Reprographic Processes- Origin and development

(Written by N.R. Jayaraman)

Photocopying, 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 Xeroxing.

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, papyrus material, parchment sheets etc for preserving information.  

In 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:- 
 Blue Print
 Photostat Camera with Prism to get readable copies

 Photostat Print - Black background 
with white letters (Negative print)

 Kodograph Print - Black letters
on white background (Positive print)
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.