A platen (or platten) is a platform with a variety of roles in printing or manufacturing. It can be a flat metal (or earlier, wooden) plate pressed against a medium (such as paper) to cause an impression in letterpress printing. Platen may also refer to a typewriter roller which friction-feeds paper into position below the typebars or print head. It can refer to the glass surface of a copier, and the rotating disk used to polish semiconductor wafers.
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👉 Platen in the context of Letterpress
Letterpress printing is a technique of relief printing for producing many copies by repeated direct impression of an inked, raised surface against individual sheets of paper or a continuous roll of paper. A worker composes and locks movable type into the "bed" or "chase" of a press, inks it, and presses paper against it to transfer the ink from the type, which creates an impression on the paper.
In practice, letterpress also includes wood engravings; photo-etched zinc plates ("cuts"); linoleum blocks, which can be used alongside metal type; wood type in a single operation; 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. In theory, anything that is "type high" (i.e. it forms a layer exactly 0.918 inches thick between the bed and the paper) can be printed using letterpress.
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Platen in the context of Overhead projector
An overhead projector (often abbreviated to OHP), like a film or slide projector, uses light to project an enlarged image on a screen, allowing the view of a small document or picture to be shared with a large audience.
In the overhead projector, the source of the image is a page-sized sheet of transparent plastic film (also known as "viewfoils", "foils", "acetate" or "transparencies") with the image to be projected either printed or hand-written/drawn. These transparent sheets are placed on the glass platen of the projector, which has a light source below it and a projecting mirror and lens assembly above it (hence, "overhead"). They were widely used in education and business before the advent of video projectors.
Platen in the context of Sholes and Glidden typewriter
The Sholes and Glidden typewriter (also known as the Remington No. 1) was the first commercially successful typewriter. Principally designed by the American inventor Christopher Latham Sholes, it was developed with the assistance of fellow printer Samuel W. Soule and amateur mechanic Carlos S. Glidden. Work began in 1867, but Soule left the enterprise shortly thereafter, replaced by James Densmore, who provided financial backing and the driving force behind the machine's continued development. After several short-lived attempts to manufacture the device, the machine was acquired by E. Remington and Sons in early 1873. An arms manufacturer seeking to diversify, Remington further refined the typewriter before finally placing it on the market on July 1, 1874.
During its development, this typewriter evolved from a crude curiosity into a practical device, the basic form of which became the industry standard. The machine incorporated elements which became fundamental to typewriter design, including a cylindrical platen and a four row QWERTY keyboard. Several design deficiencies remained, however. The Sholes and Glidden could print only upper-case letters—an issue remedied in its successor, the Remington No. 2—and was a "blind writer", meaning the typist could not see what was being written as it was entered.