What Was the Gutenberg Process?
Before beginning work on the Bible around 1450, Gutenberg experimented with printing single sheets of paper and even small books, including a simple Latin grammar textbook. To this end, he created a printing press and developed a method of casting individual pieces of metal type.
Gutenberg’s press was made of wood and might have been modeled on wine-presses of his time. His type was made of a metal alloy that would melt at a low temperature but was strong enough to withstand being squeezed in a press. It was long thought that Gutenberg had originated the punch-matrix-mold system of typecasting used for centuries by subsequent type makers.
Recent research, however, indicates that he may have used a cruder sand-casting system in which the character is carved into the sand and the metal alloy is poured into this mold to create the type piece. This process would have been a long and laborious one because nearly 300 different pieces of type are used in the Bible, each one requiring its own sand-cast mold.
Once Gutenberg decided to make metal type, he began to search for the right metal. He finally settled on a mixture of lead and tin, an alloy that is easy to melt and cast, but which retains its shape under pressure. He also devised a method of making metal molds.
First, the letter was carefully cut, shaped and polished on the end of a copper or iron rod. Next, this was hammered into a soft metal, probably lead, where it left a negative impression. Then, the alloy for the type itself was melted and poured into the mold.
Besides this, Gutenberg also designed a tray into which the individual letters were assembled as words and clamped into place. The tray was sent into a hand press, inked, and squeezed down on the sheet of paper. We can see that Gutenberg did not invent just a method of making movable type.
He devised the entire process of printing from the typecasting and the mixing of the ink to the final steps of typesetting and stamping. Like all other basic inventions, it was revolutionary. Many copies could be made in a short time and then the same type could be removed and reassembled for another printing.