The earliest widely used copy machine for offices was invented by James Watt in 1779. It relied on physically transferring some of the (specially formulated) ink from an original letter or drawing to a moistened thin unsized sheet of paper by way of a press. The copy could then be read from the opposite side. The system was a business success and was in use in for over a century.
In 1937, Bulgarian physicist Georgi Nadjakov found that, when placed into an electric field and exposed to light, some dielectrics acquire permanent electric polarization in the exposed places. That polarization persists in the dark and is eradicated in light.
Chester Carlson, the creator of photocopying, was originally a patent attorney, as well as a part-time researcher and inventor. His job at the patent office in New York needed him to make a large number of copies of important papers. Carlson, who was arthritic, found this to be a painful and wearisome process. This inspired him to conduct experiments with photoconductivity. Carlson used his kitchen for his "electrophotography" experiments, and, in 1938, he applied for a patent for the system. He made the earliest photocopy using a zinc plate covered with sulfur. The words "10-22-38 Astoria" were written on a microscope slide, which was placed on top of more sulfur and below a bright light. After the slide was taken out, a mirror image of the words remained. Carlson tried to sell his creation to some companies, but failed because the process was still underdeveloped. At the time, multiple copies were most commonly made at the point of document origination, implementing carbon paper or manual duplicating machines, and people did not see the need for an electronic machine. Between 1939 and 1944, Carlson was turned down by over 20 companies, including IBM and General Electric—neither of which believed there was a large market for copiers.
In 1944, the Battelle Memorial Institute, a non-profit organization in Columbus, Ohio, contracted with Carlson to refine his new system. Over the next five years, the institute conducted experiments to improve the system of electrophotography. In 1947, Haloid Corporation (a small New York-based manufacturer and seller of photographic paper) approached Battelle to obtain a license to create and market a copying machine based on this technology.
Haloid felt that the word "electrophotography" was too complicated and did not have good remembrance value. After consulting a professor of classical language at Ohio State University, Haloid and Carlson modified the name of the process to "xerography," which was derived from Greek words that meant "dry writing." Haloid called the new copier machines "Xerox Machines" and, in 1948, the phrase "Xerox" was trademarked. Haloid eventually reformed its name to Xerox Corporation.
In 1949, Xerox Corporation introduced the earliest xerographic copier called the Model A. Xerox became so successful that, in North America, photocopying came to be highly known as "xeroxing." Xerox has actively fought to prevent "Xerox" from turning into a generalized trademark. While the word "Xerox" has appeared in some dictionaries as a synonym for photocopying, Xerox Corporation typically requests that such entries be changed, and that people not use the term "Xerox" in this way. Some languages include hybrid terms, such as the widely used Polish term kserokopia ("xerocopy"), even though relatively small amount of photocopiers are of the Xerox brand.
In the early 1950s, Radio Corporation of America (RCA) introduced a variation on the process called Electrofax, whereby images are formed directly on specially coated paper and rendered with a toner distributed in a liquid.
During the 1960s and through the 1980s, Savin Corporation created and sold a line of liquid-toner copiers that implemented a technology based on patents held by the company.
Prior to the widespread adoption of xerographic copiers, photo-direct copies made by machines such as Kodak's Verifax were implemented. A primary obstacle associated with the pre-xerographic copying technologies was the high cost of supplies: a Verifax print required supplies costing USD $0.15 in 1969, while a Xerox print could be done for USD $0.03 including paper and labor. At that time, Thermofax photocopying machines in libraries could make letter-sized copies for USD $0.25 or larger (at a time when the minimum wage for a US worker was USD $1.65/hour).
Xerographic copier constructers took advantage of a high perceived-value of the 1960s and early 1970s, and marketed paper that was "specially designed" for xerographic output. By the end of the 1970s, paper makers made xerographic "runability" one of the requirements for most of their office paper brands.
Some machines sold as photocopiers have replaced the drum-based process with inkjet or transfer film technology.
Among the key advantages of photocopiers over the oldest copying technologies is their ability:
• to implement regular (untreated) office paper
• to use duplex (or two-sided) printing, and
• in time, to sort and/or staple output.
Colored toner became ready in the 1950s, although full-color copiers were not commercially available until 3M released the Color-in-Color copier in 1968, which used a dye sublimation process rather than conventional electrostatic technology. The earliest electrostatic color copier was released by Canon in 1973.
Color photocopying is a burden to governments, as it facilitates counterfeiting currency. Some countries have made anti-counterfeiting technologies into their currency specifically to make it harder to use a color photocopier for counterfeiting. These technologies include watermarks, microprinting, holograms, tiny security strips constructed of plastic (or other material), and ink that appears to change color as the currency is viewed at an angle. Some photocopying machines have special software that can prevent copying currency that contains a special pattern.
There is an raising trend for new photocopiers to adopt digital technology, thus replacing the older analog technology. With digital copying, the copier effectively consists of a mix scanner and laser printer. This design has several advantages, such as automatic image quality improvement and the ability to "build jobs" (that is, to scan page images independently of the process of printing them). Some digital copiers can work as high-speed scanners; such models typically offer the ability to send documents via email or to make them available on file servers.
A great plus of digital copier technology is "automatic digital collation." For example, when copying a set of 20 pages 20 times, a digital copier scans every page only once, and then uses the stored information to produce 20 sets. In an analog copier, either each page is scanned 20 times (a total of 400 scans), making one set at a time, or 20 separate output trays are implemented for the 20 sets.
Low-end copiers also implement digital technology, but tend to consist of a standard PC scanner coupled to an inkjet or low-end laser printer, both of which are far slower than their counterparts in high-end copiers. However, low-end scanner-inkjets can make use color copying at a far lower cost than can a traditional color copier. The value of electronics is such that combined scanner-printers sometimes have built-in fax machines.