Many commercially-printed books, brochures, business forms, catalogues, labels, letterhead, newspapers, magazines, posters, product packaging and stationery are produced using offset lithography. Other printing methods include flexographic, gravure, screen and digital or nonimpact printing. Lithography is popular due to its low cost and versatility, and the high quality of its results, which have smooth, clear images with no impressions left on the page.
Offset lithography creates clear, smooth, sharp images and text on a variety of materials. With traditional offset lithography, the blanket--that is, the part of the press which presses against the paper or printing surface--is made of a soft rubber which conforms to almost any paper surface or material, unlike systems which use inflexible metal plates for printing. Modern offset presses frequently use computer-to-plate systems, which further increase the clarity and sharpness of the image.
Lack of Impressions
Letterpress and gravure (intaglio, rotogravure or photogravure) printing characteristically leave impressions: raised or indented text and lines on the page, serrated edges and rings of ink. For some projects, leaving marks on the paper is seen as a sign of authenticity, but many manufacturers don't want readers distracted from the content of their message by the way it was printed. In addition, these impressions make stacks of printed items thicker, which can affect transportation and storage costs. Lithographic images lack these artifacts.
Lithography was initially invented by Alois Senefelder in 1798 to provide a lower-cost alternative to copperplate engraving. Much of the expense of printing with offset lithography comes from setup costs, and printing requires little maintenance. Offset lithography isn't cheaper for small projects. However, the unit cost of each page goes down as the quantity printed goes up, making offset lithographic printing the cheapest, most cost-effective method for producing commercial quantities of high-quality printed items.
Many sheet-fed lithographic presses print simultaneously on both sides of the paper, which decreases printing times. Some web press lithographic machines can print as many as 50,000 sheets per hour.
Lithographic printers use equipment for any length of press run. The slower, more precise sheet-fed lithographic presses are used for short- and medium-run printing like art reproduction, coupons, direct mail inserts, greeting cards and posters. The high-speed, more efficient web presses are used for medium- and long-run printing like advertising flyers, books, catalogues, magazines and newspapers. In addition, lithographic presses work not just on paper but on a wide variety of printing surfaces, including cloth, leather, metal, plastic and wood.