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[[Image:ManilaPaper.jpg|thumb|A stack of paper]]
'''Paper''' is thin material mainly used for writing upon, printing upon or packaging. It is produced by the amalgamation of [[fiber]]s, typically vegetable fibers composed of [[cellulose]], which are subsequently held together by [[hydrogen bond]]ing. While the fibers are usually natural in origin, a wide variety of synthetic fibers, such as polypropylene and polyethylene, may be incorporated into paper as a way of imparting desirable physical properties. The most common source of these kinds of fibers is [[wood pulp]] from [[pulpwood]] trees. [[fiber crop|Vegetable fiber]] materials such as [[cotton]], [[hemp]], [[linen]], and [[rice]] are also used.

==History==

====Papyrus and parchment====

Outside of Egypt, [[parchment]] or [[vellum]], made of processed [[sheep]]skin or [[calf]]skin, replaced papyrus as the papyrus plant requires subtropical conditions to grow.

In America, archaeological evidence indicates that a similar paper writing material was invented by the Mayans no later than the 5th century AD.<ref>[http://www.mathcs.duq.edu/~tobin/maya/ The Construction of the Codex In Classic- and post classic-Period Maya Civilization] Maya Codex and Paper Making</ref> Called [[amatory|''amatl'']], it was in widespread use among Mesoamerican cultures until the Spanish conquest. The paper is created by boiling and pounding the inner bark of trees, until the material becomes suitable for art and writing.

==== Early papermaking in China ====

[[Image:Jingangjing.jpg|thumb|rigt|The world's earliest known printed book (using [[woodblock printing]]), the [[Diamond Sutra]] of AD 868, shows the widespread availability and practicality of paper in China.]]
'''[[Papermaking]]''' is considered to be one of the ''[[Four Great Inventions of Ancient China]]'', since the first papermaking process was developed in China during the early 2nd century. During the [[Shang Dynasty|Shang]] ([[1600 BC]]-[[1050 BC]]) and [[Zhou Dynasty|Zhou]] ([[1050 BC]]-[[256 BC]]) dynasties of [[ancient China]], documents were ordinarily written on bone or [[bamboo]] (on tablets or on bamboo strips sewn and rolled together into scrolls), making them very heavy and awkward to transport. The light material of [[silk]] was sometimes used, but was normally too expensive to consider. While the [[Han Dynasty]] [[China|Chinese]] court official [[Cai Lun]] is widely regarded to have invented the modern method of papermaking (inspired from wasps and bees) from [[wood pulp]] in AD 105, the discovery of specimens bearing written [[Chinese character]]s in [[2006]] at north-east China's [[Gansu]] province suggest that paper was in use by the ancient Chinese military more than 100 years before Cai in 8 BC. [http://news.xinhuanet.com/english/2006-08/08/content_4937457.htm] Archeologically however, true paper without writing has been excavated in China dating to the reign of [[Emperor Wu of Han]] from the [[2nd century BC]], used for purposes of wrapping or padding protection for delicate bronze mirrors.<ref name="needham volume 4 122">Needham, Volume 4, 122.</ref> It was also used for safety, such as the padding of poisonous 'medicine' as mentioned in the official history of the period.<ref name="needham volume 4 122"/> Although paper used for writing became widespread by the 3rd century,<ref name="needham volume 4 1">Needham, Volume 4, 1.</ref> paper continued to be used for wrapping (and other) purposes.

[[Toilet paper]] was used in China by at least the 6th century AD.<ref name="needham volume 4 123">Needham, Volume 4, 123.</ref> In AD 589, the Chinese scholar-official [[Yan Zhitui]] ([[531]]-[[591]] AD) once wrote: "Paper on which there are quotations or commentaries from [[Five Classics]] or the names of [[sage]]s, I dare not use for toilet purposes".<ref name="needham volume 4 123"/> An [[Arab]] traveler to China once wrote of the curious Chinese tradition of toilet paper in AD 851, writing: "They (the Chinese) are not careful about cleanliness, and they do not wash themselves with water when they have done their necessities; but they only wipe themselves with paper".<ref name="needham volume 4 123"/> Toilet paper continued to be a valued necessity in China, since it was during the [[Hongwu Emperor]]'s reign in AD 1393 that the Bureau of Imperial Supplies (Bao Chao Si) manufactured 720,000 sheets of toilet paper for the entire court (produced of the cheap rice-straw paper).<ref name="needham volume 4 123"/> For the emperor's family alone, 15,000 special sheets of paper were made, in light yellow tint and even [[perfume]]d.<ref name="needham volume 4 123"/> Even at the beginning of the 14th century, during the middle of the [[Yuan Dynasty]], the amount of toilet paper manufactured for modern-day [[Zhejiang]] province alone amounted to ten million packages holding 1000 to 10000 sheets of toilet paper each.<ref name="needham volume 4 123"/>

During the [[Tang Dynasty]] (AD [[618]]-[[907]]) paper was folded and sewn into square bags to preserve the flavor of [[tea]].<ref name="needham volume 4 122"/> During the same period, it was written that tea was served from baskets with multi-colored paper cups and paper napkins of different size and shape.<ref name="needham volume 4 122"/> During the Chinese [[Song Dynasty]] (AD [[960]]-[[1279]]) not only did the government produce the world's first known paper-printed money, or [[banknote]] (''see [[Jiaozi (currency)|Jiaozi]] and [[Huizi]]''), but paper money bestowed as gifts to deserving government officials were wrapped in special paper [[envelope]]s.<ref name="needham volume 4 123"/>

Paper spread slowly outside of China; other [[East Asia]]n cultures, even after seeing paper, could not make it themselves. Instruction in the manufacturing process was required, and the Chinese were reluctant to share their secrets. The paper was thin and translucent, not like modern western paper, and thus only written on one side. The technology was first transferred to [[Korea]] in [[604]] and then imported to [[Japan]] by Buddhist priests, around [[610]], where fibres (called ''[[Bast (biology)|bast]]'') from the [[mulberry]] tree were used.

==== Papermaking arrives in the Middle East ====

After further commercial trading and the defeat of the Chinese in the [[Battle of Talas]] in 751, the invention spread to the [[Middle East]].<ref name="meggs58">Meggs, Philip B. ''A History of Graphic Design.'' John Wiley & Sons, Inc. 1998. (pp 58) ISBN 0-471-291-98-6</ref> Production was started in [[Baghdad]], where the Arabs invented a method to make a thicker sheet of paper. The manufacture had spread to [[Damascus]] by the time of the [[First Crusade]] in 1096; but the wars interrupted production, and it split into two centers. [[Cairo]] continued with the thicker paper. Iran became the center of the thinner papers. It was also adopted in [[India]]. The first paper mill in Europe was in [[Spain]], at Xátiva (modern [[Valencia (autonomous community)|Valencia]]) in 1120. More mills appeared in [[Fabriano]] [[Italy]] in about the [[13th century]], as an import from [[Islamic Spain]]. They used [[hemp]] and [[linen]] rags as a source of fibre. The oldest known paper document in the West is the [[Mozarab]] [[Missal of Silos]] from the [[11th century]], probably written in the Islamic part of Spain. Paper is recorded as being manufactured in both [[Italy]] and [[Germany]] by 1400, just about the time when the [[woodcut]] [[printmaking]] technique was transferred from fabric to paper in the [[old master print]] and [[popular prints]].

Some historians{{Who|date=December 2007}} speculate that paper was a key element in cultural advancement. According to this theory, Chinese culture was less developed than the West in ancient times prior to the [[Han Dynasty]] because bamboo, while abundant, was a clumsier writing material than papyrus; Chinese culture advanced during the Han Dynasty and subsequent centuries due to the invention of paper; and Europe advanced during the [[Renaissance]] due to the introduction of paper and the [[printing press]].

==== Nineteenth Century advances in papermaking ====

Paper remained expensive, at least in book-sized quantities, 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 Machine|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. With the introduction of cheaper paper, schoolbooks, fiction, non-fiction, and newspapers became gradually available by 1900. Cheap wood based paper also meant that keeping personal diaries or writing letters became possible and so, by 1850, the [[clerk]], or writer, ceased to be a high-status job.

The original wood-based paper was more acidic and more prone to disintegrate over time, through processes known as [[slow fires]]. Documents written on more expensive rag paper were more stable. Mass-market paperback books still use these cheaper mechanical papers (see below), but book publishers can now use [[acid-free paper]] for [[hardback]] and [[trade paperback]] books.

==Papermaking==
{{main|Papermaking}}

====Chemical pulping====

The purpose of a chemical pulping process is to break down the chemical structure of [[lignin]] and render it soluble in the cooking liquor, so that it may be washed from the [[cellulose]] fibres. Because lignin holds the plant cells together, chemical pulping frees the fibres and makes pulp. The pulp must be [[bleaching of wood pulp|bleached]] to produce white paper for [[printing]], painting and [[writing]]. Chemical pulps tend to cost more than mechanical pulps, largely due to the low yield, 40-50% of the original wood. Since the process preserves fibre length, however, chemical pulps tend to make stronger paper. Another advantage of chemical pulping is that the majority of the heat and electricity needed to run the process is produced by burning the lignin removed during pulping. Some chemicals used in chemical pulping are also known to be carcinogenic. [http://www.epa.gov/ost/pulppaper/jd/fs2.pdf]

Papers made from chemical wood-based pulps are also unhelpfully known as ''woodfree'' papers.

The [[Kraft process]] is the most commonly practiced strategy for pulp manufacturing and produces especially strong, unbleached papers that can be used directly for bags and boxes but are often processed further, e.g. to make corrugated cardboard.

====Mechanical pulping====

There are two major mechanical pulps, thermomechanical pulp (TMP) and mechanical pulp. The latter is known in the USA as groundwood pulp. In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and fibreized between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and fibreized. Mechanical pulping does not remove the lignin, so the yield is very high, >95%, but also causes paper made from this pulp to yellow and become brittle over time. Mechanical pulps have rather short fibre lengths and produce weak paper. Although large amounts of electrical energy are required to produce mechanical pulp, it costs less than chemical pulp.

====Recycled paper====

[[Paper recycling]] processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen bonds in the paper can be broken and fibres separated again. Most recycled paper contains a proportion of virgin fibre in the interests of quality.

There are three main classifications of recycled fibre:.
* Mill Broke or Internal Mill Waste - this incorporates any substandard or grade-change paper made within the paper mill which then goes back into the manufacturing system to be repulped back into paper. Such out-of-specification paper is not sold and is therefore often not classified as genuine reclaimed recycled fibre. However, most paper mills have been recycling their own waste fibre for many years, long before recycling become popular.

* Preconsumer Waste - this is offcuts and processing waste, such as guillotine trims and envelope blank waste. This waste is generated outside the paper mill and could potentially go to landfill, and is a genuine recycled fibre source. Also includes deinked preconsumer (recycled material that has been printed but did not reach its intended end use, such as waste from printers and unsold publications). <ref>Natural Resource Defense Council [[http://www.nrdc.org/]]</ref>

* Postconsumer waste - this is fibre from paper which has been used for its intended end use and would include office waste, magazine papers and newsprint. As the vast majority of this paper has been printed (either digitally or by more conventional means such as litho or gravure), it will either be recycled as printed paper or go through a de-inking process first.

Recycled Papers can be made from 100% recycled materials or blended with virgin pulp.
Recycled papers are (generally) not as strong nor as bright as papers made from virgin pulp.

====Additives====

Besides the fibres, pulps may contain fillers such as chalk or china clay, which improve the characteristics of the paper for printing or writing. Additives for [[sizing]] purposes may be mixed into the pulp and/or applied to the paper web later in the manufacturing process. The purpose of sizing is to establish the correct level of surface absorbency to suit the ink or paint.

====Drying====

After the paper web is produced, the water must be removed from it by pressing and drying.

Pressing the sheet removes the water by force. Once the water is forced from the sheet, felt (not to be confused with the traditional [[felt]]) is used to collect the water. When making paper by hand, a blotter sheet is used.

Drying involves using air and or heat to remove water from the paper sheet. In the earliest days of papermaking this was done by hanging the paper sheets like laundry. In more modern times, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam-heated can dryer. These dryers can heat to temperatures above 200°F (93°C) and are used in long sequences of more than 40 cans. The heat produced by these can easily dry the paper to less than 6% moisture.

====Finishing====

The paper may then undergo [[sizing]] to alter its physical properties for use in various applications.

Paper at this point is ''uncoated''. ''Coated'' paper has a thin layer of material such as china clay applied to one or both sides in order to create a surface more suitable for high-resolution [[halftone]] screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by [[calender]]ing. Coated papers are divided into matt, semi-matt or silk, and gloss. Gloss papers give the highest [[optical density]] in the printed image.

The paper is then fed onto reels if it is to be used on web printing presses, or cut into sheets for other printing processes or other purposes. The fibres in the paper basically run in the machine direction. Sheets are usually cut "long-grain", i.e. with the grain parallel to the longer dimension of the sheet.

All paper produced by Fourdrinier-type machines is wove paper, i.e. the wire mesh that transports the web leaves a pattern that has the same density along the paper grain and across the grain. Textured finishes, [[Watermark|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.

Wove paper does not exhibit "laidlines", which are small regular lines left behind on paper when it was handmade in a mould made from rows of metal wires or bamboo. Laidlines are very close together. They run perpendicular to the "chainlines", which are further apart. Handmade paper similarly exhibits "deckle edges", or rough and feathery borders.<ref>"Document Doubles" in [http://www.collectionscanada.ca/forgery/002035-500-e.html Detecting the Truth: Fakes, Forgeries and Trickery], a virtual museum exhibition at Library and Archives Canada </ref>

==Applications==

[[Image:Paper cutter 1.jpg|thumb|left|180px|A [[Paper cutter]]]]
*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 (activity)|reading]].

Paper can be produced with a wide variety of properties, depending on its intended use.<ref>{{cite web|url=http://www.paperonweb.com/grade11.htm|title=Grades and uses of paper|accessdate=2007-10-12}}</ref>
*'''To represent a value:''' [[paper money]], [[bank note]], [[cheque]], [[security]] (see [[Security paper]]), [[voucher]] and [[ticket]]
*'''For entertainment:''' [[book]], [[magazine]], [[newspaper]], [[art]], [[zine]],
*'''For packaging:''' [[corrugated box]], [[paper bag]], [[envelope]], [[wrapping tissue]], [[Charta emporetica]] and [[wallpaper]]
*'''For cleaning:''' [[toilet paper]], [[handkerchief]]s, [[paper towel]]s, [[facial tissue]] and [[cat litter]]
*'''For construction:''' [[papier-mâché]], [[origami]], [[quilling]], Paper [[honeycomb]], used as a core material in [[composite material]]s, [[paper engineering]], [[construction paper]] and [[clothing]]
*'''Other uses:''' [[emery paper]], [[sandpaper]], [[blotting paper]], [[litmus paper]], [[universal indicator]] paper, [[paper chromatography]] and [[Capacitor]] [[Dielectric]]s ([[Permittivity]] 1.5 - 3)

==Types and weight==

[[Image:Coloured, textured craft card.jpg|thumb|right|250px|Card and paper stock for [[craft]] use comes in a wide variety of textures and colors.]]
Paper is often characterized by weight. The weight assigned to a paper is the weight of a ream, 500 sheets, of varying "basic sizes", before the paper is cut into the size it is sold to end customers. For example, a ream of 20 lb, 8½ x 11" paper weighs 5 pounds, because it has been cut from a larger sheet into four pieces. <ref> McKenzie, Bruce G., ''The Hammermill Guide to Desktop Publishing in Business'', p. 144, Hammermill Papers, 1989. </ref> In the United States, printing paper is generally 20 lb, 24 lb, or 32 lb at most. Cover stock is generally 68 lb, and 110 lb or more is considered card stock.

In Europe the weight is expressed in grammes per square metre (gsm or usually just g) of the paper. Printing paper is generally between 60g and 120g. Anything heavier than 160g is considered card. The weight of a ream with therefore depends on the dimensions of the paper; One ream of A4 (210mm x 297mm) size (approx 8.27" x 11.7") weighs 2.5 kilogrammes (approx 5.5 pounds).

The [[density]] of paper ranges from 250&nbsp;kg/m<sup>3</sup> (16 lb/ft<sup>3</sup>) for tissue paper to 1500&nbsp;kg/m<sup>3</sup> (94&nbsp;lb/ft<sup>3</sup>) for some speciality paper. Printing paper is about 800&nbsp;kg/m<sup>3</sup> (50&nbsp;lb/ft<sup>3</sup>).<ref>{{cite web|url=http://www.paperonweb.com/density.htm|title=Density of paper and paperboard|publisher=PaperOnWeb|accessdate=2007-10-31}}</ref>

{{col-begin}}
{{col-break}}
*[[Bank paper]]
*[[Bond paper]]
*[[Book paper]]
*[[Construction paper|Construction paper/sugar paper]]
*[[Cotton paper]]
*[[Electronic paper]]
*[[Fish paper]] ([[Vulcanized]] fibres for electrical insulation)
*[[Inkjet paper]]
*[[Kraft paper]]
*[[Laid paper]]
*[[Leather paper]]
*[[mummy paper]]

*[[Tyvek paper]]
*[[Paper towels]]
*[[Wallpaper]]
*[[Washi]]
*[[Wax paper]]
*[[Wet and Dry Paper]]
*[[Wove paper]]
*[[Coated paper]]: glossy and matt surface
{{col-end}}

==The future of paper==

Some manufacturers, notably [[AMD]], have started using a new, significantly more environmentally friendly alternative to expanded plastic packaging made out of paper, known commercially as [[paperfoam]]. The packaging has very similar mechanical properties to some expanded plastic packaging, but is biodegradable and can also be recycled with ordinary paper. [http://www.paperfoam.com/]

With increasing environmental concerns about synthetic coatings (such as [[PFOA]]) and the higher prices of hydrocarbon based petrochemicals, there is a focus on [[zein]] (corn protein) as a coating for paper in high grease applications such as popcorn bags. [http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=WO2006002346&F=0]

Besides paperfoam, paper made from [[Rock (geology)|rocks]] rather than trees is also emerging as a more [[ecological]] alternative to regular paper made from trees or other alternatives as paperfoam.<ref>[http://www.treehugger.com/files/2006/02/rock_paperwater.php Rock paper emerging as ecological alternative]</ref> This [[Rock paper]] is available from companies as [[ViaStone]] and [[John Su]].<ref>[http://www.treehugger.com/files/2006/02/rock_paperwater.php John Su distributing rock paper]</ref><ref>[http://www.treehugger.com/files/2006/08/viastone_biodeg_2.php. ViaStone distributing rock paper]</ref>

Invisible paper is being developed by Gaskell Industries Ltd., to be used as a substitute to more visible alternatives.

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

==Notes==

{{Reflist}}

==References==

*Needham, Joseph (1986). ''Science and Civilization in China: Volume 5, Chemicals and Chemical Technology, Part 1, Paper and Printing''. New York: Cambridge University Press, 1985. (also published in Taipei: Caves Books, Ltd., 1986.)
::also referred to as:
*Tsien, Tsuen-Hsuin, '"Paper and Printing," vol. 5 part 1 of Needham, Joseph ''Science and Civilization in China:''. Cambridge University Press, 1986. ISBN 0521086906. (also published in Taipei: Caves Books, Ltd., 1986.)
*"Document Doubles" in [http://www.collectionscanada.ca/forgery/ Detecting the Truth: Fakes, Forgeries and Trickery], a virtual museum exhibition at Library and Archives Canada

==See also==

*[[Arches paper]]
*[[Buckypaper]]
*[[Graphene Oxide Paper]]
*[[Paperclip]]
*[[Paper recycling]]
*[[Paper size]]

==External links==

{{commonscat|Paper}}
*[http://www.tappi.org TAPPI] Technical Association of the Pulp and Paper Industry
*[http://www.straightdope.com/mailbag/mpapermaking.html ''How is paper made?''] at The [[Straight Dope]], [[22 November]] [[2005]]
*[http://internationalpaper.com/Our%20Company/Learning%20Center/How%20Paper%20Is%20Made.html How Paper Is Made]
*[http://www.gpo.gov/acquisition/paperspecs.htm United States Government Printing Office: Government Paper Specification Standards]


[[Category:Writing media]]
[[Category:Materials]]
[[Category:Paper]]
[[Category:Stationery]]
[[Category:Art materials]]
[[Category:Paper art]]
[[Category:Recyclable materials]]
[[Category:Traditional Chinese objects]]
[[Category:Packaging materials]]

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Revision as of 21:00, 10 March 2008

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