Printing with movable type, a revolutionary departure from the old practice of copying by hand, was invented in the 1440s by Johannes Gutenberg, a German goldsmith. Mass production of identical books and pamphlets made the world of letters more accessible to a literate audience. Two preconditions proved essential for the advent of printing: the industrial production of paper and the commercial production of manuscripts. Increased paper production in the fourteenth and fifteenth centuries was the first stage in the rapid growth of manuscript books – hand-copied works bound as books – which in turn led to the invention of mechanical printing. Papermaking came to Europe from China via Arab intermediaries. By the fourteenth century, paper mills were operating in Italy, producing paper that was much more fragile but much cheaper than parchment or vellum, animal skins that Europeans had previously used for writing. To produce paper, old rags were soaked in a chemical solution, beaten by mallets into a pulp, washed with water, treated, and dried in sheets – a method that still produces good-quality paper today. By the fifteenth century, a brisk industry in manuscript books was flourishing in Europe's university towns and major cities. Production was in the hands of merchants called stationers, who supplied materials, arranged contracts for book production, and organized workshops known as scriptoria, where the manuscripts were copied, and acted as retail booksellers. The largest stationers, in Paris and Florence, were extensive operations by fifteenth-century standards. The Florentine Vespasiano da Bisticci, for example, created a library for Cosimo de' Medici, the head of Florence's leading family, by employing 45 copyists to complete 200 volumes in 22 months. Nonetheless, bookmaking in scriptoria was slow and expensive. The invention of movable type was an enormous technological breakthrough that took bookmaking out of the hands of human copyists. Printing was not new: the Chinese had been printing by woodblock since the tenth century, and woodcut pictures (in which an image is cut on wood and then transferred to paper) made their appearance in Europe in the early fifteenth century. Movable type, however, allowed entire manuscripts to be printed. The process involved casting durable metal molds to represent the letters of the alphabet. The letters were arranged to represent the text on a page and then pressed in ink against a sheet of paper. The imprint could be repeated numerous times with only a small amount of human labor. In 1467 two German printers established the first press in Rome and produced 12,000 volumes in five years, a feat that in the past would have required one thousand scribes working full time for the same number of years. After the 1440s, printing spread rapidly from Germany to other European countries. The cities of Cologne, Strasbourg, Nuremberg, Basel, and Augsburg had major presses, many Italian cities had established their own by 1480. In the 1490s, the German city of Frankfurt became an international meeting place for printers and booksellers. The Frankfurt book fair, where printers from different nations exhibited their newest titles, represented a major international cultural event and remains an unbroken tradition to this day. Early books from other presses were still rather exclusive and inaccessible, especially to a largely illiterate population. Perhaps the most famous early book, Gutenberg's two-volume edition of the Latin Bible, was unmistakably a luxury item. Altogether 185 copies were printed. First priced at well over what a fifteenth-century professor could earn in a year, the Gutenberg Bible has always been one of the most expensive books in history, both for its rarity and its exquisite crafting. Some historians argue that the invention of mechanical printing gave rise to a communications revolution as significant as, for example, the widespread use of the personal computer today. The multiplication of standardized texts altered the thinking habits of Europeans by freeing individuals from having to memorize everything they learned; it certainly made possible the speedy and inexpensive dissemination of knowledge. It created a wilder community of scholars, no longer dependent on personal patronage or church sponsorship for texts. Printing facilitated the free expression and exchange of ideas, and its disruptive potential did not go unnoticed by political and church authorities. Emperors and bishops in Germany, the homeland of the printing industry, moved quickly to issue censorship regulations.