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A spirit duplicator (also referred to as a Ditto machine or Banda machine) was a low-volume printing method used mainly by schools and churches. Sheets printed on a ditto machine were called ditto sheets, or just dittos. The term "spirit duplicator" refers to the alcohols which were a major component of the solvents used as "inks" in these machines. They are sometimes confused with the mimeograph, which is actually a different technology.
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History
The spirit duplicator was invented in 1923 by Wilhelm Ritzerfeld. The best-known manufacturer in the United States was Ditto Corporation of Illinois, hence that name.
The thermofax machine was introduced by 3M in the late 1960s and could make a spirit master from an ordinary typewritten or handwritten sheet. The resulting print quality was very poor but the machines were popular because of their convenience.
Spirit duplicator technology gradually fell into disuse starting in the 1970s after the availability of low-cost, high-volume xerographic copiers; by the mid 1990s, the use of the technology was rare. The technology remains useful where electrical power is unavailable or where the only remaining originals of legacy documents requiring duplication are in "spirit master" form.
Operation
The duplicator used two-ply "spirit masters" or "ditto masters". The first sheet could be typed, drawn, or written upon. The second sheet was coated with a layer of wax that had been impregnated with one of a variety of colorants. The pressure of writing or typing on the top sheet transferred colored wax to its back side, producing a mirror image of the desired marks. (This acted like a reverse of carbon paper.) The two sheets were then separated, and the first sheet was fastened onto the drum of the (manual or electrical) machine, with the waxed side out.
There is no ink used in spirit duplication. As the paper moves through the printer, the solvent is spread across each sheet by an absorbent wick. When the solvent-impregnated paper comes into contact with the waxed original, it dissolves just enough of the pigmented wax to print the image onto the sheet as it goes under the printing drum.
Colors
The usual wax color was aniline purple, a cheap, durable pigment that provided good contrast, but ditto masters were also manufactured in red, green, blue, black, and the hard-to-find orange, yellow, and brown. All except black reproduced in pastel shades: pink, mint, sky blue, etc. Ditto had the useful ability to print multiple colors in a single pass, which made it popular with cartoonists. Multi-colored designs could be made by swapping out the waxed second sheets; for instance, shading in only the red portion of an illustration while the top sheet was positioned over a red-waxed second sheet. This was possible because the pungent-smelling duplicating fluid (typically a 50/50 mix of isopropanol and methanol) was not ink, but a clear solvent.
Paper
This process worked best with cheap, lightweight paper stocks, but when the sheets of paper were impregnated with the solvent they could easily crease or crumple, jamming the machine. One well-made ditto master could at most print about 500 copies before the pigment was exhausted and the print quality became illegibly faint. If fewer copies were required, the master could be removed from the printing drum and saved for future use.
Smell
The aroma of pages fresh off the Ditto machine was a memorable feature of school life for those who attended in the ditto machine era. A pop culture reference to this is to be found in the film Fast Times At Ridgemont High. At one point a teacher hands out a dittoed exam paper and every student in the class immediately lifts it to his or her nose and inhales.
See also
Further reading
- Dead medium: Spirit Duplicators at The Dead Media Project
- M P Doss, Information Processing Equipment (New York, 1955)
- Irvin A. Herrmann, Manual of Office Reproduction (New York, 1956)
External links
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