A spirit duplicator or ditto machine was a low-volume printing method used mainly by schools and churches. The technology fell into disuse with the availability of low cost, high volume xerographic copiers starting in the 1970s; few spirit duplicators remained in use by 1985.
Spirit duplicators were inexpensive and well suited to short runs. They owe most of their popularity to their relative ease of use. Even the least technically-minded teachers, professors, and clergy could make use of them.
Print quality was generally poor, though a capable operator could overcome this with careful adjustment of feed rate, pressure, and solvent volume.
Purple ink was used most often because it provided the best contrast.
Mimeograph machines predated the spirit duplicator, and had lower cost per impression and much better print quality. But mimeographs required handling of messy ink, and fell out of favor for casual 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 abominable but the machines were still popular because of their convenience.
From an article at http://www.deadmedia.org/notes/40/408.html written by dmorton@rci.rutgers.edu (David Morton):
The Spirit Duplicator
It was invented in 1923 by one Wilhelm Ritzerfeld, founder of the Ormig Company in Germany (Proudfoot 1972, 36). The spirit duplicator master consisted of a smooth paper master sheet and a "carbon" paper sheet (coated with a waxy compound similar to that used in the hectograph) acting "backwards" so that the wax compound (we'll call it the "ink") was transferred to the back side of the master sheet itself. The master could be typed or written on, and when finished the "carbon paper" was discarded. The master was wrapped around a drum in the spirit duplicator machine. As the drum turned, the master was coated with a thin layer of highly volatile duplicating fluid via a wick soaked in the fluid. The fluid acted to slightly dissolve or soften the "ink." As paper (preferably very smooth or coated) pressed against the drum and master copy, some of the "ink" was transferred to make the final copy. A spirit duplicator master was capable of making up to about 500 copies before the print became too faint to recognize.
The spirit duplicator was widely used in educational institutions for making all sorts of documents in small runs. Many students believed that inhaling the distinctive vapors given off by fresh spirit duplicator copies could provide a "high," a myth that (in my recollection) teachers did nothing to dispel.
One 1956 guide (Hermann, 1956, p. 208) lists several suppliers of spirit duplicators: Block, Anderson Ltd., Bohn Duplicator Corp., Copy-Craft, Inc., A B Dick Co., Ditto, Inc., S.p.A. Duplicatori ed Affini, Heyer Corp., Old Town Corp., Rex-O-Graph, Inc., S&M Distributing Co., Standard Duplicating Machines Corp., and Weber Marking Systems. Source(s):
M P Doss, Information Processing Equipment (New York, 1955) Irvin A. Herrmann, Manual of Office Reproduction (New York, 1956) W B Proudfoot, The Origin of Stencil Duplicating (London, 1972)
