Spark printer

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The Sinclair ZX Printer was a small spark printer for the ZX81 and ZX Spectrum computers.

A spark printer uses a special paper coated with a layer of aluminium over a black backing, which is printed on by using a pulsing current onto the paper via two styli that move across on a moving belt at high speed. It was a simple and inexpensive technology which produced fairly good results. At a time when conventional printers cost hundreds of dollars, the sub-$100 price of that type of printer was a major selling point. The only major downside is that it can only print onto the special metallised paper which it uses; unfortunately that paper is no longer readily available.

The technology was sometimes misleadingly referred to as a "thermal printer."

The Sinclair ZX printer, introduced in November 1981, for the ZX81 and ZX Spectrum computers, used the same spark and aluminised paper printing method, and retailed for £49.95.

In the early 1980s, Casio released a "Mini Electro Printer", the FP-10^[1] for some of their scientific calculators.

Another implementation of the spark printer was to propel dry toner from a tiny hole in the end of a glass rod, using a high-voltage spark between the platen and print head. The glass toner rod held a solid mass of toner, pushed toward the ejection tip by a spring. This had the advantage of printing onto plain paper, but the disadvantage of the toner not being cured to the paper, and thus easily smudged. Unlike the sinclair printer, this printer had only one stylus (the toner rod), since the entire platen behind the paper served as the other spark electrode. The printer could only print one line of pixels at a time.