The printing press made its appearance around 1454, in the Mainz workshop of Johannes Gutenberg. After a great deal of trial and error, the technique of moveable type printing became commercially viable. The concept was simple: individual lead characters were assembled to create texts.
A worker would first fashion a steel punch, at one end of which was a character carved in relief and back to front. The punch would then be hammered into a small bar or block of copper, thus impressing an image of the letter into the metal. Type would then be cast from this hollow matrix using a specially-designed mould. From the start, a mixture of lead (about 75%), antimony (20%) and tin (5%) was used. Several thousand copies of each character would be cast and then arranged in a large, compartmentalised wooden drawer known as a type case. The work of composition could then begin.
This technical process invented by Gutenberg was perfected over time, and remained fundamentally unchanged until the Industrial Revolution.
A typesetter would sit at the type case. Next to him, a visorium held the text to be composed. In his hand, the typesetter held a composing stick on which he would compose the lines of text, letter by letter. After five or six lines, he would then place them in a galley. When all the pages needed for a quire were composed, the process moved to the imposition phase. The pages were arranged in a metal frame called a chase, bearing in mind that two printings would be required (one for the recto and one for the verso).
The chase was then brought to the printing press. While one worker inked the text using ink-balls, another lifted off the printed signatures, replaced them with blank sheets, operated the bed and turned the screw. The press platen came down and pressed the blank sheet against the freshly-inked sorts. This technical process invented by Gutenberg was perfected over time, and remained fundamentally unchanged until the Industrial Revolution.