Electrophotography (EP) is the most common process among the group of electrostatic printing processes. Electrophotography manipulates electrical charges and light to fuse toner particles onto a substrate in the form of an image or text via a photoreceptor drum or a metal roller coated in material that conducts light. The process was invented in 1938 by Chester Carlson. Carlson was investigating the electrostatic properties of metals in order to invent a faster, easier way of copying documents. 

Early systems were used primarily for this purpose and required some manual steps, but by 1959 the first fully automatic system was introduced for office use. In the 1960s, and through the 1980s, some artists adopted the technology for image making, which is often referred to as “copy art,” “electrographic art,” “photocopy art,” “electroworks,” and “xerography.” The copies/images are generally low quality and monochromatic (black and white).  In 1973 the first color copier was introduced, which also required manual steps, but in 1978 an automatic copier hit the market. In the early 1980s digital desktop electrophotographic printers and digital copiers for office use were introduced. In the early 1990s the first digital press for high-speed, high print run commercial printing, as well as print-on-demand applications, was introduced. 

There are two types of electrophotographic technologies: analog and digital. These systems can be further subdivided into dry toner and liquid toner systems. Liquid toner copiers are commonly known as digital offset presses. Dry toner is used in office machines, digital presses, and desktop printers. 

The technology for analog and digital, dry and liquid toner eletrophotographic systems are similar. A photo-conducting drum, called a photoreceptor, is given a uniform electrical charge by a corona (electrical discharge). Light exposes the drum, selectively discharging it and creating a latent image. The analog system uses an optical lens-light system by which the original document is scanned with a bright light and the reflected image is exposed onto the photoreceptor through a system of mirrors and lenses. In the digital system a light sensitive electronic chip called a charge-coupled device (CCD) converts light into an electronic signal used to control either a laser beam or light emitting diode (LED) that exposes the photoreceptor. The original document may be a scanned paper document or a digital file. 

Toner is then applied to the surface of the drum. Dry toner consists of pigment or dye suspended in thermoplastic resin particles. Liquid toner is similar but finer and is dispersed in a solvent. The toner also holds an electrical charge and adheres only to areas with the opposite charge. For example in write-white (charged-area development) systems the photoreceptor is given a positive charge and light discharges areas of the photoreceptor that correspond to the white areas of the image. The negatively charged toner is attracted to the areas where the positive charge remains. Alternately, in the write-black (discharge-area development) system, light discharges areas corresponding to the black areas and positively charged toner adheres to the areas of the drum where the charge has been discharged. In the dry toner system the toner is then transferred from the drum to the support (usually paper) and a second corona is positioned behind the paper which creates a charge greater than that of the photo-conductor. This pulls the toner from the drum to the paper. At this stage, the toner rests like a fine dust on the surface of the paper. Paper is passed between heated pressure rollers that fuse the toner to the surface. The paper is pushed out of the copier/printer and the toner cools and sets. 

In the liquid toner system the toner flows over the photoreceptor and is then transferred to a heated rubber blanket cylinder which evaporates the solvent and causes the thermoplastic resin to melt. The now sticky toner is transferred to the support, which is cooler, the toner adheres to the support, cools, and hardens. Finally, in each system, the toner is mechanically scraped from the photoreceptor drum and the drum is exposed to a light that neutralizes any remaining charge. 

Color eletrophotographic prints are made using cyan, magenta, yellow, and black toner (other colors are possible, but less common). Each color has to be exposed and printed separately. LED systems have four consecutive imaging systems for each color. Some laser printers have one photoreceptor drum that is imaged and the toner applied and transferred to the paper four times in succession. Some digital presses require the four, color images to be transferred to the blanket and then transferred to the paper support together.