Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses, herbivore dung, or other vegetable sources in water.

Once the water is drained through a fine mesh leaving the fibre evenly distributed on the surface, it can be pressed and dried.

[not verified in body] It is a versatile material with many uses, including printing, painting, graphics, signage, design, packaging, decorating, writing, and cleaning.

The oldest known archaeological fragments of the immediate precursor to modern paper date to the 2nd century BCE in China.

The pulp papermaking process is ascribed to Cai Lun, a 2nd-century CE Han court eunuch.

[7] A process for removing printing inks from recycled paper was invented by German jurist Justus Claproth in 1774.

It was not until the introduction of wood pulp in 1843 that paper production was not dependent on recycled materials from ragpickers.

The kraft process, invented in the 1870s and first used in the 1890s, is now the most commonly practised strategy; one of its advantages is the chemical reaction with lignin produces heat, which can be used to run a generator.

In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones to be made into fibres.

Although large amounts of electrical energy are required to produce mechanical pulp, it costs less than the chemical kind.

Besides the fibres, pulps may contain fillers such as chalk or china clay,[12] which improve its characteristics for printing or writing.

In the earliest days of papermaking, this was done by hanging the sheets like laundry; in more modern times, various forms of heated drying mechanisms are used.

Coated paper has a thin layer of material such as calcium carbonate or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens.

Textured finishes, watermarks and wire patterns imitating hand-made laid paper can be created by the use of appropriate rollers in the later stages of the machine.

It is estimated that paper-based storage solutions captured 0.33% of the total in 1986 and only 0.007% in 2007, even though in absolute terms the world's capacity to store information on paper increased from 8.7 to 19.4 petabytes.

[15] It is estimated that in 1986 paper-based postal letters represented less than 0.05% of the world's telecommunication capacity, with sharply decreasing tendency after the massive introduction of digital technologies.

The thickness of paper is often measured by caliper, which is typically given in thousandths of an inch in the United States and in micrometres (μm) in the rest of the world.

In Europe and other regions using the ISO 216 paper-sizing system, the weight is expressed in grams per square metre (g/m2 or usually gsm) of the paper.

Alum was added to paper to assist in sizing,[24] making it somewhat water resistant so that inks did not "run" or spread uncontrollably.

Early papermakers did not realize that the alum they added liberally to cure almost every problem encountered in making their product would be eventually detrimental.

Paper made from mechanical pulp contains significant amounts of lignin, a major component in wood.

Dioxins are highly toxic, and health effects on humans include reproductive, developmental, immune and hormonal problems.

[35] In the 2022−2024 edition of the annual "Pulp and paper capacites survey", the Food and Agriculture Organization of the United Nations (FAO) reports that Asia has superseded North America as the top pulp- and paper-producing continent.

[36] FAO figures for 2021 show the production of graphic papers continuing its decline from a mid-2000s peak to hover below 100 million tonnes a year.

[36] FAO has documented the expanding production of cardboard in paper and paperboard, which has been increasing in response to the spread of e-commerce since the 2010s.

[37] Some manufacturers have started using a new, significantly more environmentally friendly alternative to expanded plastic packaging.

[39] Also, synthetics such as Tyvek and Teslin have been introduced as printing media as a more durable material than paper.