How did Johannes Gutenberg invent the printing press?

It was one of the greatest triumphs of the Western World. In 1455, Johannes Gutenberg of Mainz, Germany, produced the first printed book in Europe using movable type - rows of reusable metal letters.

Up until the mid 15th century, all books had been handwritten - a highly-labor intensive and time-consuming process. By making it possible to produce multiple copies of books, Gutenberg's printing presses enabled new ideas in politics and religion to spread rapidly across Europe. His great achievement went beyond technological ingenuity and opened the floodgates of literature to a Renaissance world eager for knowledge.

Gutenberg's first major work was no ordinary book, but a Latin Bible - a vast project that had taken 15 years of toil, most of which was spent trying to raise the money. Furthermore, he was determined to keep his revolutionary invention a secret until his work was complete.

Striking the master set

Gutenberg's first challenge was to produce a complete master set of letters and characters some 270 in all, including capitals, lower case (small) letters, punctuation marks and various special characters and abbreviations. The letters and characters were carved in relief and in reverse on the tips of steel rods, which were later hardened by heating and then plunging into cold water.

This master set was used as a set of punches. Each character was hammered into a copper block called a "strike". This was fitted into the base of a larger mold and used as the eventual printing block. Each letter was given the appropriate spacing: "i", for example, needs less space than "w"'. A metal alloy, probably composed of lead, tin and antimony, was poured into the mold to produce a cast block of metal with the raised impression of the letter at its tip. Gutenberg could now cast individual letters and characters comparatively quickly.

The next stage was to sort the letters into compartments in a tray. The printer then picked out the letters and assembled the words line by line, ensuring that each line was the same length. This process could take a whole day to complete. When the text was ready, it was fitted into a frame to produce a stable, portable "forme" which was then laid on the base of the press.

Printing the pages

The next job was to ink the forme, using a blend of clear linseed oil varnish - which helped the ink to stick to the metal type - and lampblack for the black color. A pair of "inkballs" - leather pads, filled with wadding, attached to wooden handles – were lightly coated in the ink, then dabbed onto the type. The primer laid the paper over the forme, then turning a handle on the press, moved it into position. He then pulled a bar on the press, which operated the screw and applied even pressure over the forme. He then released the bar, removed the forme, peeled back the paper and stacked it next to the press. Gutenberg printed around 16 copies an hour in this way, and some 20 men kept six presses working full time for more than a year to produce the Bible.

While printing was under way, Gutenberg's main creditor. Johann Fust, called in his debts. Awarded in settlement all the materials and presses, Fust reaped the rewards of a brilliant invention, but Gutenberg's technological triumph was his own.