What is photocopying and how does it work? | Explained Premium

Xerography revolutionised the way we copy, print, and distribute textual material. It allowed for the quick and cheap reproduction of printed material, and enabled the emergence of a vibrant arts scene, improved access to educational material, and, perhaps most importantly, rendered copying an independent activity. It also had a hand in prompting better anti-counterfeiting measures and circumventing censorship.

The German philosopher Walter Benjamin wrote these words in his landmark 1935 essayThe Work of Art in the Age of Mechanical Reproduction. While Benjamin’s thesis centred on the character of art in a capitalist society and the effects of mass reproduction – and reproducibility – on it, it’s tempting to see parallels to the effect that photocopying had on the production and availability of textual material in the modern era.

Broadly, photocopying is a set of techniques with which to duplicate some content using, among other things, light. However, the contemporary colloquial use of the word ‘photocopying’ refers almost exclusively to xerography.

Both the word ‘xerography’ and the name ‘Xerox’ come from the Greek root-word ‘xero’, meaning ‘dry’. This is because xerography is a type of photocopying method whose process doesn’t involve messy liquid chemicals. Xerographic machines are in ubiquitous use around the world today to quickly and cheaply reproduce printed material.

Xerography has a few basic elements.

The first is the photoconductive surface – a surface coated with a photoconductive material. Such a material, when exposed to light, allows electrons to flow through it (i.e. conducts electricity) but blocks them when it’s dark.

This surface is negatively charged by placing a thin negatively charged wire with a high voltage next to it.

Then, the sheet of paper to be copied is illuminated with a bright light. The darker parts of the paper – where something is printed, i.e. – don’t reflect the light whereas the unmarked parts do.