Electrofax
Encyclopedia
An electrofax is an electrostatic printer and copier technology where the image is formed directly on the paper, instead of first on a drum (and then transferred to paper) as it would be in xerography
. It was used in the United States
from the 1950s through the 1980s.
The paper used in this process is coated with a zinc oxide
powder, adhered with a resin
in order to make it able to hold an electrostatic charge, absorb toner
to form an image, and allow the evaporation of toner dispersant
s. Users of electrofax machines purchased such paper with the coating already applied.
In copiers, the paper, typically fed from a roll, is given a static
electric charge
, after which it is exposed to light reflected from the original document and focused through a lens
; the zinc oxide particles either preserve or discharge the electric charge, depending on the amount of light which reaches them. After exposure
, the paper is passed through a toner station where toner, typically carbon black
suspended in an organic
liquid known as a dispersant, is spread over the paper. Where charged areas remain on the paper, the black toner particles adhere; where the paper is discharged, they do not. A knife then cuts the paper to the proper length (typically letter or legal size). The now free sheet of paper then passes out of the toner station where excess dispersant is wiped off. Typically, the paper is sent to an output tray where any remaining dispersant evaporates, leaving the copies with a faint "kerosene
" odor.
In printers
and plotter
s, the paper is typically electrostatically charged by passing it over bar containing hundreds or thousands of charging contacts. The image is formed by either applying or removing a charge from each contact individually as the paper passes over it. This leaves a grid of charged dots on the paper. Toner is then applied as described above.
This technology was first developed at RCA
(Radio Corporation of America) in the early 1950s. Later, many office machine companies, including SCM (Smith Corona Marchant), Savin, etc. introduced copiers that utilized it. Versatec was one brand of computer printer
s and plotter
s that also had machines that used this process.
Copying machines using electrofax were common from the 1960s through the 1980s. During that time, they were less expensive to manufacture than xerographic copiers, although the paper was slightly more costly than the plain paper used by xerography. As soon as other copier technologies could produce markedly better quality copies and became less expensive, electrofax fell out of favor. Electrofax, by comparison, suffered from a number of drawbacks, including weak blacks in the image (most machines could only produce a dark gray), the dampness and odor of the copies, the need for special paper, and multiple-bottle liquid toner replacement. Likewise, as laser printer
s became lower in cost, followed by inkjet printer
s, the need for electrofax based printers & plotters faded.
Xerography
Xerography is a dry photocopying technique invented by Chester Carlson in 1938, for which he was awarded on October 6, 1942. Carlson originally called his invention electrophotography...
. It was used in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
from the 1950s through the 1980s.
The paper used in this process is coated with a zinc oxide
Zinc oxide
Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
powder, adhered with a resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
in order to make it able to hold an electrostatic charge, absorb toner
Toner
Toner is a powder used in laser printers and photocopiers to form the printed text and images on the paper. In its early form it was simply carbon powder. Then, to improve the quality of the printout, the carbon was melt-mixed with a polymer...
to form an image, and allow the evaporation of toner dispersant
Dispersant
A dispersant or a dispersing agent or a plasticizer or a superplasticizer is either a non-surface active polymer or a surface-active substance added to a suspension, usually a colloid, to improve the separation of particles and to prevent settling or clumping...
s. Users of electrofax machines purchased such paper with the coating already applied.
In copiers, the paper, typically fed from a roll, is given a static
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...
electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
, after which it is exposed to light reflected from the original document and focused through a lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
; the zinc oxide particles either preserve or discharge the electric charge, depending on the amount of light which reaches them. After exposure
Exposure (photography)
In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...
, the paper is passed through a toner station where toner, typically carbon black
Soot
Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...
suspended in an organic
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
liquid known as a dispersant, is spread over the paper. Where charged areas remain on the paper, the black toner particles adhere; where the paper is discharged, they do not. A knife then cuts the paper to the proper length (typically letter or legal size). The now free sheet of paper then passes out of the toner station where excess dispersant is wiped off. Typically, the paper is sent to an output tray where any remaining dispersant evaporates, leaving the copies with a faint "kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
" odor.
In printers
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
and plotter
Plotter
A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers...
s, the paper is typically electrostatically charged by passing it over bar containing hundreds or thousands of charging contacts. The image is formed by either applying or removing a charge from each contact individually as the paper passes over it. This leaves a grid of charged dots on the paper. Toner is then applied as described above.
This technology was first developed at RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
(Radio Corporation of America) in the early 1950s. Later, many office machine companies, including SCM (Smith Corona Marchant), Savin, etc. introduced copiers that utilized it. Versatec was one brand of computer printer
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
s and plotter
Plotter
A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers...
s that also had machines that used this process.
Copying machines using electrofax were common from the 1960s through the 1980s. During that time, they were less expensive to manufacture than xerographic copiers, although the paper was slightly more costly than the plain paper used by xerography. As soon as other copier technologies could produce markedly better quality copies and became less expensive, electrofax fell out of favor. Electrofax, by comparison, suffered from a number of drawbacks, including weak blacks in the image (most machines could only produce a dark gray), the dampness and odor of the copies, the need for special paper, and multiple-bottle liquid toner replacement. Likewise, as laser printer
Laser printer
A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers , laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced...
s became lower in cost, followed by inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
s, the need for electrofax based printers & plotters faded.