Letterpress printing is a technique of relief printing using a printing press. A worker composes and locks movable type into the bed of a press, inks it, and presses paper against it to transfer the ink from the type.
In practice, letterpress also includes other forms of relief printing with printing presses, such as wood engravings, photo-etched zinc “cuts” (plates), and linoleum blocks, which can be used alongside metal type in a single operation, as well as stereotypes and electrotypes of type and blocks. With certain letterpress units it is also possible to join movable type with slugs cast using hot metal typesetting.
Letterpress printing was the normal form of printing text from its invention by Johannes Gutenberg in the mid-15th century until the 19th century and remained in wide use for books and other uses until the second half of the 20th century. Letterpress printing remained the primary way to print and distribute information until the twentieth century, when offset printing was developed, which largely supplanted its role in printing books and newspapers. More recently, letterpress printing has seen a revival in an artisanal form.
In about 1440, Johannes Gutenberg is credited with the invention of modern movable type printing from individually cast, reusable letters set together in a form (frame or chase). He also invented a wooden printing press, based on the extant wine press, where the type surface was inked with leather covered ink balls and paper laid carefully on top by hand, then slid under a padded surface and pressure applied from above by a large threaded screw.
Later metal presses used a knuckle and lever arrangement instead of the screw, but the principle was the same. Ink rollers made of composition made inking faster and paved the way for further automation.
1917 press room, using a line shaftpower system. At right are several small platen jobbing presses, at left, a cylinder press.
With the advent of industrial mechanisation, inking was carried out by rollers that passed over the face of the type, then moved out of the way onto an ink plate to pick up a fresh film of ink for the next sheet. Meanwhile, a sheet of paper slid against a hinged platen (see image), which then rapidly pressed onto the type and swung back again as the sheet was removed and the next sheet inserted. As the fresh sheet of paper replaced the printed paper, the now freshly-inked rollers ran over the type again. Fully automated 20th-century presses, such as the Kluge and “Original” Heidelberg Platen (the “Windmill”), incorporated pneumatic sheet feed and delivery.
Rotary presses were used for high-speed work. In the oscillating press, the form slid under a drum around which each sheet of paper got wrapped for the impression, sliding back under the inking rollers while the paper was removed and a new sheet inserted. In a newspaper press, a papier-mâché mixture called a flong was used to make a mould of the entire form of type, then dried and bent, and a curved metal plate cast against it. The plates were clipped to a rotating drum and could print against a continuous reel of paper at the enormously high speeds required for overnight newspaper production. This invention helped aid the high demand for knowledge during this time period.