paper
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What is paper?
Paper is a matted or felted sheet made from cellulose fibers that are formed on a wire screen after being suspended in water. Traced back to China around AD 105, papermaking slowly spread, reaching Central Asia by 751 and Europe by the 14th century.
The invention of the printing press in about 1450 dramatically increased the demand for paper. Though almost all steps in making paper are mechanized today, the basic process remains the same: creating pulp, filtering it, pressing it, and removing water.
The type of fiber, preparation of the pulp, additional materials, sheet weight, and treatments to the finished sheet determine paper grades and types. While wood is now the primary source, other fibers such as recycled wastepaper, straw, bamboo, and hemp are also used.
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What materials are used to make paper?
Paper is made from cellulose fibers, which are found in all plants. A variety of plant materials can be used, including wood pulp, bamboo, cotton, and linen. Recycled paper products are also a major source of paper fiber.
To make paper, the fibers are separated and wetted to create pulp. The pulp is filtered through a screen, creating a sheet of fiber that is pressed to remove water. The sheet is then dried and compressed.
Different types of paper are made using different fibers and preparation methods. Additives, such as coatings, pigments, or other substances, may be used depending on the paper's intended use.
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How is paper made in factories?
In factories, papermaking involves preparing a suspension of cellulose fibers by beating them in water. This separates the fibers and saturates them with water. The prepared stock is then filtered through a screen to create a matted fiber sheet. This wet sheet is pressed to squeeze out water, and the remaining water is removed through evaporation. Finally, the dry paper is compressed, coated, or impregnated, depending on the requirements.
Modern paper machines, like the Fourdrinier machine, have a headbox for distributing stock, a wire mesh for filtration, a press section for water removal, and a dryer section with steam-heated cylinders for evaporation. These machines can produce large quantities of paper at high speeds.
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What are some common uses of paper?
Paper is a versatile material with a wide array of uses due to its varied properties.
Common applications:
* Drawing and art Since the 15th century, paper has been the most popular surface for drawing. Different types of paper are used for different drawing mediums.
* Wrapping and packaging Kraft paper, known for its strength, is used extensively for making paper bags and multiwall sacks for shipping materials.
* Printing and books Paper is a key component of books, magazines, catalogs, and directories. Different finishes and coatings are applied for various printing needs, from simple line etchings to fine-screen halftones.
* Recycling Paper is a common material that can be recycled. Old newspapers and mixed paper can be reused to create new paper products.
* Paperboard Paperboard is used for food containers, boxes, and shipping containers.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How can paper be recycled or reused?
Paper is highly recyclable and reusable through several methods. After sorting, wastepaper can be repulped to create new paper products. Newsprint and cardboard can be recycled into similar materials, while other paper types can become boxboard, tissues, and towels. Paper intended for printing requires de-inking, often with caustic soda, and sometimes bleaching before being pressed into sheets.
Recycling paper reduces the need for virgin fiber, addressing solid waste disposal. Facilities use pulpers with agitator blades, hot water, and chemicals to separate and disperse the fibers. Furthermore, recycling paper helps save trees and supports the paper-making process.
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How does making and using paper affect the environment?
Paper production relies on trees; cutting them down can lead to deforestation, which has significant environmental effects. Forests play a role in sequestering carbon, so deforestation contributes to climate change because the carbon stored in the trees is released into the atmosphere as carbon dioxide, a greenhouse gas. Deforestation can also cause habitat loss, soil erosion, and air pollution.
Recycling efforts can reduce the environmental impact of paper use by decreasing the demand for virgin wood pulp. Recycling also saves energy and water, and it reduces the amount of waste that goes to landfills.
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paper, matted or felted sheet, usually made of cellulose fibres, formed on a wire screen from water suspension.
A brief treatment of paper follows. For full treatment, see papermaking.
Origin and development
Although pressed strips of the papyrus plant had been used to make writing material since the time of the ancient Egyptians, the origins of paper and papermaking can be traced to China. The oldest fragment of paper—a map recovered from a tomb in Fangmatan, Gansu Province, in 1986—dates to the second century BCE. The first records detailing a formal papermaking process, however, appeared in China in about ad 105. Paper and papermaking reached Central Asia by 751 and Baghdad by 793, and by the 14th century there were paper mills in several parts of Europe. The invention of the printing press in about 1450 greatly increased the demand for paper, and at the beginning of the 19th century wood and other vegetable pulps began to replace rags as the principal source of fibre for papermaking.
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Before 1798, Nicholas-Louis Robert constructed the first paper-making machine. Using a moving screen belt, paper was made one sheet at a time by dipping a frame or mold with a screen bottom into a vat of pulp. A few years later the brothers Henry and Sealy Fourdrinier improved Robert’s machine, and in 1809 John Dickinson invented the first cylinder machine.
Although almost all steps in papermaking have become highly mechanized, the basic process has remained essentially unchanged. First, the fibres are separated and wetted to produce the paper pulp, or stock. The pulp is then filtered on a woven screen to form a sheet of fibre, which is pressed and compacted to squeeze out most of the water. The remaining water is removed by evaporation, and the dry sheet is further compressed and, depending upon the intended use, coated or impregnated with other substances.
Types
Differences among the grades and types of paper are determined by several factors: the type of fibre used; the preparation of the pulp, either by mechanical (groundwood) or chemical (primarily sulfite, soda, or sulfate) methods, or by a combination of the two; by the addition of other materials to the pulp, among the most common being bleach or colouring and sizing, the latter to retard penetration by ink; by conditions under which the sheet is formed, including its weight; and by the physical or chemical treatments applied to the finished sheet.
Although wood has become the major source of fibre for papermaking, rag fibres are still used for paper of maximum strength, durability, and permanence. Recycled wastepaper (including newsprint) and paperboard are also important sources. Other fibres used include straw, bagasse (residue from crushed sugarcane), esparto, bamboo, flax, hemp, jute, and kenaf. Some paper, particularly specialty items, is made from synthetic fibres.
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Weight or substance per unit area, called basis weight, is measured in reams (now commonly 500 sheets). Paper is also measured by caliper (thickness) and density. The strength and durability of paper is determined by factors such as the strength and length of the fibres, as well as their bonding ability, and the formation and structure of the sheet. The optical properties of paper include its brightness, colour, opacity, and gloss. Among the most important paper grades are bond, book, bristol, groundwood and newsprint, kraft, paperboard, and sanitary.