1. The types

Since the 18th century it has been noticed that not all individual impressions of Gutenberg's types are exactly identical. No comprehensive attempt had been made to explain this until very recently. An American physicist working with a bibliographer has undertaken a cluster analysis of digital images of individual impressions of a letters. They have concluded that Gutenberg's method was not the one which was in use at the end of the 15th century. This is a good illustration of how Gutenberg's invention of printing was the beginning of a process of refinement and improvements.

By the 1470s type was produced in way which remained unchanged for centuries. A letter was engraved onto a punch of hard metal. The punch was hammered into a softer metal, creating a matrix. The matrix was fitted into a mould and a piece of type was made by pouring in a lead and tin alloy. A type founder could thus produce hundreds of pieces of type, each with identical mirror images of the same letter or sign.

A printer would have many pieces of type for each letter, all leaving the same impression on the paper. They could be put together to form words, sentences, and pages. When enough copies of a page had been printed, the types could then be taken apart and used again to form new words, sentences and pages.

This proved one of the great advantages of printing. Otherwise it would not have been possible to produce many copies of the same text with speed and economy. In the 1470s an Italian bishop explained that three printers working for three months could produce 300 copies of a book. He estimated that it would have taken three scribes a lifetime each to complete the same number.

The type used by Gutenberg resembles a formal type of contemporary handwriting known as textura, because its strong vertical and horizontal lines gives the impression of the texture of a woven pattern across the page.

It measures 146 or 147 mm per 20 lines on the pages that have 40 lines to the page.
It was filed down to measure 138-140 mm per 20 lines on the pages that have 42 lines per page.
The typed area of the pages that have 40 lines per page measures 294 by 198 mm.
The typed area of the pages that have 42 lines per page measure 292 by 198 mm.
The typed area of the single page (fol. 310 recto) which has 41 lines measures 284 by 195 mm.

A resource on type-making has been made for the Huntington Library.

Paul Needham and Blaise Agüera y Arcas have examined how Gutenberg made his type, in

Blaise Agüera y Arcas, 'Temporary Matrices and Elemental Punches in Gutenberg's DK type' in Incunabula and Their Readers: Printing, Selling and Using Books in the Fifteenth Century, edited by Kristian Jensen (London: The British Library, 2003), pp. 1-12. ISBN 0712346769