What was gutenberg's key innovation? how did it ?

He invented the movable type press, which (eventually) made books cheap enough for everyone to have a Bible. (Not a Gutenberg Bible, though... he went broke before he got the process perfected to the point of allowing mass production.)

Did he use lead in the ink, too?

Born 1399, died 1468.

Gutenberg's father was a metalworker who apparently had some connections to the mint in Mainz, and it was probably in his father's shop that he learned about metal casting and the use of punches. As an adult, Gutenberg seems to have experimented with using cast metal plates to print books, instead of the carved wood blocks much more commonly used. Somehow he got the idea to assemble printing masters from small units bound together, instead of casting a plate for a whole page at once. That was the key idea, but then he had to figure out how to make it practical. To achieve this, Gutenberg made four separate technological innovations, each brilliant:

the physical design of the type elements (their bodies had to fit flush against one another, the letter forms had to be of a uniform height from the type body to the printing surface, they had to be convenient enough to handle that a page could be assembled, etc.)a press that could accommodate a type form assembled from small, movable units of type bound togethera metal alloy for casting type (it had to be strong enough to make an impression without deforming, but flexible enough that thin elements such as serifs and swash finials wouldn't chip or snap off)an ink that would adhere to the metal type, yet transfer to vellum, parchment or paper cleanly and evenly, without smearing or spreading

Lack of any one of these (suitable type elements, suitable press, suitable type metal, suitable ink) would have rendered the innovation impractical. And did -- the Chinese experimented with printing from movable type in the 11th century C.E., using types made from clay, wood, or metal. But it was difficult to manufacture the types to be uniform, there was no press (they did hand-rubbings), and they used water-color inks that made a pale image and tended to bleed. This, plus the fact that over 1,000 different type elements were needed to render Chinese ideograms, caused the technology to be abandoned, and the Chinese went back to block printing from wood blocks carved to print a page at a time.

Gutenberg faced much greater challenges than someone inventing, say, movable type to produce modern Times Roman font would. Scribes of his period used brushes [and quills] to paint letters on expensive books; the letterforms showed complex variations in line weight as an artifact of relatively easy hand movements. The scribes added many edge marks and tiny squiggles that we'd recognize as apostrophes and accent marks today, and they used hundreds of easily-written shorthand symbols for common words to save themselves from RSI. Modern symbols like & and Xmas are among the few of these marks still in use.

To meet his customers' expectations, Gutenberg could not print books using only the 100 or so glyphs we'd now expect. And he could not simplify each glyph's shape into something easy to mold but hard to draw. This was long before folks had learned to continually adapt their culture to new technology, no matter how compelling its benefits: Gutenberg could not deliver the equivalent of a cheap dot-matrix printer. He had to match all this legacy manuscript baggage in his typefaces first before ever producing anything salable. --PCP

All of PCP's comments are true, except that I think you have to replace "brush" by "quill". Illuminations were, of course, painted, but I believe that most of the text in European books of the early 15th century was written, not drawn or painted. But the observation that Gutenberg was obliged to make his new technology emulate characteristics that were derived from the older technology is spot on. In fact, in some cities and provinces where the scribes' guilds were very strong, it was illegal to use printing technology (of any kind, even the wood-block variety) to mass-produces copies of books.

Hmm, that would make for interesting parallels to today, but I don't really feel like launching into it. Yeah. It's what the rest of this Web site's about ;-)

This invention has been used basically unchanged until the latter half of the 20th century, when the offset printing technique became popular. In essence, offset printing is a return to block printing, except that the blocks are replaced by metal plates. By using a photographical process, part of the plate is etched away, and the resulting plate can be used to print books.

The advantage is that you can use this to print a computer-generated page. Note, however, that the first typesetting programs were so inferior to human typesetters that DonaldKnuth felt himself obliged to write TeX, for the main purpose of correctly typesetting his magnus opus .