Captured prisoners at Talas probably did not bring papermaking west
A popular tale says the Islamic world learned papermaking in 751, when Chinese craftsmen taken prisoner at the Battle of Talas were forced to reveal the secret. Documents dig holes in it: Sogdian letters on paper from 313 CE turned up at Dunhuang, and a ruler at Panjikent left a paper archive behind before 722.
Paper itself is a mat of cellulose fibres, formed when a watery pulp drains through a screen and dries into a sheet. Its invention is credited to Cai Lun, a eunuch at the Han court, around 105 CE, though paper-like fragments in China go back to the 2nd century BCE. The name comes from papyrus, but that is a different technology: papyrus is layered strips of plant pith, while paper is made from fibres broken down and reformed. Papyrus lost out because the plant grew mainly in Egypt, cost more to process and fell apart in damp air.
By the late 8th century Baghdad had paper mills, and when the material reached medieval Europe in the 13th century, arriving by way of that city, it was at first called bagdatikos. Europeans added water-powered mills. For centuries the usual stock was rag paper, made from worn-out cloth gathered by ragpickers. In 1844 Charles Fenerty in Canada and Friedrich Gottlob Keller in Germany independently found ways to pulp wood, and wood fibre has dominated ever since.
Wood can be pulped two ways. Chemical methods cook out lignin, the glue that binds wood fibres, keeping the cellulose long and strong; the kraft process, now the most common, even generates surplus heat that many mills sell as electricity. Mechanical grinding keeps nearly all the wood and costs less, but the leftover lignin makes the sheet yellow and brittle with age, the familiar fate of old newsprint. A German jurist, Justus Claproth, worked out how to strip printing ink from used paper in 1774, the ancestor of today's deinking.
On a modern machine the wet web is pressed, then dried over long runs of steam-heated cylinders, sometimes more than forty, until less than six percent moisture remains. Handmade sheets betray themselves through laidlines, the fine ribs left by a wire or bamboo mould, and rough deckle edges. Paper's share of the world's information storage fell from 0.33 percent in 1986 to 0.007 percent in 2007, even as the total stored on it more than doubled.
Source: Paper
