Spark printing is an obsolete form of computer printing and before that fax and chart recorder printing which uses a special paper coated with a conductive layer over a contrasting backing, originally black carbon over white paper but later aluminium over black paper. Printing on this paper uses pulses of electric current to burn away spots of the conductive layer. Typically, one or more electrodes are swept across the page perpendicular to the direction of paper motion to form a raster of potential burnt spots.
|Part of a series on the|
|History of printing|
Western Union developed the paper for this printing technology in the late 1940s, under the trademark "Teledeltos". The Western Union "Deskfax" fax machine, announced in 1948, was one of the first printers to use this technology.
Spark printing was a simple and inexpensive technology. The print quality was relatively poor, but at a time when conventional printers cost hundreds of pounds, spark printers' sub-£100 price was a major selling point. The other major downside is that they can only print onto special metallised paper. Such electrosensitive paper is no longer widely available, but is still sold as of 2020.