The knowledge of how to make it traveled along the network of trade routes that crossed the interior of Asia, carried by merchants, travelers, and craftsmen.
A well-known story links the arrival of papermaking in the city of Samarkand with events of the year 751, when, according to the account, Chinese papermakers came to the city and taught their craft there. Historians now regard the story with caution, since papermaking may already have been known in the region before that date. What is clear is that Samarkand became an important center of paper production in the eighth century, and that its paper was widely admired.
From Central Asia, papermaking spread across the Islamic world. A paper mill is reported to have been established in Baghdad at the end of the eighth century, during the reign of the caliph Harun al-Rashid. The growth of administration in the caliphate created a heavy demand for records, and paper was cheaper than parchment and less easily altered than papyrus, since erasures on paper tended to leave visible traces. Government offices adopted paper, and its use spread to scholarship, commerce, and the copying of books. Papermaking centers developed in Damascus, in Cairo, and in other cities. In Egypt, paper gradually replaced papyrus, which had been made there for thousands of years.
Papermakers in the Islamic world adapted the craft to local materials. Rather than mulberry bark, they relied largely on linen and hemp, often in the form of old rags and ropes. Rags were beaten into pulp, sometimes with the help of hammers driven by water wheels or by animals. Sheets were coated with a thin layer of starch to give them a smooth surface that would take ink well, and they were then burnished with a smooth, hard tool. The paper produced in this way was strong and smooth, well suited to the reed pens and inks used for writing in Arabic script.
Papermaking reached North Africa and from there crossed into Spain, which was then partly within the Islamic world. By the twelfth century, the town of Xativa, near Valencia, was known for its paper, and a geographer writing in the middle of that century praised its quality. From Spain, paper and the knowledge of making it passed gradually into other parts of Europe. For a time, paper was viewed with some suspicion in Europe, partly because it was associated with foreign trade and partly because it was thought to be less durable than parchment. Some authorities forbade its use for official documents.
The most important early center of European papermaking was the town of Fabriano, in central Italy, where paper was being made by the second half of the thirteenth century. The papermakers of Fabriano introduced several improvements that shaped the European craft for centuries. They used water-powered stamping mills, in which heavy wooden hammers, often fitted with iron or nails, rose and fell on the rags in deep troughs, beating them steadily into pulp. They replaced starch with sizing made from animal gelatin, which gave a harder surface that resisted the scratching of quill pens. They made moulds with screens of fine metal wire, which were more durable than the earlier screens.
The wire moulds of Fabriano also made possible the watermark. A design formed in wire and sewn onto the screen caused the pulp to lie slightly thinner over that area, so that the design appeared lighter when the finished sheet was held up to the light. The earliest known watermarks date from the late thirteenth century.