Edited by Gerald Boerner



Due to injury, this commentary will be added later. Please check back. Thank you.  GLB

These Introductory Comments are copyrighted:
Copyright©2010 — Gerald Boerner — All Rights Reserved

[ 3851 Words ]


Quotations Related to XEROX

“Once the Xerox copier was invented, diplomacy died.”
— Andrew Young

“I thought administration was the running of the office. The Xerox machine. Paying bills.”
— Lesley Stahl

“It’s good Xerox is known for its copying machines, and it’s good Jim Carrey is known for comedy.”
— Steve Guttenburg

“A journalistic purpose could be someone with a Xerox machine in a basement.”
— Antonin Scalia

“A free America… means just this: individual freedom for all, rich or poor, or else this system of government we call democracy is only an expedient to enslave man to the machine and make him like it.”
— Frank Lloyd Wright

“A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts.”
— William Strunk, Jr.

“A tool is usually more simple than a machine; it is generally used with the hand, whilst a machine is frequently moved by animal or steam power.”
— Charles Babbage

“Xerox did OK in moving to digital in the commercial space. They didn’t do well in the consumer market, but they’re not a consumer brand. They don’t even know how to spell consumer.”
— Antonio Perez


Chester Carlson — Roots of Xerographic Photocopying Process

Chester-carlson-stamp Chester Floyd Carlson (1906 – 1968) was an American physicist, inventor, and patent attorney born in Seattle, Washington.

He is best known for having invented the process of electrophotography, which produced a dry copy rather than a wet copy, as was produced by the mimeograph process. Carlson’s process was subsequently renamed to xerography, a term that literally means "dry writing."

Carlson began thinking about reproducing print early in his life. At age ten, he created a newspaper called This and That, created by hand and circulated among his friends with a routing list. His favorite plaything was a rubber stamp printing set, and his most coveted possession was a toy typewriter an aunt gave him for Christmas in 1916—although he was disappointed that it wasn’t an office typewriter.

While working for a local printer while in high school, Carlson attempted to typeset and publish a magazine for science-minded students like himself. He quickly became frustrated with traditional duplicating techniques. As he told Dartmouth College professor Joseph J. Ermene in a 1965 interview, "That set me to thinking about easier ways to do that, and I got to thinking about duplicating methods."


“Well, I had a fascination with the graphic arts from childhood. One of the first things I wanted was a typewriter—even when I was in grammar school. Then, when I was in high school I liked chemistry and I got the idea of publishing a little magazine for amateur chemists. I also worked for a printer in my spare time and he sold me an old printing press which he had discarded. I paid for it by working for him. Then I started out to set my own type and print this little paper. I don’t think I printed more than two issues, and they weren’t much. However, this experience did impress me with the difficulty of getting words into hard copy and this, in turn, started me thinking about duplicating processes. I started a little inventor’s notebook and I would jot down ideas from time to time.”
—Chester Carlson, to A. Dinsdale, when asked about his choice of field

Because of the work he put in supporting his family, Carlson had to take a postgraduate year at his high school to fill in missed courses. He then entered a cooperative work/study program at Riverside Junior College, working and going to classes in alternating six-week periods. Carlson held three jobs while at Riverside, paying for a cheap one-bedroom apartment for himself and his father. At Riverside, Chester began as a chemistry major, but switched to physics, largely due to a favorite professor.

After three years at Riverside, Chester transferred to the California Institute of Technology, or Caltech—his ambition since high school. His tuition, $260 a year, exceeded his total earnings, and the workload prevented him from earning much money—though he did mow lawns and do odd jobs on weekends, and work at a cement factory in the summer. By the time he graduated, he was $1,500 in debt. He graduated with good—but not exceptional—grades, earning a B.S. degree in Physics in 1930, near the start of the Great Depression. He wrote letters seeking employment to 82 companies; none offered him a job.

Early Career

“The need for a quick, satisfactory copying machine that could be used right in the office seemed very apparent to me—there seemed such a crying need for it—such a desirable thing if it could be obtained. So I set out to think of how one could be made.”
—Chester Carlson

As a last resort, he began working for Bell Telephone Laboratories in New York City as a research engineer. Finding the work dull and routine, After a year, Carlson transferred to the patent department as an assistant to one of the company’s patent attorneys.

Carlson wrote over 400 ideas for new inventions in his personal notebooks while working at Bell Labs. He kept coming back to his love of printing, especially since his job in the patent department gave him new determination to find a better way to copy documents. "In the course of my patent work," wrote Carlson, "I frequently had need for copies of patent specifications and drawings, and there was no really convenient way of getting them at that time." At the time, the department primarily made copies by having typists retype the patent application in its entirety, using carbon paper to make multiple copies at once. There were other methods available, such as mimeographs and Photostats, but they were more expensive than carbon paper, and they had other limitations that made them impractical. The existing solutions were ‘duplicating’ machines—they could make many duplicates, but one had to create a special master copy first, usually at great expense of time or money. Carlson wanted to invent a ‘copying’ machine, that could take an existing document and copy it onto a new piece of paper without any intermediate steps.

In 1933, during the Great Depression, Carlson was fired from Bell Labs for participating in a failed "business scheme" outside of the Labs with several other employees. After six weeks of job-hunting, he got a job at the firm Austin & Dix, near Wall Street, but he left the job about a year later as the firm’s business was declining. He got a better job at the electronics firm P. R. Mallory Company, founded by Philip Mallory (now known as the Duracell division of Procter & Gamble), where Carlson was promoted to head of the patent department.

The Invention of Electrophotography

“There was a gap of some years, but by 1935 I was more or less settled. I had my job, but I didn’t think I was getting ahead very fast. I was just living from hand to mouth, you might say, and I had just got married. It was kind of a hard struggle. So I thought the possibility of making an invention might kill two birds with one stone; it would be a chance to do the world some good and also a chance to do myself some good.”
— Chester Carlson, to A. Dinsdale

In 1936, Carlson began to study law at night at New York Law School, receiving his LL.B. degree in 1939. He studied at the New York Public Library, copying longhand from law books there because he couldn’t afford to buy them. The pains induced by this laborious copying hardened his resolve to find a way to build a true copying machine. He began supplementing his law studies with trips to the Public Library’s science and technology department. It was there that he was inspired by a brief article, written by Hungarian physicist Pál Selényi in an obscure German scientific journal, that showed him a way to obtain his dream machine.

Carlson’s early experiments, conducted in his apartment kitchen, were smoky, smelly, and occasionally explosive. In one set of experiments, he was melting pure crystalline sulfur (a photoconductor) onto a plate of zinc by moving it just so over the flame of his kitchen stove. This often resulted in a sulfur fire, filling the building with the smell of rotten eggs. In another experiment, the chemicals he was working with caught fire, and he and his wife were hard-pressed to extinguish the flames.

During this period, he developed arthritis of the spine, like his father. He pressed on with his experiments, however, in addition to his law school studies and his regular job.

Having learned about the value of patents in his early career as a patent clerk and attorney, Carlson patented his developments every step along the way. He filed his first preliminary patent application on October 18, 1937.

By the fall of 1938, Carlson’s wife had convinced him that his experiments needed to be conducted elsewhere. He rented a room on the second floor of a house owned by his mother-in-law at 32-05 37th Street in Astoria, Queens. He hired an assistant, Otto Kornei, an out-of-work Austrian physicist.

Carlson knew that several major corporations were researching ways of copying paper. The Haloid Company had the Photostat, which it licensed to Eastman Kodak, the photography giant. However, these companies were researching along photographic lines, and their solutions required special chemicals and papers. The Photostat, for instance, was essentially a photograph of the document being copied.


Selényi’s article described a way of transmitting and printing facsimilies of printed images using a beam of directed ions directed onto a rotating drum of insulating material. The ions would create an electrostatic charge on the drum. A fine powder could then be dusted upon the drum; the powder would stick to the parts of the drum that had been charged, much as a balloon will stick to a static-charged stocking.

To this point, Carlson’s apartment-kitchen experiments in constructing a copying machine had involved trying to generate an electric current in the original piece of paper using light. Selényi’s article convinced Carlson to instead use light to ‘remove’ the static charge from a uniformly-ionized photoconductor. As no light would reflect from the black marks on the paper, those areas would remain charged on the photoconductor, and would therefore retain the fine powder. He could then transfer the powder to a fresh sheet of paper, resulting in a duplicate of the original. This approach would give his invention an advantage over the Photostat, which could only create a photographic negative of the original.

First_xerographic_copy_-_10-22-38_ASTORIA_ The world’s first xerographic image

On October 22, 1938, they had their historic breakthrough. Kornei wrote the words "10.-22.-38 ASTORIA." in India ink on a glass microscope slide. The Austrian prepared a zinc plate with a sulfur coating, darkened the room, rubbed the sulfur surface with a cotton handkerchief to apply an electrostatic charge, then laid the slide on the plate, exposing it to a bright, incandescent light. They removed the slide, sprinkled lycopodium powder to the sulfur surface, softly blew the excess away, and transferred the image to a sheet of wax paper. They heated the paper, softening the wax so the lycopodium would adhere to it, and had the world’s first xerographic copy. After repeating the experiment to be sure it worked, Carlson celebrated taking Kornei out for a modest lunch.

Kornei was not as excited about the results of the experiment as Carlson. Within a year, he left Carlson on cordial terms. His pessimism about electrophotography was so strong that he decided to dissolve his agreement with Carlson that would have given Kornei ten percent of Carlson’s future proceeds from the invention and partial rights to the inventions they had worked on together. Years later, when Xerox stock was soaring, Carlson sent Kornei a gift of one hundred shares in the company. Had Kornei held onto that gift, it would have been worth more than $1 million by 1972.

The road to his success—or that for xerography’s success—had been long and filled with failure. From 1939 to 1944, his funding requests were turned down by more than twenty companies. He tried for some time to sell the invention to International Business Machines (IBM), the great vendor of office equipment, but no one at the company saw merit in the concept—it is not clear that anyone at IBM even ‘understood’ the concept. His next-to-last attempt to garner the interest—and funds—he needed to commercialize the physics was a meeting with the Department of the Navy. The Navy had a specific interest in the production of dry copies but they did not "see" what Carlson saw.

On October 6, 1942, the Patent Office issued Carlson’s patent on electrophotography.


Xerographic Process Explored

Xerographic_photocopy_process_en_svg Schematic overview of the
xerographic photocopying process.

The first commercial use was hand processing of a flat photosensor with a copy camera and a separate processing unit to produce offset lithographic plates. Today this technology is used in photocopy machines, laser printers, and digital presses such as Xerox iGen3 and Xeikon presses which are slowly replacing many traditional offset presses in the printing industry for shorter runs.

By using a cylinder to carry the photosensor, automatic processing was enabled. In 1960 the automatic photocopier was created and many millions have been built since. The same process is used in microform printers and computer output laser or LED printers.

The steps of the process are described below as applied on a cylinder, as in a photocopier. Some variants are described within the text. Every step of the process has design variants.

A metal cylinder is mounted to rotate about a horizontal axis. This is called the drum. The end to end dimension is the width of print to be produced plus a generous tolerance. The drum in the copiers originally developed by Xerox Corporation were manufactured with a surface coating of amorphous selenium (more recently ceramic or organic photo conductor or OPC), applied by vacuum deposition. Amorphous selenium will hold an electrostatic charge in darkness and will conduct away such a charge under light. In the 1970s, IBM Corporation sought to avoid Xerox’s patents for selenium drums by developing organic photoconductors as an alternative to the selenium drum. The organic system, Photocopiers which rely on silicon or selenium (and its alloys) are charged positiive and use negative toner. Photoconducters using organic compounds (e.g., zinc oxide or cadmium sulfide), are vice versa. Organic photoconductors are now preferred because they can be deposited on a flexible, oval or triangular belt instead of a round drum.

Laser printer photo drums are made with a doped silicon diode sandwich structure with a hydrogen doped silicon light chargeable layer, a boron nitride rectifying (diode causing) layer that minimizes current leakage, as well as a surface layer of silicon doped with oxygen or nitrogen, silicon nitride is a scuff resistant material

The drum rotates at the speed of paper output. One revolution passes the drum surface through the steps described below.

Step 1. Charging…
An electrostatic charge of -600 volts is uniformly distributed over the surface of the drum by a corona discharge from a Corona unit (Corotron), with output limited by a control grid or screen. The complete unit is correctly called a Screened Corotron or Scorotron for short. This effect can also be achieved with the use of a contact roller with a charge applied to it. Essentially, a corona discharge is generated by a narrow wire 1/4 to 1/2 inch apart from the photoconductor. A negative charge is placed on the wire, which will ionize the space between the wire and conductor, so electrons will be repelled and pushed away onto the conductor. The conductor is set on top of a conducting surface, kept at ground potential.

The polarity is chosen to suit the Positive or Negative process. Positive process is used for producing black on white analogue copies. Negative process is used for producing black on white from negative “originalsF” (mainly microfilm) and all digital printing and copying. This is to economize on the use of laser light by the “Blackwriting” or Write to Black exposure method.

Step 2. Exposure…
The document or microform to be copied is illuminated by flash lamps on the platen and either passed over a lens or is scanned by a moving light and lens, such that its image is projected onto and synchronized with the moving drum surface. Where there is text or image on the document, the corresponding area of the drum will remain unlit. Where there is no image the drum will be illuminated and the charge will be dissipated. The charge that remains on the drum after this exposure is a ‘latent’ image and is a negative of the original document. Alternatively, the image may be Flash Exposed, using a Xenon strobe, onto the surface of the moving drum or belt, fast enough to render a perfect latent image.

Whether in a scanning or a stationary optical system, combinations of lenses and mirrors are used to project the original image on the platen (scanning surface) onto the photoconductor. Additional lenses, with different focal lengths or zooming lenses are utilized to enlarge or reduce the image. The scanning system, though, must change its scanner speed to adapt to elements or reductions.

A drum is inferior to a belt in the sense that although it is simpler than a belt, it must be buffered gradually in parts rolling on the drum. As a result, the belt is more efficient to use one exposure to make a direct passage.

In a laser or LED printer, modulated light is projected onto the drum surface to create the latent image. The modulated light is used only to create the positive image, hence the term “Blackwriting.”

Step 3. Development…
In high-volume copiers, the drum is presented with a slowly turbulent mixture of toner particles and larger, iron, reusable carrier particles. The carrier particles have a coating which, during agitation, generates a triboelectric charge (a form of static electricity), which attracts a coating of toner particles. In addition, the mix is manipulated with a magnetic roller to present to the surface of the drum/belt a brush of toner. By contact with the carrier each neutral toner particle has an electric charge of polarity opposite to the charge of the latent image on the drum. The charge attracts toner to form a visible image on the drum. To control the amount of toner transferred, a bias voltage is applied to the developer roller to counteract the attraction between toner and latent image.

Where a negative image is required, as when printing from a microform negative, then the toner has the same polarity as the corona in Step 1. Electrostatic lines of force drive the toner particles away from the latent image towards the uncharged area, which is the area exposed from the negative.

Early color copiers and printers used multiple copy cycles for each page output, using colored filters and toners. Modern units use only a single scan to four separate, miniature process units, operating simultaneously, each with its own coronas, drum and developer unit.

Step 4. Transfer…
Paper is passed between the drum and the transfer corona, which has a polarity that is the opposite of the charge on the toner. The toner image is transferred by a combination of pressure and electrostatic attraction, from the drum to the paper. On many color and high speed machines, it is common to replace the transfer corona with, one or more, charged Bias Transfer Rollers (BTRs), which apply greater pressure and produce a higher quality image.

Step 5. Separation or Detack…
Electric charges on the paper are partially neutralized by AC from a second corona, usually constructed in tandem with the transfer corona and immediately after it. As a result, the paper, complete with most (but not all) of the toner image is separated from the drum or belt surface.

Step 6. Fixing or Fusing…
The toner image is permanently fixed to the paper using either a heat and pressure mechanism (Hot Roll Fuser) or a radiant fusing technology (Oven Fuser) to melt and bond the toner particles into the medium (usually paper) being printed on. There also used to be available ‘Offline’ vapor fusers. These were trays covered in cotton gauze which was sprinkled with a volatile liquid, such as ether. When the transferred image was brought into proximity with the vapor from the evaporating liquid the result was a perfectly fixed copy without any of the distortion or toner migration which can occur with the other methods. This method is now outlawed by the ‘Health and Safety’ authorities, for obvious reasons.

Step 7. Cleaning…
The drum, having already been partially discharged during detack, is further discharged, by light, and any remaining toner, that did not transfer in Step 6, is removed from the drum surface by a rotating brush under suction, or a squeegee known as the Cleaning Blade. In most cases, this ‘waste’ toner is routed into a waste toner compartment for later disposal; however, in some systems it is routed back into the developer unit for reuse. This process, known as Toner Reclaim, is much more economical but can possibly lead to a reduced overall toner efficiency through a process known as ‘toner polluting’ whereby concentration levels of toner/developer having poor electrostatic properties are permitted to build up in the developer unit, reducing the overall efficiency of the toner in the system.

Note: Some systems have abandoned entirely the use of a separate developer (carrier). These systems, known as Mono Component, operate as above but use either a magnetic toner or fusible developer (however you wish to view it). This results in the complete removal of the need to replace worn out developer, as the user effectively replaces it along with the toner. An alternative developing system, developed by KIP from an abandoned line of research by Xerox, completely replaces magnetic toner manipulation and the cleaning system, with a series of, computer controlled, varying biases. The toner is printed directly onto the drum, by direct contact with a rubber developing roller which, by reversing the bias, removes all the unwanted toner and returns it to the developer unit for re-use.

The development of xerography has led to new technologies that some predict will eventually eradicate traditional offset printing machines. These new machines that print in full CMYK color, such as Xeikon, use xerography but provide nearly the quality of traditional ink prints.


Please take time to further explore more about
Chester Carlson and the Xerographic Process by accessing
the Wikipedia articles referenced below…



Background information is from Wikipedia articles on:

Wikipedia: Chester Carlson…

Wikipedia: Xerography…

Brainy Quote: Xerox Quotes…