How Are Books Printed Today?
Printing technology has steadily grown in efficiency and ease since Gutenberg created movable type in the 1400s. The most common book printing method of today bears a strong resemblance to Gutenberg's technique, with several modern innovations. This method, called offset lithography, creates the vast majority of newly printed books.
Most historic printing presses share this basic function. Individual metal letter stamps are arranged together to form a page, and placed on a large cylinder. This cylinder rolls over an inkwell, coating the letters in ink, and then impresses upon a surface to transfer the text. Recently, computer scans have replaced the metal type, and typesetting is now done digitally. From these scans, a process called Photo Offset uses photochemical printing to create the cylindrical plates.
Metal vs. Rubber
In older presses, the metal cylinder transferred the ink directly to a paper page. Modern offset printing first impresses the cylinder against a rubber surface, which in turn is laid across the final book page. Since the rubber is softer than the metal type, the final text is sharper and clearer than books made in older presses . Even books printed from computers are made from rubber impressions.
Rather than individual letter stamps, the metal cylinder in modern presses uses a process called lithography. The text is printed on the cylinder in an oil based compound, and the entire smooth cylinder is covered in water. Since the oil and water do not mix, the text remains intact, and is covered with an ink that sticks only to the oiled sections of the cylinder. The cylinder then offsets the ink to the rubber surface where it can be transferred to paper.
Book pages enter presses as long rolls of paper. The pages print in a special order that allows them to lay in page number order when folded into a stack. Several such stacks make up a complete book, and older books were often identified by the number of pages per sheet. The spine-edge of the pages is left folded, and the other edges are cut so the pages may open.
For hardback books, the pages are sewn together near the spine, and glued into the cover. Paperback books are bound with a heat-sensitive glue.
- UCSC Department of Communication; Manuscripts, Books, and Maps: The Printing Press and a Changing World
- Old Tyme Offset Printing, A Short History of Offset Printing
- A New Introduction to Bibliography, Philip Gaskell, 1973
- University of Deleware, Lithography
- The Process of Offset Printing, What is Offset Printing?
- book image by charles taylor from Fotolia.com