The process of printing allows people to make identical copies of texts and images by putting ink on paper. Printing began as a very slow procedure done by hand. With the invention of a machine called the printing press, printing became faster and easier. Modern computerized printing can produce hundreds of pages in minutes. Printing has many uses. Books, magazines, money, stamps, maps, posters, billboards, and labels are all created through the process of printing. Printing methodsBefore a page can be printed, the words and pictures on it must be arranged correctly. That process is called typesetting or composition. In traditional (not electronic) printing, an image of the final page is then transferred onto a plate. Printing plates are usually made of metal or rubber. All the copies of each page come from the plates, so it is important to check each plate for errors before printing. There are three traditional methods of printing: letterpress, intaglio, and offset. The newest printing method is electronic, or digital, printing. Letterpress printingLetterpress printing is the oldest method of printing with a machine. In letterpress printing the letters and pictures on the printing plate are raised. They are also reversed, as if seen in a mirror. Ink is applied to the plate, and then paper is pressed against it. The ink on the raised letters and pictures is transferred to the paper. For more than 400 years letterpress printing was the main method of making books and newspapers. Now it is mainly used for creating special paper products such as wedding invitations. Intaglio printingIn intaglio printing the letters and pictures are engraved on, or cut into, the printing plate. The letters and pictures must be in reverse. When ink is applied to the plate, it stays in the cut-out areas. When paper is pressed against the plate, the paper absorbs the ink from those areas. The printing plates originally used in intaglio printing were engraved by hand. Photogravure is a kind of intaglio printing that uses photographic methods to create the printing plates. Printers use photogravure to make both flat plates and printing cylinders. The intaglio process that uses printing cylinders is called rotogravure printing. Rotogravure is fast and good for printing photographs. It is used to print some catalogs and magazines. Offset printingOffset printing is the most common method of traditional printing. In offset printing the letters and pictures on the printing plate are not raised or engraved. Chemicals are used to form the image on the plate. The printing plates are dampened with water and then oil-based ink. Water sticks to the blank parts, and ink sticks to the image. The inky image is then transferred onto a sheet of rubber. From the rubber sheet the image is transferred onto paper. Because the image is transferred twice, the letters and pictures on the plate do not have to be reversed. Before electronic printing, most printing was done using the offset method. Electronic printingComputers have made printing faster and easier than ever before. Computers help with typesetting. They also help to create printing plates and to run printing presses. In electronic, or digital, printing—the newest printing method—traditional printing plates are not even needed. Using powdered ink, laser printers can transfer the image of a page that was created on a computer right onto paper. Some publishers use electronic printing companies to print their books. Many businesses and individuals use personal computers to design and print documents. HistoryPrinting started in China. By the 8th century AD the Chinese were using carved wooden blocks to make prints. They applied ink to the carved block and then pressed paper onto it. By the 11th century the Chinese were using individual blocks for separate characters (symbols that stood for words or ideas). The blocks, called type, could be moved around to print different words and sentences. Those Chinese blocks are known as the world's first movable type. In the 15th century a German inventor, Johannes Gutenberg, invented a wooden printing press. It was the first machine that could make copies of whole pages of text. Gutenberg combined several existing inventions. For the machine he copied the screw press, which was used to make wine and olive oil. From China he took the idea of movable type. Instead of parchment (animal skin) he made the prints on paper, which had also come from Asia. To make a print, Gutenberg arranged the type (metal blocks with raised, reversed letters on them) on a tray. He put ink on the type and laid a sheet of paper on top. He then used the machine to press the paper against the type. Because the type could be reused, Gutenberg could easily print many copies of a page—and even copies of a whole book. The printing press created a communication revolution. Before the invention of the printing press, the few people who could read and write copied books by hand. It was a slow process, so there were few books available. After the invention of the printing press, books could be printed, copied, and sold more quickly and cheaply. More people in Europe learned to read, and they demanded more books. Printing also allowed for the printing of paper money and the first newspapers. The printing press and printing methods improved over the years. By the 20th century machines could set the type for each page. In the mid–20th century computers made typesetting even faster. Computerized printing soon brought the biggest change to printing since the invention of the printing press. By the start of the 21st century people could use computers to design and print documents without movable type or a printing press. |