On October 6, 1942, the U.S. Patent Office issued Patent No. 2,297,691 — "Electrophotography" — to a quiet, arthritic patent attorney named Chester F. Carlson. He had filed it on April 4, 1939, two years after producing the world's first dry copy in a rented room above a bar in Astoria, Queens. The image read: 10-22-38 ASTORIA. It is arguably the most consequential ten characters ever transferred between two surfaces.

What it does. Carlson's process was radically different from every duplication method that came before it. Wet photography, mimeographs, carbon paper, and Photostat machines all relied on chemicals, ink, or pressure. Carlson's invention used only static electricity and light:

• A plate coated with a photoconductive material (originally sulfur) is given a uniform electrostatic charge in the dark.
• An image is projected onto the plate. Wherever light hits, the coating becomes conductive and the charge bleeds away. The dark areas — the letters, the lines — retain their charge.
• A fine powder ("toner") is dusted across the plate. It clings only to the charged regions, forming a visible image.
• The powder is transferred to paper and fused with heat.

That is exactly how every laser printer, photocopier, and multifunction office machine works today. The OPC drum in your HP or Brother printer is a direct descendant of Carlson's sulfur plate. The toner cartridge is Carlson's lycopodium powder, refined.

Who he was. Carlson was not a chemist or a physicist. He was a patent examiner at P. R. Mallory who was tired of making hand copies of drawings. His hands were arthritic; the work was excruciating. He read every chemistry and physics textbook he could find at the New York Public Library and stumbled across the work of Hungarian physicist Pál Selényi on electrostatic image formation. Carlson's contribution was the synthesis: combine photoconductivity with electrostatic charge, and you could make a dry, instant, paper-to-paper copier.

The rejection era. Between 1939 and 1944, Carlson pitched his invention to IBM, Kodak, General Electric, RCA, A. B. Dick, and dozens more. Every single one passed. IBM's internal memo concluded there was "no apparent market" for an office copier. The Battelle Memorial Institute finally licensed it in 1944. A small photo-paper company called Haloid took a chance in 1947, renamed the process xerography (Greek for "dry writing"), and in 1959 launched the Xerox 914 — the first push-button office copier. Within six years, Haloid-Xerox revenue went from $32 million to over $500 million.

The modern echo. Carlson's patent did more than birth the photocopier. In 1969, Gary Starkweather at Xerox PARC realized you could replace the optical image with a laser scanned across the same charged drum — and the laser printer was born. Every page that exits a modern office printer still rides on Carlson's 1938 idea: a charged surface, a selective discharge, a clinging powder, a heated fuser. Even electrophotographic 3D printing (Selective Laser Sintering's electrostatic cousins) uses the same physics.

Carlson, who died in 1968, gave away roughly two-thirds of his $150 million fortune anonymously.