(Written by N.R. Jayaraman)
widely used by general public, business houses, education institutions, and
other governmental departments is a process that facilitates replica of the originals
through specialized machine called Photo copier, which in general is called
The process of Xerox photo copying was reportedly invented in the
year 1938 by an American physicist called Chester F. Carlson, a patent attorney
in New York, though the world’s first photo copier in the name of Xerox machine was introduced by a U.S firm in 1960s. Prior to the invention of photo
copiers, duplicating the originals were done by manual process involving carbon
paper, exposing chemical coated paper, mimeograph machines and other duplicating processes, but the problem of copying the illustrations remained a big problem.
If one go through the history of copying they will be surprised to know that the copying of documents is not new
phenomenon and was existing even during 2500 B.C.
when scribes of Babylon and Egypt and copy clerks of Victorian era reportedly
used quills, pens and small tools to copy the documents on to clay,
material, parchment sheets etc for preserving information.
the bygone era, say 500 to 600 years back the inscriptions found on the
culverts and shrine
walls were medium for taking prints by several
historians and scholars, who were unable to take photo copies of the
inscriptions (in view of lesser knowledge of photography in those
days) for authenticating the texts found on the culverts or shrine
walls. They used to rub charcoal on the surface and pressed semi moist
paper on them to get prints for study and analysis in leisure.
Black Charcoal powder rubbed on the stone inscriptions
and semi moist paper pressed against it to get prints
As the time
passed, instead of on clay, papyrus material, parchment sheets
etc copying on paper commenced. Throughout 20th century, the photo copying in the name of Xerography
remained one of the most sought after techniques by the industries and
researchers for documentation purposes especially in Libraries and Universities. Fax machines, digital printing etc were offshoots of Xerographic process in later
years. All theses processes come under the art of Reprographic Process. At one stage of time, the process of Xerox, the new invention in 1980s were part of Reprographic process and intended mainly for educational institutions, Research institutes, commercial and Governmental work.
Prior to this, sometime during 15-16th centuries, some people practiced the art of copying in a different style. The original drawings
were redrawn on to another paper using carbon like paper or a copy redrawn by the artists
themselves and either of them, either the original or the redrawn copy were carefully pin pricked to create holes on the
images to turn it into a stencil. Finely ground graphite or charcoal
powder tied inside fine muslin clothes was dusted over the pin pricked
areas to create image on to another semi moist paper kept below the pin pricked master to make few copies. The moist paper holding the finely dusted powders
when dried held the image on to it thus remaining as copies. This practice led to
the innovation of stencils in later era.
In the history
of copying, the copying process played important
role in the documentation of records and extensively used by the scientific
communities and scholars all over the world for research and to study
historical archives. The Engineers who drew the engineering drawings preferred
copies to make corrections on the copies without destroying the originals for
comparison. The copying process too helped in exchanging and circulating the
messages especially during war time and to use the duplicate copies for
litigation activities without destroying the original.
With the spurt in the research
activities gaining ground all over the world, publication activities of
research reports, scholarly journals and numerous other publications
accelerated tremendously. Since one cannot be expected to keep the entire set of documents and only specific parts related to their scientific or
research work may be required, copies of the specific pages from all such documents were preferred both for personal reference
and to use as exchange material. It was also easier that the select copies thus obtained could be gathered,
collated, classified or categorized and stored for retrieval at appropriate
time for their relevant study. World over this facilitated the setting up of Documentation centers in the Scientific
and Research institutions and to support the Libraries in the
universities, colleges and schools etc which became the nerve centre for gathering
information from the stored material. Some reprographic equipments or facilities were
therefore needed in such places to instantly take prints from the culled material.
Reprographic techniques enabled
one to obtain several or even a single copy from the culled original document,
the photo copies that resembled the original in all respects including the contents in the original,
baring the size so that they can be verified appropriately as and when needed.
The second most important aspect of photo copying was that several of the documents
were available in different languages and needed to be got translated
from different places, the diagrams or drawings, especially the maps cannot be
hand copied as even the minor error in reproduction can alter the
subject. Therefore the reproduction of all kinds of documents cannot be done
manually in entirety and some equipment or systems suitable to pick up and give
true contents of the documents on another paper were needed whether one
understood the language or not.
These factors lead to the ever
increasing demand for the invention table top, time saving and quick to
reproduce copying systems both for public use and Libraries and Documentation
centers. Initially all the machineries and equipments used for these purposes
were categorised as Reprographic equipments, Reprography meaning reproduction
of documents. The initial set of eon back processes involved production of
copies either in paper form or on storable, space saving films like Micro
filming in 35 and 16 mm sizes and Microfiche which is a sheet of film, usually
the size of a filing card, on which several pages of the books, newspapers,
documents, etc, could be recorded in miniaturized form.
Prior to emergence of Xerographic process of copying, centuries ago several other processes
for producing copies existed but most of which are now extinct and some have gone into
obliteration. Some of those short lived
processes include the following:-
Ammonia and Blue print process where in specially treated chemical paper is
exposed under the tracing paper and the chemically treated paper put in the
ammonia gas chamber to produce copies containing white images on blue
background (negative image). They were mostly used for production of copies from Engineering drawings and Maps.
Pellet Process is similar to blue print process, but produced positive image on
paper. A paper sensitized with ferric salts is exposed to UV light under a
translucent paper that contained images and then washed in ferrocyanide bath. A
positive reading blue image in white background is derived from
original drawing on translucent tracing paper, without requirement of an intermediate
Diazo process, again similar to Blue printing process, but involving paper
sensitized with different other chemical called diazonium salts. The treated
paper exposed under tracing paper and developed in ammonia gas chamber produce
copies- Blue image with white background.
Ferro Gallic Acid process is similar to blue print process that produces positive
prints on paper. A paper sensitized with ferrochoride and tartaric acid and gum
is exposed to UV light under a translucent paper that contains images and then
washed in Gallic acid bath and water. A brownish print is derived from original drawn on translucent tracing paper, without
needing an intermediate negative.
process where in a specially treated paper was converted into a stencil with
special ink to reproduce multiple copies.
- Edison Stencils prepared using fine needle through a motor driven unit and then
using it as stencil. The needle was called Edison electric pen.
- Heavy wax coated paper used as a stencil to cut the image with a hard nipped pen
or knife to create pin hole and force the ink to pass through. This stencil was fixed on a machine
called Mimeograph and copies taken. However the stencil could not accept the
hand written text material.
Mimeograph process is another stenciling process. The
matter is typed directly on a waxed mulberry
paper without ribbon on a Mimeograph typewriter machine. The wax coating on paper gets removed thereby causing pinprick like holes in the areas of the text material. Once prepared,
the stencil is wrapped around the ink-filled drum of the rotary or flat machine
and Turkey Red oil based ink is forced through the
holes onto the paper. Early flatbed machines used a kind of squeegee. This
process was known as Mimeograph process.
- Polygraph process in which duplication of the document is done with a second
pen moving parallel to one held by a writer as it is written.
- Invented in
Russia, the Hektographic process in which a master copy i.e. gelatine pad is
imaged or written with special ink made of Aniline dyes. Then the sheets of
fresh paper could be laid on top of the dye impregnated gelatine to transfer
the image. This was good for short no of copies and was a slow process.
followed Spirit duplicating process called Ditto in which the the matter was
typed or drawn on a special non absorbent, dye coated master paper. The image
carrying paper was clamped on table top equipment fitted with a drum. With each
rotation the moisture of the master sheet dissolved small faction of dye on to
the paper producing copies, text material purple coloured. Often mistakenly
referred to as mimeograph machines, spirit duplicators was invented in the
1920’s. Instead of ink, a solvent on each sheet of paper would dissolve some of
the pigment from the stencil, with purple being a common color due to its
- Photostat paper exposed through the process camera that produced white letters
on black background. Since this could reproduce text to line work to
illustrations it was used to take several prints for researchers for documentation
Photostat Camera with Prism to get readable copies
Photostat Print - Black background
with white letters (Negative print)
- Kodograph process in which instead of negative working Photostat paper the auto
positive paper was used to get positive prints directly from originals, even
from worn or weak tracings in ordinary room light without negatives. The paper
was known as Kodak Photostat positive paper.
Kodograph Print - Black letters
on white background (Positive print)
- A reflex copying process called Reflectography, in which a special coated
silver gelatine paper is placed face down on the printed matter, pressed into
contact and exposed through the back of the silver paper. The light passing
through the paper is reflected back from the white surface of the documents and
reacts with the silver coated paper. On development it gave negative image i.e.
white letters on dark background.
duplicating process developed by 3M called Adherography in which the images
were formed by the adherence of powder to a tacky latent image created by the
effect of infrared heat. This provided a master from which 200 to 250 copies
could be made. The powder image of the resulting print was fused to the paper
Thermo-Fax photocopying technology is based on dry silver process introduced by
3M. A thin sheet of heat sensitive paper is placed on the original
document to be copied, and exposed to infrared energy. The image areas in the
original absorbed the infrared energy when heated and then transferred the heat
on to the heat sensitive paper supplied by 3M thus producing a black
image copy of the original.
RCA (Radio Corporation of America) introduced Electrofax which used Zinc Oxide
coated paper that held the electrostatic charge similar to selenium plate
holding the electrostatic charge. The original when exposed to the zinc oxide
paper removed the charges from the non image areas and black toner particles
adhered to the areas still retaining the charge and fused them to stick on to
the paper thus producing copies with black image.
Finally when the Xerographic process surfaced in the year 1949, many firms came
out with various models with different processes. Broadly the theory of
Xerography is that a Electro photographically charged photosensitive selenium
plate carried the images and accepted special toner powder and then to transfer them again on
to a paper when reverse charged. The toner gets fused by heat and remain adhered to the
paper firmly. Initially the photo copying machines were inbuilt with flat surfaced
selenium plates, but as the developmental activities progressed, cylindrical
selenium drums were incorporated instead of flat surfaced plates on the machines. Subsequently colour photo copies emerged. After years of research Canon invented another technology which replaced photo sensitive selenium with that of Cadmium Sulphate with a hard insulating coating that had higher durability.
The second improvement made by Canon is on the Toner, a dry powder that forms
the printed text and images on the paper on photo copiers and printers. The
toner used on the copiers is a mixer of carbon powder, iron oxide, and sugar.
The particles in the toner that form the images are melted by heat to bind the
images on to the paper. Originally when the photo copiers were invented the
particle size of toners used to be around 14–16 micrometers or little more. In
order to further improve the print quality reductions in particle size to
produce finer resolution prints were developed by Canon through the application
of new technologies such as Emulsion-Aggregation. Toner manufacturers maintain
a quality control standard for particle size distribution in order to produce a
powder suitable for use in their printers.
With the advent of digital printing in the copying process that print copies even on reels of paper process like blue printing has become irrelevant.