What is Xerography? | History & Features!

Xerography, known as electrostatic printing, utilizes dry electrostatics to duplicate documents or images. It uses static electricity to produce copies without wet ink or direct contact.

Xerography Definition and Features

What is Xerography Technology and Its History?

Xerography is derived from Greek roots, which mean dry and writing. The term xerography means dry paper, reflecting its process. It differs based on chemical printing processes and utilizes photoconductivity. Photoconductivity is the ability of particular objects to conduct under light.

Silicon, germanium, and selenium absorb electrons from light, becoming weak electrical conductors. When voltage is applied, it enables the flow of electricity from atom to atom. Once the light is removed, they revert to being soft electrical conductors.

Xerography technology uses photoconductive selenium, aluminum, or other conductive metal backing layer.

Chester Carlson invented Xerography on October 22, 1938. Carlson graduated from the physics department and became a patent lawyer. In this job, he realized the need to create copies of documents quickly.

Later, Carlson experimented with materials that exhibited changes in electrical properties. These materials, known as photoconductive materials, were sensitive to electrostatic charges and light. In 1938, when he was 32 years old, he created the first xerographic image in his laboratory.

In 1947, Carlson discovered a small company in northern New York. With his invention, he acquired the rights to produce 4 billion pages of products. This technology later became the most widely used document printing method in offices.

How Does Xerography Work?

Static electricity charges the surface evenly. It is then exposed to light, which discharges or destroys the electric charge. This process leaves only shadow-charged areas.

It distributes powder pigment to the charged areas, making the image visible. Heat and pressure, then fix the ink on the form, completing the printing process.

Positive or negative ions electrostatically charge the layer. It depends on the polarity of the selected photoconductive insulating layer type. When a camera exposes the license plate, the light-receiving areas lose charges. So, this affects image capture and formation. It occurs based on the intensity they receive.

The charge retained on the plating layer creates an electrical or electrostatic model. So, this model represents and displays the image. The image forms when sprinkling a charged powder onto the exposed plate. This powder adds an opposite charge to the initial amount applied. In turn, it affects the plate and insulation layer.

The powder adheres to the charged areas, creating the print. Then, cover the plate with paper and apply a charge of the same polarity to the reverse side. So, this step helps in creating an electrostatic model. The dust image melts on the form when exposed to heat, thus fixing the image on the paper.

High-speed mechanized equipment performs all these operations in less than a second. Furthermore, the cost is cheap due to its reusable nature. As a result, the photoconductive insulating layer provides affordability.

Advantages and Disadvantages of Xerography

Advantages

Xerography is suitable for machines used in small, medium, or large offices. It allows text and graphics to be reproduced in seconds. It also offers variable image resolution for short to medium-sized jobs.

Users can use paper, cardboard, and transparencies easily without a CPU. Since the form does not need drying, users can feed it into the device. Additionally, the device provides support for stapling and double-sided printing.

Disadvantages

The main disadvantage of Xerography devices is that they use letter or A4 paper types. When the toner runs out, the printer leaves a blank white space. Additionally, users should allow some prints to cool as printouts may become extremely hot.

The Most Honest Questions About Xerography

How exactly does xerography work? Is there a magic wand?

Actually, it is all a dance of light and static electricity. First, a drum coated with selenium is filled with a positive charge in the dark. Then the image of the document is projected onto this drum.

The areas where light hits become conductive and dump their charge to the ground right away. The dark areas, which are the writing and lines, keep their charge. This creates an invisible electrostatic pattern on the drum.

So where does the toner powder come from? Negatively charged powder particles stick only to the charged areas. Then a piece of paper is laid over the drum and a reverse charge is applied from behind. The powder jumps to the paper at once. Heat and pressure then melt and fix this powder permanently.

Where did Chester Carlson get this idea? Is his story really inspiring?

Honestly, it is a true story of determination. Carlson was a physics graduate and a patent lawyer. He was sick of copying documents by hand. He started experiments in a back room in New York.

While playing with photoconductive materials, he saw that light changed electrical resistance. On October 22, 1938, he made the first dry copy in his makeshift lab in Astoria. That historic copy read “10-22-38 Astoria.”

In the end, he went from company to company for years trying to sell his invention. In 1947, a small company called Haloid licensed the technology. Haloid later changed its name to Xerox and shook the office world to its core.

No wet ink, no contact. So how does that powder stick to the paper?

The secret lies in opposite poles attracting each other. If the image on the drum is positively charged, the toner is negatively charged. It sticks tightly only to the charged areas.

Then a blank piece of paper is laid over the drum. A strong positive field applied from under the paper pulls the negative toner toward itself. The tiny powder grains leave the drum and jump to the paper.

Because the laws of physics are strict. In the final stage, the fuser unit does its job. Heat of about 200 degrees and pressure push the powder into the paper fibers. The paper comes out of the tray hot and fresh.

Why is this technology called ‘dry’? What is its advantage?

To be honest, the name says it all. In traditional printing, oily ink touches a plate and chemical processes are needed. In this process, you use dry powder. There is no water or solvent.

Plus, the copy dries right away. You do not have to wait like for print shop work. You can take the hot paper, staple it, and bring it to the boss right away. The drum is reused every cycle, so the cost is also quite low.

However, it only works with standard papers like A4 or letter. It is not good for huge posters.

Every office has a photocopier. What makes this device a must-have?

First of all, speed talks. A mechanical drum spins, exposes, and cleans itself in seconds. You can print hundreds of pages per minute. Plus, it does not need a complex chip like a CPU.

Also, it has skills like double-sided printing and overhead transparency copying. It fits different materials, from thick cardboard to thin paper. This flexibility gives office workers great freedom.

But it does not warn you when the toner is totally empty. Blank white pages suddenly start coming out and put you in a tough spot.

Does it have disadvantages too, or is it a perfect technology?

Of course, every technology has a cost. The biggest complaint is that the paper comes out too hot. Especially in the middle of summer, if you made 50 copies one after another, the papers burn your hands.

However, the photoconductive drum does not last forever either. If it gets scratched, black lines appear on copies. Replacing the drum hurts your wallet. Also, in damp places, toner clumps up and quality drops.

So you must keep the machine in a cool and dry place. Still, thanks to its speed and low copy cost, it remains the master of offices.

What is Xerography? | What are its History and Benefits?