Paper

• 1. Introduction

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  Paper is a thin sheet of matted cellulose fibers, and almost everything about it is borrowed. Its name comes from papyrus, the reed-based writing surface of ancient Egypt, yet the two share no real ancestry. Papyrus is a lamination of natural plant fibre. Paper is something else entirely, manufactured from fibres whose properties have been changed by maceration.

  The process behind it is older than most empires. Papermaking developed in East Asia at least as early as 105 CE, and archaeological evidence points to paper-like material in China two centuries before that. From there it crossed the world, picked up legends, and eventually swallowed nearly every rival writing surface humans had ever tried.

  How did a slurry of dissolved pulp, drained and dried into sheets, beat out parchment, vellum, bamboo, and palm leaves? Why did the everyday paper of the past come from collected rags rather than trees? And what does it mean that the same material now turns up far more often as a cardboard box than as a written page?

• 2. Borrowed Name, Vanished Rivals

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  Cyperus papyrus, the plant, gave its name through a chain of borrowing. The English word descends from the Latin papyrus, which came from the Greek papuros, the term for that very plant. Egyptians and other Mediterranean cultures made writing material from its pith long before paper arrived.

  Papyrus carried fatal weaknesses. The plant grew primarily in Egypt, which tied the whole material to one geography. It was more expensive and more laborious to produce than paper. It was also fragile and sensitive to moisture, prone to break apart in damp conditions.

  Paper did not arrive into an empty field. It coexisted for a long time with parchment, vellum, barkcloth, birch bark, palm leaves, and bamboo and wooden slips. The oldest known archaeological fragments of paper's immediate precursor date to the 2nd century BCE in China, and the pulp papermaking process is ascribed to a 2nd-century CE Han court eunuch named Cai Lun.

• 3. The Talas Myth

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  The Battle of Talas in 751 CE is the moment popular history loves to cite. The story claims Tang dynasty papermakers were captured as prisoners, and that their captors extracted the secrets of the craft, spreading it into the Islamic world. It is a tidy tale, and it is wrong on the timeline.

  An archive of 76 paper writings in Sogdian, Arabic, and Chinese was found in Panjikent, left behind by the ruler Devastich before Arabs took the city in 722, a generation before Talas. Sogdian writing on paper has also turned up dating to 313 CE in Dunhuang. By the time Muslims first encountered paper in the 7th and 8th centuries, the material had already lived in the region for centuries.

  From Baghdad, where paper was being made by the late 8th century, the knowledge moved on. In the 13th century it spread from the Middle East into medieval Europe, where the first water-powered paper mills were built. Because it reached the West through Baghdad, Europeans first called it bagdatikos.

• 4. From Rags To Wood

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  Rag paper ruled before industrialization. The most common paper was made from discarded natural fibre textiles, gathered up by ragpickers who turned worn cloth into the raw stock for new sheets. It was a recycling economy long before the word existed.

  Wood changed everything. In 1844, the Canadian inventor Charles Fenerty and the German inventor Friedrich Gottlob Keller independently developed processes for pulping wood fibres. Paired with the Second Industrial Revolution, this 1843 invention of wood pulp made pulpwood paper the dominant variety to this day, and it sharply cut the cost of manufacturing through the 19th century.

  The chemistry of pulping split into two families. Chemical pulping uses a cooking liquor to dissolve lignin and wash it from the cellulose, which preserves fibre length. The sulfite process dates to the 1840s and dominated before the Second World War. The kraft process, invented in the 1870s and first used in the 1890s, became the most common method, partly because its reaction with lignin produces heat that can run a generator.

• 5. Inside The Pulp

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  Mechanical pulping keeps the lignin and pays for it later. In the thermomechanical process, wood is chipped and fed into steam-heated refiners, where chips are squeezed into fibres between two steel discs. The groundwood method presses debarked logs against rotating stones. Yields run above 95%, but the lignin makes the paper turn yellow and grow brittle over time.

  Justus Claproth, a German jurist, invented a process for removing printing inks from recycled paper in 1774. Today it is called deinking. Recycling works by mixing paper with water and applying mechanical action, which breaks the hydrogen bonds so fibres separate again.

  Recycled fibre falls into three classes. Mill broke is the substandard or grade-change paper a mill re-pulps internally. Preconsumer waste is offcut and processing scrap, such as guillotine trims and envelope blanks, generated outside the mill. Postconsumer waste is fibre from paper that already served its purpose, including office waste, magazine papers, and newsprint. Most recycled paper still contains some virgin fibre for the sake of quality.

• 6. Weight, Grain, And Standards

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  A caliper measures paper's thickness, given in thousandths of an inch in the United States and in micrometres elsewhere. Sheets may run between 0.07 and 0.18 mm thick. Density ranges from 250 kg/m3 for tissue paper up to 1500 kg/m3 for some specialty papers, with printing paper around 800 kg/m3.

  Weight is measured differently across the world. In the United States it refers to the weight of a ream of 500 sheets at a basic size before cutting, so a ream of 20 lb, 8.5 by 11 inch paper weighs 5 pounds. In regions using the ISO 216 system, weight is given in grams per square metre, with printing paper generally between 60 and 120 gsm and anything over 160 gsm counted as card.

  ISO 216 measures sheets by surface area, not by width and length. First adopted in Germany in 1922, it spread as nations went metric. A0 covers one square metre at roughly 1189 by 841 mm, and each smaller size is half the one above it. Heavier stock even shapes perception: sensory marketing research links a thicker sheet to higher perceived quality and brand prestige.

• 7. The Cardboard Turn

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  Paper-based storage of information has nearly vanished as a share of the whole. It held 0.33% of the world's total in 1986 and only 0.007% by 2007, even as absolute paper storage capacity rose from 8.7 to 19.4 petabytes. Paper postal letters made up less than 0.05% of global telecommunication capacity in 1986, falling sharply after digital technologies arrived.

  The environmental ledger is heavy. Worldwide paper consumption has risen 400% over the past 40 years, and 35% of harvested trees go to paper manufacture. Paper waste reaches up to 40% of total US waste each year, some 71.6 million tons, while the average US office worker prints 31 pages a day and Americans use roughly 16 billion paper cups annually. Bleaching pulp with elemental chlorine releases chlorinated dioxins, persistent pollutants regulated by the Stockholm Convention.

  The page is losing, but the box is winning. The Food and Agriculture Organization reports that Asia has overtaken North America as the top producing continent. Graphic paper has declined from its mid-2000s peak to below 100 million tonnes a year. Meanwhile paperboard, including cardboard, has soared past 320 million tonnes, lifted by e-commerce since the 2010s and pushed further by COVID-19 lockdowns.