A printing press is a device that uses pressure to transfer an image from some sort of prepared, inked surface to a receiving surface, like paper or cloth. It was one of the great inventions of the modern age, allowing books to be mass produced, helping to encourage the dissemination of information. Although predecessors existed for some time, the first true printing press was created by Johannes Gutenberg in 1439.
The invention of the printing press was largely encouraged by a growing demand for books in Europe, especially among the middle classes. Unable to afford the extremely expensive books handwritten on parchment, which could cost as much as a house or farm, students who were educated in reading and wanted to read on their own were unable to. Although screw presses existed at the time, and were widely in use in China, the actual printing press was a novel invention that helped drive down cost and make books available to those with a bit of money.
Gutenberg added a number of important contributions to the field of pressing and casting, rather than just combining existing technologies. Perhaps most impressive among these was a method of casting type out of an alloy of lead, antimony, and tin, by which type could be quickly cast from a template, reducing cost and allowing type to be more uniform. He also came up with a special oil-based ink, replacing the water-based inks used in woodblock prints, which lasted much longer. Gutenberg printed many books on his printing press, the most famous of which was his Gutenberg Bible, of which 48 copies still exist.
In the 1800s the printing press evolved yet again, with large cast iron presses taking the place of earlier presses, allowing for larger surfaces to be covered while requiring less force. The steam engine was later harnessed to remove the need for a human operator, capable of printing more than 1,100 pages an hour. The steam printing press began the era of mass newspapers, which in turn allowed the masses to become more literate, and to remain current on contemporary events. The rolling press followed, which could print literally millions of pages a day, allowing newspapers to become truly massive in their distribution.
By the 1930s, the printing press had reached an impressive efficiency, allowing for low-cost, high-volume productions, which made book printing much more affordable, and therefore allowed more books in a more diverse range of subjects to be printed. Further advances during the 20th century made books even more legible, and more affordable to print. The offset press, for example, transfers the original print to a soft rubber pad, which then imprints on the paper, creating a much more readable text. Offset printing remains the major type of printing used for modern book publishing, and although digital techniques are beginning to approach offset printing in terms of cost, their ability to create sheer masses of pages have not yet been matched. Some artisan books still continue to be pressed with a traditional letterpress, as well.