Editing Duplicating machines (section)

==Spirit duplicators==

{{main|Spirit duplicator}}
The [[spirit duplicator]] invented in 1923 and sold by Ditto, Inc., used two-ply "spirit masters" or "ditto masters".  The top sheet could be typed, drawn, or written upon.{{Citation needed|date=March 2009}} The second sheet was coated with a layer of colored wax. 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 wax-supply sheet was then removed and discarded, and the other sheet (containing the images) was fastened onto the drum of the (manual or electrical) machine, with the waxed (back, or reverse-image) side out.

The usual wax color was [[aniline]] purple, a cheap, moderately durable pigment that provided good contrast, though other colors were also available. Unlike mimeo, ditto had the useful ability to print multiple colors in a single pass, which made it popular with cartoonists. Spirit duplicators were incapable of double-sided printing, since the saturation of the paper with solvent inherent to the process would destroy a previously printed image. One well-made spirit master could at most print about 500 copies, far fewer than a mimeograph stencil could manage. To produce further copies, an entirely new master would have to be reconstructed in the same way as the original master.

Notoriously, images would gradually fade with exposure to light{{Citation needed|date=March 2009}}, limiting their usability for permanent labels and signage. Copies made by spirit duplicators now pose a serious challenge to [[archivist]]s responsible for document textual and artistic preservation.