FROM GROLLIER'S INTERNATIONAL ENCYCLOPEDIA.
Printing, in its broadest sense, is any process whereby one or more identical copies are produced from a master image. The master image can range from an inscription engraved in stone to an illustration cut into a wood block or a text stored as digital information in a computer. Image transfer, from master to copy, is usually accomplished with ink, and the transferring agent is most often the printing press. The development of new technologies has blurred traditional definitions of printing, however: office copiers, for example, reproduce master images using electrostatically charged graphite toner.
The routine, though rudimentary, reproduction of textual matter first occurred near the beginning of the 8th century AD, when the Chinese began to experiment with the printing of relief, or raised, images cut in wood blocks. During the 11th century both the Koreans and the Chinese experimented with the manufacture of movable type made from clay and wood and, later, from bronze and iron. Although the notion of movable type was a major advance in printing technology, the complex characters that formed the written languages were too difficult to produce as individual pieces of type.
The German Johann Gutenburg, working 400 years later, enjoyed the advantage of a simple alphabet, and he worked out a method of casting type and printing so successful that its fundamental principles were not improved until well into the 19th century. Gutenberg's first book, a Latin Bible, was completed about the year 1455.
The essential features of Gutenberg's invention included lead-alloy type cast in an adjustable mould, oil-based inks, and a wooden printing press in which a large screw moved the upper part, the platen, up or down against paper laid over type on the lower surface, the bed. Later improvements to Gutenberg's screw press were largely devoted to increasing impression power, improving the clarity of the printed image, and devising a return mechanism for the press handle. About 1800, Charles, 3d Earl Stanhope, developed an all-metal press, and in 1813, George Clymer dispensed with the screw, substituting instead a system of power-multiplying levers. Although 19th-century designers continued to improve the efficiency of the iron hand press, its practical limits were soon reached. Until recently, though, small-job printers continued to use the platen press, invented in the early 19th century, in which the flatbed was vertically positioned and power was supplied by a foot treadle or by steam.
In 1811, Friedrich Koenig patented the first Flatbed cylinder press, using a revolving cylinder instead of a flat platen to press sheets of paper against a flatbed of type. The bed moved under inking rollers between each cylinder impression. A steam-powered Koenig press installed by the Times of London could print over 1,000 sheets per hour. Even greater speed came with the invention of the rotary press in 1844 by the American Richard Hoe. Hoe attached metal type to the surface of a cylinder, thus replacing the flatbed. Several small cylinders supplied the pressure. The web press, a rotary press that printed a continuous reel of paper, was patented (1835) by Rowland Hill of England. The first operating web-fed rotary press was built in the United States in 1837.
The difficulty of making curved relief printing plates slowed the acceptance of the rotary press. By the 1870s, however, curved STEREOTYPE plates could be accurately cast, and they replaced Hoe's metal type. From that point until well into the 20th century, the press of choice--especially for newspaper publishers--became the automatic rotary cylinder press, printing both sides of a continuous web of paper. Steam provided power for the early machine presses; electric power was used from the end of the 19th century.
Most printing technology was based on letterpress, the printing of images that projected above nonprinting areas. In 1796, Aloism Senefelda invented a planographic, or flat-plane, printing process later called Lithography. He found that an image, no matter how detailed, that was drawn with a greasy substance on the face of a water-absorbent stone and then inked could be printed onto paper with absolute fidelity. Lithography was ideally suited for illustration and enjoyed a phenomenal popularity during the 19th century, especially for colour printing, which required a separate stone to print each colour. Eventually, it was found that the image on the stone could be transferred, using a special starch-coated transfer paper, from the stone to a metal plate that was used for the actual printing.
Lithographic metal plates had only rarely been used for commercial printing, in part because the image on the plate was often worn through by the printing paper. In 1904 an American printer, Ira S. Rubel, accidentally discovered that the lithographic image could be transferred, or offset, to a rubber cylinder that could then print as perfectly as the plate and would last indefinitely. Rubel's three-cylinder offset press was the first in the field of offset lithography, which would become the most popular printing process because of its economy, long plate life, and ability to print on many different textures.
Halftone colour printing, the process still used today to reproduce full colour, was introduced in the 1890s, but many years passed before its full potential was realized. Although colour reproduction theory was fairly well understood, the lack of colour film restricted colour work to studios where the necessary separation negatives had to be made directly from the subject, under the most exacting conditions. Reliable colour film became available in the 1930s and '40s, and colour reproduction grew both more common and more accurate.
Throughout the 19th century, attempts to mechanize the processes of type making (casting) and composition (typesetting) resulted in a number of ingenious inventions, some incorporating both casting and composing operations.
Thelinotypemachine of Ottmar Mergenthaler and themonotype invented by Tolbert Lanston, both introduced in 1887, proved to be so clearly superior to rival devices that no better mechanical systems for letterpress composition were ever developed. The Linotype was a keyboard-operated machine that composed and cast a justified line of type and was particularly suitable for newspapers. The Monotype's keyboard produced a punched tape that instructed a separate type caster to produce individual characters in complete, justified lines. The Monotype was used largely for book printing.
The type used to make offset lithographic plates originally came from proofs taken from letterpress type. As offset printing grew in popularity, a more efficient method was sought. In 1954 the Photon machine became the first commercially successful electronic photocomposition system. Its key elements, which were used by later machines as well, were a stroboscopic light source and a spinning film matrix disk through which photographic film was exposed with images of type previously composed on a keyboard.
Computers play a vital role in nearly every area of printing, from typesetting to on-press control of the many variables subject to change during a print run. Digital storage and manipulation of text, whether at a word-processing station or a typesetting terminal, were early computer-printing operations. When paired with long-distance digital transmission technology, numerous possibilities became evident.
When an issue is ready for printing, a central production facility can electronically transmit the entire contents to regional printing plants, speeding up both printing and distribution. Increasingly powerful systems can now provide the vast storage required for very high-resolution graphics, as well as providing methods for sophisticated image manipulation. The operator of a typical system can scan a colour photograph into the computer, and then call the image up to a display screen where a number of editing processes can be employed: rotation of the image, increased shading, colour correction or colour changing, the moving of parts of the image or its entire deletion. The final, edited image is sent to an output laser scanner, which produces a set of colour film separations that will be used to make the printing plates.