Spark printing is an obsolete form of computer printing and before that fax and chart recorder printing which uses a special

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...

coated with a conductive layer over a contrasting backing, originally black carbon over white paper but later

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

over black paper. Printing on this paper uses

pulse In medicine, the pulse refers to the rhythmic pulsations (expansion and contraction) of an artery in response to the cardiac cycle (heartbeat). The pulse may be felt ( palpated) in any place that allows an artery to be compressed near the surfac ...

s of

electric current An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...

to burn away spots of the conductive layer. Typically, one or more

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...

s are swept across the page perpendicular to the direction of paper motion to form a raster of potential burnt spots.

Western Union The Western Union Company is an American multinational financial services corporation headquartered in Denver, Denver, Colorado. Founded in 1851 as the New York and Mississippi Valley Printing Telegraph Company in Rochester, New York, the co ...

developed the paper for this printing technology in the late 1940s, under the trademark " Teledeltos". The Western Union "Deskfax"

fax machine Fax (short for facsimile), sometimes called telecopying or telefax (short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other out ...

, 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 and such an electrosensitive paper is no longer widely available, but is still sold as of 2020.

Models

By 1979, the Comprint 912 was widely advertised as being faster, quieter, and less expensive than competitive matrix printers, with its "special aluminized 'silver paper'" being superior to ordinary paper, and "on those rare occasions when you really do need a plain bond paper copy, just run your Comprint 912 printout through your plain bond copy machine and you've got it." The Sinclair ZX Printer, introduced in November 1981 for the low-end

ZX81 The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-c ...

(and later for the

ZX Spectrum The ZX Spectrum () is an 8-bit computing, 8-bit home computer developed and marketed by Sinclair Research. One of the most influential computers ever made and one of the all-time bestselling British computers, over five million units were sold. ...

)

home computer Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a s ...

s used the spark printing method, and retailed for . In the early 1980s,

Casio is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It ...

released a "Mini Electro Printer", the FP-10 for some of their

scientific calculator A scientific calculator is an Electronics, electronic calculator, either desktop or handheld, designed to perform calculations using basic (addition, subtraction, multiplication, Division (mathematics), division) and advanced (Trigonometric fun ...

s. It used Casio CMP-36x5 paper. The Hewlett Packard 9120A, which attached to the top of the HP-9100A/B calculator, also used the sparking technique. Tandy / Radio Shack TRS-80 Screen Printer, Quick Printer, and Quick Printer II all used this same method and special paper. The

Sharp Corporation is a Japanese electronics company. It is headquartered in Sakai, Osaka, and was founded by Tokuji Hayakawa in 1912 in Honjo, Tokyo, and established as the Hayakawa Metal Works Institute in Abeno-ku, Osaka, in 1924. Since 2016, it is majority o ...

ELSIMATE EL-8151 portable calculator had a built in spark printer which used silver-colored paper. It is known to be compatible with the Casio CMP-36x5 paper used by the FP-10, despite the Casio paper having a slightly larger core diameter.

Variants

A different spark printer implementation propelled 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. Similar to the Sinclair printer, this printer had only one stylus (the toner rod), since the entire plate behind the paper served as the other spark electrode. The printer could only print one line of pixels at a time.

References

{{reflist Non-impact printing Printing technology