that could change the face of printing. Scientists lead by Joseph M. Jacobson have developed a dynamic particle ink technology. Instead of an endless supply of ink being printed on an endless supply of paper, a single sheet of reusable paper would have two layers special electronic ink inside. One would be transparent and receive page data sent via radio waves; the other, comprised of microencapsulated particles, would used on the imaging of the actual page. Though this technology is only in its infancy, it represents one possible future of ink.