APS News

This Month in Physics History

October 22, 1938: "Invention of Xerography"

xerography

xerography
Sometimes it takes extraordinary patience, perseverance, and belief in oneself before the usefulness of an invention is finally realized. Take the case of physicist Chester Carlson, who invented the xerographic process, thereby launching what is today a multi-billion dollar industry. But for several years after patenting his process, Carlson could find no company interested in xerography. It was the invention that nobody wanted.

He developed much of his patience and perseverance during an especially difficult childhood. Born in Seattle, WA, in 1906, Carlson was the only child of an itinerant barber and grew up in southern California. By age 14 he was working after school and weekends for a local printer to support the family, since his father was crippled from arthritis. His mother succumbed to tuberculosis when he was 17. Always fascinated by graphic arts and chemistry, Carlson didn't let his humble roots deter him from finishing high school and working his way through a nearby junior college, earning a degree in chemistry. He then attended Caltech, graduating two years later with a degree in physics.

Unfortunately, Carlson entered the job market in the midst of the Depression, applying to 82 firms before landing a job as a research engineer at Bell Telephone Laboratories in New York City. His success was short lived and he was soon laid off because of the deepening Depression, finally securing a position with an electronics firm, P.R. Mallory & Co. He studied law at night at the New York Law School, and eventually became manager of the company's patent department. Despite the security of a steady job in uncertain times, Carlson was dissatisfied and restless, and devoted his leisure hours to the pursuit of invention.

Around this time, he noticed that there never seemed to be enough copies of patent specifications around the office, and no quick or practical means of obtaining more copies. There were only two options: either send the patents out to be photographed, or laboriously type new ones, both of which were costly and time consuming. Carlson conceived of a device that would accept a document and make copies of it in seconds, researched various imaging processes at the New York Public Library, and eventually lit on the then little-known field of photoconductivity, specifically the research of Hungarian physicist Paul Selenyi. Carlson combined two fundamental concepts: materials with opposite electrical charges attract one another, and some materials conduct electricity better after being exposed to light.

Carlson began conducting experiments in the kitchen of his apartment in Queens, eventually developing the fundamental principles of what he called "electrophotography", later known as xerography. His theory was that if the image of an original photograph or document were projected onto a photoconductive surface, current would only flow in the areas that light hit upon, and not in the areas of darkness, i.e., the print. If he could get dry particles to stick to a charged plate in a pattern corresponding to an image shining on the plate, he could make "dry reproduction" work. After filing a patent application in October 1937, he set up a small lab in Astoria and hired a lab assistant, a German refugee named Otto Kornei.

It was there that the first xerographic copy was made on October 22, 1938. The two men prepared a sulfur coating on a zinc plate, and Kornei printed a notation in India ink on a glass microscopic slide: "10- 22-38 Astoria." They pulled down the shade to darken the room, then rubbed the sulfur surface vigorously with a handkerchief to apply an electrostatic charge. The slide was laid on the surface, and the two pieces were placed under a bright incandescent lamp for a few seconds. The slide was then removed and lycopodium powder was sprinkled on the sulfur surface, then blown off. What was left on the surface was a near-perfect duplicate in powder of the same notation on the glass slide. After repeating the experiment several times to reassure themselves the process worked, the men made permanent copies by transferring the powder images to wax paper and heating the sheets to melt the wax.

Carlson shopped his invention around for several years trying to find a company to develop it into a useful product, and was turned down by more than 20 companies, as well as the National Inventors Council. "How difficult it was to convince anyone that my tiny plates and rough image held the key to a tremendous new industry," Carlson later recalled. Finally, in 1944, Battelle Memorial Institute, a nonprofit research organization, signed a royalty agreement with Carlson and began to develop the process. Three years later, Battelle made an agreement with a small photo paper company called Haloid (later to be known as Xerox), giving Haloid the right to develop a xerographic machine.

Twenty-one years after Carlson made the first xerographic copy in his modest Queens laboratory, the first office copier was unveiled in 1959. The Xerox 914 copier could make copies quickly at the touch of a button on plain paper, and was a phenomenal success.

Today, xerography is the foundation stone of the worldwide copying industry, and Carlson ended his years as a wealthy and much-honored man. But he remained both humble and generous, giving away $100 million of his personal fortune to charity before his death.


©1995 - 2016, AMERICAN PHYSICAL SOCIETY
APS encourages the redistribution of the materials included in this newspaper provided that attribution to the source is noted and the materials are not truncated or changed.

Editor: Alan Chodos
Associate Editor: Jennifer Ouellette