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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.

The term "spirit duplicator" comes from the alternative term for alcohols, which is "spirits." Alcohols were a major component of the solvents used as "inks" in these machines.

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.

Contents 1 Mechanism of use 1.1 Colours 1.2 Paper 1.3 Thermofax 2 Toxic substances 2.1 Smell 3 Decline in use 4 See also 5 References 6 External links

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 moved through the printer, the solvent would be spread across each sheet by an absorbent wick. When the solvent-impregnated paper came into contact with the waxed original, it would dissolve just enough of the pigmented wax to print the image onto the sheet as it went under the printing drum.

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.

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 unreadably faint. If fewer copies were required, the master could be removed from the printing drum and saved for future use.

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.

Both the isopropanol and the methanol found in ditto solvents are toxic substances. These chemicals can cause a host of medical problems when humans are improperly exposed. Material Safety Data Sheet (MSDS) guidelines recommend the use of personal protective equipment during exposure to methanol,^{[citation needed]} however, most^{[attribution needed]} chemists work with methanol and isopropanol wearing only medical exam grade gloves, goggles and a working fume hood as the chief, no-ingested or inhaled reaction with methanol is limited skin irritation.^{[citation needed]}

Despite their toxicity, 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.

Spirit duplicator technology fell into disuse sometime after the availability of low-cost, high-volume xerographic copiers starting in the 1970s.^{[citation needed]} They remained popular through the early 1990s in applications such as events where no electrical power was available.^{[citation needed]} The technology was also used until then by science fiction fandom for the production of fanzines, particularly for amateur press associations.

• Duplicating machines
• List of duplicating processes

• The Dead Media Project
• M P Doss, Information Processing Equipment (New York, 1955)
• Irvin A. Herrmann, Manual of Office Reproduction (New York, 1956)

• "Duplicating in the year B.C. - Before (xerographic) Copies"