Papermaking is the process of making paper, a material which is used widely for writing and packaging. Almost all paper is prepared from cellulose. The most abundant form of cellulose is wood, and processes for extracting cellulose from wood is the objective of paper mills and pulping.
In papermaking, a dilute suspension of fibres in water is drained through a screen, so that a mat of randomly interwoven fibres is laid down. Water is removed from this mat of fibres by pressing and drying to make paper. Since the invention of the Fourdrinier machine in the 19th century, most paper has been made from wood pulp because of cost. But other fibre sources such as cotton and textiles are used for high-quality papers. One common measure of a paper's quality is its non-wood-pulp content, e.g., 25% cotton, 50% rag, etc. Previously, paper was made up of rags and hemp as well as other materials.
Papermaking is traced back to China about 105 CE, when Cai Lun, an official attached to the Imperial court during the Han Dynasty (202 BCE-220 CE), created a sheet of paper using mulberry and other bast fibres along with fishnets, old rags, and hemp waste. Paper with legible Chinese writings on it dating from 8 BCE, while hempen paper had been used in China for wrapping and padding since the eighth century BCE. Paper used as a writing medium became widespread by the 3rd century and, by the 6th century, toilet paper was starting to be used in China as well. During the Tang Dynasty (618-907 CE) paper was folded and sewn into square bags to preserve the flavour of tea, while the later Song Dynasty (960-1279 CE) was the first government to issue paper-printed money.