A rotary printing press is a printing press in which the images to be printed are curved around a cylinder. Printing can be done on large number of substrates, including paper, cardboard, and plastic. Substrates can be sheet feed or unwound on a continuous roll through the press to be printed and further modified if required (e.g. die cut, overprint varnished, embossed). Printing presses that use continuous rolls are sometimes referred to as "web presses". Rotary drum printing was invented by Richard March Hoe in 1843, perfected in 1846, and patented in 1847. (Note – Some sources describe Parisian 'Hippolyte Auguste Marinoni', (1823, 7 January 1904) as the inventor of the Rotary printing press.) A.S. Abell and the Baltimore Sun was the first American user of the rotary press.
Today, there are three main types of rotary presses; offset including web offset, rotogravure, and flexo (short for flexography). While the three types use cylinders to print, they vary in their method.
Offset lithography uses a chemical process in which an image is chemically applied to a plate (generally through exposure of photosensitive layers on the plate material). Lithography is based on the fact that water and oil do not mix, which enables the planographic process to work. In the context of a printing plate, a wettable surface (the non-image area) may also be termed hydrophilic and (the image area) a non-wettable surface hydrophobic.
Gravure is a process in which small cells or holes are etched into a copper cylinder which is filled with ink.
Flexography is a relief system in which a raised image is created on a typically polymer based plate.
In stamp collecting, rotary-press-printed stamps are sometimes a different size than stamps printed with a flat plate. This happens because the stamp images are further apart on a rotary press, which makes the individual stamps larger (typically 1/2 mm to 1 mm).