The printing press
Early printing presses were modelled on existing presses, which had been used for hundreds of years to press grapes or olives, and had been used for printing wooden blocks before the invention of movable type. They were called 'platen' presses after the German word for the plate used to apply the pressure.
A screw mechanism was used to apply firm and even pressure to the dampened paper that was placed on top of the inked type. In order to get a good print impression it was important that each individual letter was at the same height. A piece of felt was stretched across an iron frame called a 'tympan' to allow a certain amount of give between the paper and the platen. A frame called a 'frisket' was used to mask off the edges of the type-set portion of the page, preventing ink splatters from getting on to the margins of the page.
Type was arranged and set into a frame, which rested on the heavy stone 'bed' of the press, and this was slid under the platen on horizontal tracks. Once in position the pressman would turn the screw to force the paper onto the inked surface. Once the impression had been made, the screw was wound up to raise the platen and the bed rolled out from beneath the press. The frisket and tympan were then raised allowing the newly printed paper to be removed and hung up to dry. A skilled pressman could achieve 200 impressions in an hour.
After printing, the sheets were hung up to dry. Once the ink had thoroughly dried, the sheets could be put through the press again, to print the other side, or to print a second colour.
In 1472 the printer Georg Lauer in Rome invented a moving carriage that allowed full sheets to be printed with two pulls of the press, instead of a press that allowed only one folio page, or two quarto pages (i.e. a half-sheet) to be printed together. The use of the improved press spread slowly northward from Rome.