Paper

Paper is a sheet felted from loose plant fiber. Almost any cellulose — bark, rags, rope, straw — can be rotted, boiled, and pounded until it separates into individual fibers suspended in water. Dip a fine screen into that slurry, lift it flat, and a thin layer of fibers strands across the screen as the water drains away; those fibers, pressed and dried, tangle and bond into a single flat sheet. It is manufactured, not grown: unlike papyrus (a plant sliced and layered) or parchment (an animal skin scraped thin), paper can be made from waste, in any size, anywhere there is fiber and water.

Before paper, writing rode on expensive or awkward surfaces: silk was costly, bamboo and wood strips were bulky enough that a single book could fill a cart, papyrus grew only in Egypt, and parchment took a herd of animals to fill a library. Paper was cheap, light, foldable, and made from rubbish. That collapse in the cost of a writing surface is what let records, contracts, literature, and eventually printing spread to ordinary people rather than just palaces and temples. When the printing press arrived over a thousand years later, it needed a cheap surface to print on — and paper was already waiting.

Rot and boil the fiber soft, pound it in water until the water turns milky with freed fibers, then lift a thin film of that pulp out of the vat on a screen mould. Press the wet mats to drive out water, peel them apart, and dry them flat; a wash of starch or gelatin sizes the surface so ink writes clean. (See recipe.) The decisive, easily-missed step is the beating: paper's strength comes not from the plant but from fraying the fibers so thoroughly that they interlock as they dry.

Cheap paper made bulk record-keeping, bureaucracy, and correspondence practical, then made mass printing economical; the two together drove the explosion of books, newspapers, money, and paperwork that runs the modern world. It also became the substrate of banking and money-and-trade — banknotes, cheques, ledgers, contracts — and of science and law, which depend on the cheap, durable, copyable page. Nearly every institution that runs on the written word runs on this one felted mat of pounded fiber.