By the end of the 2nd century AD the Chinese had invented paper, ink and a block with a picture or letters cut into it, the basic requirements for printing. The blocks were made of wood, and text was engraved on them by cutting around the characters so they stood out in relief. By the 14th century, individual blocks had been carved for each of the 80,000 Chinese characters. They could be arranged in any order to make up a page, the principle of movable type.
The really decisive advances, however, were made in Europe in around 1450, by Johannes Gutenberg and Johann Fust. Both goldsmiths by trade, they used metal type and a vice-like press to transfer the ink from the blocks to the paper. Each letter was separately cast, using a low melting point alloy of lead, tin and antimony. The letters were arranged side by side along a strip of wood called a stick to form words, and the lines were justified by inserting small pieces of lead between the words. By 1448 Gutenberg had printed the Bible in Latin, each page taking a printer a day to set in type. A similar process was adopted by the Englishmen William Caxton. He printed the first book in English in 1475.
Printing in hot metal lasted more than 500 years. Its speed was improved by inventions such as the Linotype machine, produced in 1884 by Ottmar Mergenthaler in the USA, which could cast a whole line at once from individual letters typed by the operator on a keyboard. It was used mainly for newspapers. Its principal rival was the Monotype machine, invented in 1887 by Tolbert Lanston, also in the USA.
The monotype operator keyed in the text, which was coded into a punched tape, together with information about the spaces between words needed to justify the line. This information came at the end of each line, but the tape was fed to the typecaster backwards, so that the correct spacing was known before the line was cast. The Monotype machine produced high quality jobs and was used for a wide range of printing jobs.
Today typesetting, as well as other stages in the production of printed matterial, has been almost entirely taken over by computers.
Three methods of printing are of particular significance. In letterpress printing, the method used by Guttenberg, the raised surfaces of the typeset page are covered in ink by rollers, and paper is pressed against it in a press to transfer the image.
The principle of lithography, which has almost entirely taken over from letterpress, depends on the fact that water and grease do not mix. The images to be printed are transferred to flexible metal plates photographically, in such a way that the areas to be printed consist of chemicals that attract ink and repel water, while the blank areas attract water and repel ink. First water and then ink is applied to the plate; all of the ink congregates in the areas of the image, and can be transferred to paper in a rotary press.
A third technique is widely used for printing colour supplements and magazines. In gravure, the image is etched on a plate photographically, forming cells whose depth depends on the intensity of the colour.
