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The stencil duplicator or mimeograph machine (often abbreviated to mimeo) is a low-cost printing press that works by forcing ink through a stencil onto paper. The mimeograph process should not be confused with the spirit duplicator process.
Mimeographs, along with spirit duplicators and hectographs, were a common technology in printing small quantities, as in office work, classroom materials, and church bulletins. Early fanzines were printed in this technology, because it was widespread and cheap. In the late 1960s, mimeographs, spirit duplicators, and hectographs were gradually displaced by photocopying and offset printing.
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Thomas Edison received US patent 180,857 for "Autographic Printing" on August 8, 1870. The patent covered the electric pen, used for making the stencil, and the flatbed duplicating press. In 1880 Edison obtained a further patent, US 224,665: "Method of Preparing Autographic Stencils for Printing", which covered the making of stencils using a file plate, a grooved metal plate on which the stencil was placed which perforated the stencil when written on with a blunt metal stylus.
Dick received Trademark Registration no. 0356815 for the term "Mimeograph" in the U.S. Patent Office. It is currently listed as a dead entry, but shows the A.B. Dick Company of Chicago as the owner of the name.
Over time, the term became generic and is now an example of a genericized trademark. ("Roneograph," also "Roneo machine," was another trademark used for mimeograph machines, the name being a contraction of Rotary Neostyle.)
Others who worked concurrently on the development of stencil duplicating were Eugenio de Zaccato and David Gestetner, both in Britain. In Britain the machines were most often referred to as "duplicators", though the predominance of Gestetner and Roneo in the UK market meant that some people referred to the machine by one of those two manufacturers' names.
In 1891, Gestetner patented his Automatic Cyclostyle. This was one of the first rotary machines that retained the flatbed, which passed back and forth under inked rollers. This invention provided for more automated, faster reproductions since the pages were produced and moved by rollers instead of pressing one single sheet at a time.
By 1900, two primary types of mimeographs had come into use: a single-drum machine and a dual-drum machine. The single-drum machine used a single drum for ink transfer to the stencil, and the dual-drum machine used two drums and silk-screens to transfer the ink to the stencils. The single drum (example Roneo) machine could be easily used for multi-color work by changing the drum - each of which contained ink of a different color. This was spot color for mastheads. Colors could not be mixed.
The mimeograph became popular because it was much cheaper than traditional print - there was no typesetting nor skilled labor involved. One individual with a typewriter and the necessary equipment essentially became his own printing factory, which allowed for greater circulation of printed material.
Mimeography process 
Once prepared, the stencil is wrapped around the ink-filled drum of the rotary machine. When a blank sheet of paper is drawn between the rotating drum and a pressure roller, ink is forced through the holes on the stencil onto the paper. Early flatbed machines used a kind of squeegee. The ink had a lanolin base.
Preparing stencils 
For printed copy, a stencil assemblage is placed in a typewriter. The typewriter ribbon has to be disabled so that the bare, sharp type element strikes the stencil directly. The impact of the type element displaces the wax, making the tissue paper permeable to the oil-based ink. This is called "cutting a stencil."
Mistakes can be corrected by brushing them out with a specially formulated correction fluid, and retyping once it has dried. ("Obliterine" was a popular brand of correction fluid in Australia and the United Kingdom.)
Stencils were also made with a thermal process, an infrared method similar to that used by early photocopiers. The common machine was called a Thermofax.
Another device, called an electrostencil machine, sometimes was used to make mimeo stencils from a typed or printed original. It worked by scanning the original on a rotating drum with a moving optical head and burning through the blank stencil with an electric spark in the places where the optical head detected ink. It was slow and filled the air with ozone and text produced from electrostencils was of lower resolution than that produced by typed stencils, although the process was good for reproducing illustrations. A skilled mimeo operator using an electrostencil and a very coarse halftone screen could make acceptable printed copies of a photograph.
Unlike spirit duplicators (where the only ink available is depleted from the master image), mimeograph technology works by forcing a replenishable supply of ink through the stencil master. In theory, the mimeograph process could be continued indefinitely, especially if a durable stencil master were used (e.g. a thin metal foil). In practice, most low-cost mimeo stencils gradually wear out over the course of producing several hundred copies. Typically the stencil deteriorates gradually, producing a characteristic degraded image quality until the stencil tears, abruptly ending the print run. If further copies are desired at this point, there is no choice but to make up another stencil from scratch.
Often, the stencil material covering the interiors of closed letterforms (e.g. "a", "b", "d", "e", "g", etc.) would fall away during continued printing, causing ink-filled letters in the resulting copies. The stencil would gradually stretch, starting near the top where the mechanical forces were greatest, causing a characteristic "mid-line sag" in the textual lines of the copies, that would progress until the stencil failed completely. The Gestetner Company (and others) devised various methods to make mimeo stencils last longer in use.
Compared to spirit duplication, mimeography produced a darker, more legible image. Spirit duplicated images were usually tinted a light purple or lavender. which gradually became lighter and fainter in color over the course of some dozens of copies. Mimeography was often considered "the next step up" in quality, capable of producing hundreds of copies. Print runs beyond that level were usually produced by professional printers, or as the technology became available, xerographic copiers.
Mimeographed images generally have much better durability than spirit duplicated images, since the inks are more resistant to ultraviolet light. The primary preservation challenge is the low-quality paper often used, which would yellow and degrade due to residual acid in the treated pulp from which the paper was made. In the worst case, old copies can literally crumble into small particles when handled. Mimeographed copies have moderate durability when acid-free paper is used.
Contemporary use 
Gestetner, Risograph, and other companies still make and sell highly automated mimeograph-like machines that are externally similar to photocopiers. The modern version of a mimeograph, called a digital duplicator, or copyprinter, contains a scanner, a thermal head for stencil cutting, and a large roll of stencil material entirely inside the unit. It makes the stencils and mounts and unmounts them from the print drum automatically, making it almost as easy to operate as a photocopier. The Risograph is the best known of these machines.
Although mimeographs remain more economical and energy-efficient in mid-range quantities, easier-to-use photocopying and offset printing have replaced mimeography almost entirely in developed countries. Mimeograph machines continue to be used in developing countries because it is a simple, cheap, and robust technology. Many mimeographs can be hand-cranked, and thus require no electricity.
Uses and art 
Mimeographs and the closely related but distinctly different spirit duplicator process were both used extensively in schools to copy homework assignments and tests. They were also commonly used for low-budget amateur publishing, including club newsletters and church bulletins. They were especially popular with science fiction fans, who used them extensively in the production of fanzines in the middle 20th century, before photocopying became inexpensive.
Letters and typographical symbols were sometimes used to create illustrations, in a precursor to ASCII art. Because changing ink color in a mimeograph could be a laborious process, involving extensively cleaning the machine or, on newer models, replacing the drum or rollers, and then running the paper through the machine a second time, some fanzine publishers experimented with techniques for painting several colors on the pad, notably Shelby Vick, who created a kind of plaid "Vicolor."
See also 
- Duplicating machines
- List of duplicating processes
- Spirit duplicator (also known as a "Ditto machine" in the U.S. or a "Banda machine" in the U.K.)
- mimeograph. The American Heritage Dictionary of the English Language: Fourth Edition. 2000
- Mimeograph Ink Vehicle Formula Chemical Industry
- "How to prepare a mimeograph stencil by using a typewriter". LinguaLinks Library. SIL International. Retrieved 2011-05-10.
- "How to prepare a mimeograph stencil by hand". LinguaLinks Library. SIL International. Retrieved 2011-05-10.
- "How to correct a mimeograph stencil". LinguaLinks Library. SIL International. Retrieved 2011-05-10.
- "How to prepare a mimeograph stencil by using a dot matrix printer". LinguaLinks Library. SIL International. Retrieved 2011-05-10.
- "Duplicating stencil". Patentstorm. Retrieved 2011-05-10.
- "Fancyclopedia: Vicolor". Fancyclopedia.wikidot.com. Retrieved 2009-10-14.
Further reading 
- Hutchison, Howard. Mimeograph: Operation Maintenance and Repair. Blue Ridge Summit: Tab Books, 1979.
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