  The
printing trade was well established even before Gutenberg's time,
using woodblock technology. A sheet of paper was placed on the
inked woodblock and an impression taken by rubbing - a complex
and time-consuming procedure.
The genius of Gutenberg's invention was to split the text into
its individual components, such as lower and upper case letters,
punctuation marks, ligatures and abbreviations, drawing on the
traditions of medieval scribes. These individual items were
then cast in quantity as mirror images and assembled to form
words, lines and pages.
The master
for each letter was cut into the face of a steel block, resulting
in a precise relief in reverse – the punch.
The next
step was to create a matrix by placing the punch on a rectangular
block made of a softer metal – usually copper - and striking
it vertically with a hammer-blow.
The resulting matrix was reworked and straightened to form
a right-angled cube. This true-reading image required a uniform
depth, achieved by filing over the surface. Gutenberg developed
a hand casting instrument to facilitate the casting of a character,with
two sections enclosing a rectangular casting channel, closed
at one end by the matrix. The resulting character was then de-flashed,
to remove excess casting material.
 Each
letter had a pre-determined breaking point to ensure that all
letters were of identical height.
The hand
casting instrument - the most significant element of the invention
- allowied the printer to quickly cast the required number of
a diverse range of characters . The metal used for casting was
an alloy of lead, tin and further admixtures, with attributes
that ensured rapid cooling and sufficient durability under the
high mechanical stresses of the press.
The printing press was a screw press, specially designed to
achieve an effective and even transfer of the image to paper
or even parchment – a quantum leap in speed and efficiency
compared with the previous method of taking impressions by rubbing.
Translation: John Burland
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