A mimeograph was a machine used to make copies of documents before photocopiers and computer printers existed. Teachers and office workers would type or draw on a special stencil sheet, then attach it to the mimeograph, which would push ink through the stencil onto fresh sheets of paper. One stencil could produce hundreds of copies.

If you've ever noticed that older books sometimes mention the distinct smell of freshly copied papers being handed out in class, they're talking about mimeographs. The copies came off the machine slightly damp, with a purple or blue ink that had a sharp, chemical odor. Many people who went to school between the 1950s and 1980s remember that smell vividly.

While mimeographs are now obsolete, replaced by faster and cleaner copying technology, they represented a revolution in their time. Before mimeographs, someone wanting to give thirty students the same worksheet would have to write it out by hand thirty times or have it professionally printed, which was expensive. The mimeograph made it possible for teachers to easily create and distribute materials to entire classes.