Further additives
Raw paper that contains only pressed and dried pulp is very absorbent (for example, blotting paper), and does not provide a good surface upon which to write or print. Thus, a huge variety of additives are employed to add desired properties to the paper. These are applied in a coating called the size.
Sizing agents are often polymers designed to provide a better printing surface. Starches are very commonly used, as is PVA, but there as many types of polymer employed as there are types of paper.
Sizing agents can also improve the printing surface by smoothing it. The texture of raw paper is rough, and so to achieve greater smoothness, sizing agents such as clay are used. Smooth, matte finish papers such as magazine paper (for the inside pages) are made in this way. The glossy effect (for example on the covers of fashion magazines) is achieved at the end of the printing process, by adding a clear layer (like varnish) over the printing, and so is not a property of the paper.
Other additives are employed to enhance various properties of the paper, the most common of which are optical brighteners.
Drying
The paper may actually be dried several times during its manufacture (dry paper is much stronger than wet, so it is best to keep the paper dry to prevent it breaking and stopping the production line).
Applications
- to write or print on: the piece of paper becomes a document; this may be for keeping a record (or in the case of printing from a computer or copying from another paper: an additional record) and for communication; see also reading. Also a paper may represent a value:
In such cases making a copy that can not easily be distinguished from the original should be very difficult, to avoid abuse, see counterfeit.
- Official documents and private statements that are run through a computer are placed in individual letters by a "bursting machine." (right)
- Printed papers can be bound etc. to form a book, brochure, magazine, newspaper, etc.; a dysphemism for such an edition is "dead tree edition", as opposed to alternatives such as a file on hard disk (locally or accessed remotely through internet), CD-ROM, diskette, etc.
- A computer file can be converted to a paper document by printing, using a computer printer, the converse can be done by scanning, possibly followed by OCR.
History
A word paper comes from ancient Egyptian writing material called papyrus, which was woven from reedss. It was produced as early as 3000 BC Egypt, and then in ancient Greece and Rome.
Eventually, parchment or vellum, made of processed sheep or calfskins, replaced papyrus. In China, documents were ordinarily written on bamboo, making them very heavy and awkward to transport. Silk was sometimes used, but was usually too expensive to consider. Most of the above materials were rare and costly.
The modern method of papermaking was created by Chinese court official Ts'ai Lun in AD 105; he developed a method to make paper out of cotton rags. It spread slowly outside of China: other East Asian cultures, even after seeing paper, could not figure out how to make it themselves; instruction in the manufacturing process was required, and the Chinese were reluctant to share their secrets. The technology was first exported to Japan in 610, where fibres (called bast) from the mulberry tree were used. After commercial trades and the defeat of the Chinese in the Battle of Talas, the invention spread to the Middle East, where it was adopted by the Indians and subsequently by the Italians in about the 13th century. They used hemp and linen rags.
Some historians speculate that paper was the key element in global cultural advancement. According to this theory, Chinese culture was less developed than the West's in ancient times because bamboo was a clumsier writing material than papyrus; Chinese culture advanced during the Tang Dynasty and preceding centuries due to the invention of paper; and Europe advanced during the Renaissance due to the introduction of paper and the printing press.
Paper remained a luxury item through the centuries, until the advent of steam-driven paper making machines in the 19th century, which could make paper with fibres from wood pulp. Although older machines predated it, the Fourdrinier paper making machine became the basis for most modern papermaking. Together with the invention of the practical fountain pen and the mass produced pencil of the same period, and in conjunction with the advent of the steam driven rotary printing press, wood based paper caused a major transformation of the 19th century economy and society in industrialized countries. Before this era a book or a newspaper was a rare luxury object and illiteracy was the norm for the majority. With the gradual introduction of cheap paper, schoolbooks, fiction, non-fiction, and newspapers became slowly available to nearly all the members of an industrial society. Cheap wood based paper also meant that keeping personal diaries or writing letters ceased to be reserved to a privileged few in those same societies. The office worker or the white-collar worker was slowly born of this transformation, which can be considered as a part of the industrial revolution.
Unfortunately, the original wood-based paper was more acidic and more prone to disintegrate over time. Documents written on more expensive rag paper were more stable. The majority of modern book publishers now use acid-free paper.
The pulp and paper industry has been accused of being instrumental in forest destruction. Several major Asian producers, for example, with strong connections to their respective Governments and bureaucracy have been systematically stripping rainforest for many years. Often the logs are transhipped to other countries to disguise the damaging trade.
The Indonesian, Malaysian, Cambodian, Amazon rainforests are currently being subject to some of the worst excesses of environmental vandalism.
The processes by which paper is rendered white, in most cases, is also a source of concern. Many rivers have been badly damaged by the discharges from mills processing the wood pulp. These concerns are not merely side issues but rather display the comprehensive problems that occur when production dominates thinking. As in many problems over the years the mistaken belief is, and has traditionally been, that nature can cope. The short answer now is that nature cannot and increasingly the state of the ecosystems has been rendered such that the position has, and is becoming, terminal. The flow-on effect compounds and already disastrous position as in (for example) water quality.
External links
See also
cardboard, illegal logging.
ISO 216, newsprint, paper sizes, paper mill, paper recycling, stationery, washi, substrate (printing)
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