Xerography (Inventions)

The invention: Process that makes identical copies of documents with a system of lenses, mirrors, electricity, chemicals that conduct electricity in bright light, and dry inks (toners) that fuse to paper by means of heat.

The people behind the invention:

Chester F. Carlson (1906-1968), an American inventor Otto Kornei (1903- ), a German physicist and engineer
Xerography, Xerography, Everywhere
The term xerography is derived from the Greek for “dry writing.” The process of xerography was invented by an American, Chester F. Carlson, who made the first xerographic copy of a document in 1938. Before the development of xerography, the preparation of copies of documents was often difficult and tedious. Most often, unclear carbon copies of typed documents were the only available medium of information transfer.
The development of xerography led to the birth of the giant Xerox Corporation, and the term xerographic was soon shortened to Xerox. The process of xerography makes identical copies of a document by using lens systems, mirrors, electricity, chemicals that conduct electricity in bright light (“semiconductors”), and dry inks called “toners” that are fused to copy paper by means of heat. The process makes it easy to produce identical copies of a document quickly and cheaply. In addition, xerography has led to huge advances in information transfer, the increased use of written documents, and rapid decision-making in all areas of society. Xeroxing can produce both color and black-and-white copies.

From the First Xerox Copy to Modern Photocopies

On October 22,1938, after years of effort, Chester F. Carlson produced the first Xerox copy. Reportedly, his efforts grew out of his 1930′s job in the patent department of the New York firm P. R.
Mallory and Company. He was looking for a quick, inexpensive method for making copies of patent diagrams and other patent specifications. Much of Carlson’s original work was conducted in the kitchen of his New York City apartment or in a room behind a beauty parlor in Astoria, Long Island. It was in Astoria that Carlson, with the help of Otto Kornei, produced the first Xerox copy (of the inscription “10-22-38 Astoria”) on waxed paper.
The first practical method of xerography used the element selenium, a substance that conducts electricity only when it is exposed to light. The prototype Xerox copying machines were developed as a result of the often frustrating, nerve-wracking, fifteen-year collaboration of Carlson, scientists and engineers at the Battelle Memorial Institute in Columbus, Ohio, and the Haloid Company of Rochester, New York. The Haloid Company financed the effort after 1947, based on an evaluation made by an executive, John H. Dessauer. In return, the company obtained the right to manufacture and market Xerox machines. The company, which was originally a manufacturer of photographic paper, evolved into the giant Xerox Corporation. Carlson became very wealthy as a result of the royalties and dividends paid to him by the company.
Early xerographic machines operated in several stages. First, the document to be copied was positioned above a mirror so that its image, lit by a flash lamp and projected by a lens, was reflected onto a drum coated with electrically charged selenium. Wherever dark sections of the document’s image were reflected, the selenium coating retained its positive charge. Where the image was light, the charge of the selenium was lost, because of the photoactive properties of the selenium.
Next, the drum was dusted with a thin layer of a negatively charged black powder called a “toner.” Toner particles stuck to positively charged dark areas of the drum and produced a visible image on the drum. Then, Xerox copy paper, itself positively charged, was put in contact with the drum, where it picked up negatively charged toner. Finally, an infrared lamp heated the paper and the toner, fusing the toner to the paper and completing the copying process.
In ensuing years, the Xerox Corporation engineered many changes in the materials and mechanics of Xerox copiers. For example, the semiconductors and toners were changed, which increased both the

Chester F. Carlson

The copying machine changed Chester Floyd Carlson’s life even before he invented it. While he was experimenting with photochemicals in his apartment, the building owner’s daughter came by to complain about the stench Carlson was creating. However, she found Carlson himself more compelling than her complaints and married him not long afterward. Soon Carlson transferred his laboratory to a room behind his mother-in-law’s beauty parlor, where he devoted ten dollars a month from his meager wages to spend on research.
Born in Seattle, Washington, in 1906, Carlson learned early to husband his resources, set his goals high, and never give up. Both his father and mother were sickly, and so after he was fourteen, Carlson was the family’s main breadwinner. His relentless drive and native intelligence got him through high school and into a community college, where an impressed teacher inspired him to go even further—into the California Institute of Technology. After he graduated, he worked for General Electric but lost his job during the layoffs caused by the Great Depression. In 1933 he hired on with P. R. Mallory Company, an electrical component manufacturer, which, although not interested in his invention, at least paid him enough in wages to keep going.
His thirteen-year crusade to invent a copier and then find a manufacturer to build it ended just as Carlson was nearly broke. In 1946 Haloid Corporation licensed the rights to Carlson’s copying machine, but even then the invention did not become an important part of American communications culture until the company marketed the Xerox 914 in 1960. The earnings for Xerox Corporation (as it was called after 1961) leapt from $33 million to more than $500 million in the next six years, and Carlson became enormously wealthy. He won the Inventor of the Year Award in 1964 and the Horatio Alger Award in 1966. Before he died in 1968, he remembered the hardships of his youth by donating $100 million to research organizations and charitable foundations.
quality of copies and the safety of the copying process. In addition, auxiliary lenses of varying focal length were added, along with other features, which made it possible to produce enlarged or reduced copies. Furthermore, modification of the mechanical and chemical properties of the components of the system made it possible to produce thousands of copies per hour, sort them, and staple them.
The next development was color Xerox copying. Color systems use the same process steps that the black-and-white systems use, but the document exposure and toning operations are repeated three times to yield the three overlaid colored layers (yellow, magenta, and cyan) that are used to produce multicolored images in any color printing process. To accomplish this, blue, green, and red filters are rotated in front of the copier’s lens system. This action produces three different semiconductor images on three separate rollers. Next, yellow, magenta, and cyan toners are used—each on its own roller—to yield three images. Finally, all three images are transferred to one sheet of paper, which is heated to produce the multicolored copy. The complex color procedure is slower and much more expensive than the black-and-white process.


The quick, inexpensive copying of documents is commonly performed worldwide. Memoranda that must be distributed to hundreds of business employees can now be copied in moments, whereas in the past such a process might have occupied typists for days and cost hundreds of dollars. Xerox copying also has the advantage that each copy is an exact replica of the original; no new errors can be introduced, as was the case when documents had to be retyped. Xerographic techniques are also used to reproduce X rays and many other types of medical and scientific data, and the facsimile (fax) machines that are now used to send documents from one place to another over telephone lines are a variation of the Xerox process.
All this convenience is not without some problems: The ease of photocopying has made it possible to reproduce copyrighted publications. Few students at libraries, for example, think twice about copying portions of topics, since it is easy and inexpensive to do so. However, doing so can be similar to stealing, according to the law. With the advent of color photocopying, an even more alarming problem has arisen: Thieves are now able to use this technology to create counterfeit money and checks. Researchers will soon find a way to make such important documents impossible to copy.
See also Fax machine; Instant photography; Laser-diode recording process.

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