Paper

Paper

Overview
Paper is a thin material mainly used for writing
Writing
Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and non-symbolic preservation of language via non-textual media, such as magnetic tape audio.Writing most likely...

 upon, printing
Printing
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

 upon, drawing
Drawing
Drawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, markers, styluses, and various metals .An artist who...

 or for packaging. It is produced by pressing together moist fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....

s, typically cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 pulp derived from wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, rags or grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

es, and drying them into flexible sheets.

Paper is a versatile material with many uses. Whilst the most common is for writing and printing upon, it is also widely used as a packaging material, in many cleaning products, in a number of industrial and construction processes, and even as a food ingredient – particularly in Asian cultures.

Paper, and the pulp papermaking process, was said to be developed in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 during the early 2nd century AD by the Han
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...

 court eunuch Cai Lun
Cai Lun
Cai Lun , courtesy name Jingzhong , was a Chinese eunuch. He is traditionally regarded as the inventor of paper and the papermaking process, in forms recognizable in modern times as paper...

, although the earliest archaeological fragments of paper derive from the 2nd century BC in China.


The oldest known archaeological fragments of the immediate precursor to modern paper date to 2nd century BC China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

.
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Encyclopedia
Paper is a thin material mainly used for writing
Writing
Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and non-symbolic preservation of language via non-textual media, such as magnetic tape audio.Writing most likely...

 upon, printing
Printing
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

 upon, drawing
Drawing
Drawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, markers, styluses, and various metals .An artist who...

 or for packaging. It is produced by pressing together moist fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....

s, typically cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 pulp derived from wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, rags or grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

es, and drying them into flexible sheets.

Paper is a versatile material with many uses. Whilst the most common is for writing and printing upon, it is also widely used as a packaging material, in many cleaning products, in a number of industrial and construction processes, and even as a food ingredient – particularly in Asian cultures.

Paper, and the pulp papermaking process, was said to be developed in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 during the early 2nd century AD by the Han
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...

 court eunuch Cai Lun
Cai Lun
Cai Lun , courtesy name Jingzhong , was a Chinese eunuch. He is traditionally regarded as the inventor of paper and the papermaking process, in forms recognizable in modern times as paper...

, although the earliest archaeological fragments of paper derive from the 2nd century BC in China.

History



The oldest known archaeological fragments of the immediate precursor to modern paper date to 2nd century BC China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. Papermaking
Papermaking
Papermaking is the process of making paper, a substance which is used universally today for writing and packaging.In papermaking a dilute suspension of fibres in water is drained through a screen, so that a mat of randomly interwoven fibres is laid down. Water is removed from this mat of fibres by...

 is considered one of the Four Great Inventions of China, and the pulp papermaking process is ascribed to Cai Lun
Cai Lun
Cai Lun , courtesy name Jingzhong , was a Chinese eunuch. He is traditionally regarded as the inventor of paper and the papermaking process, in forms recognizable in modern times as paper...

, a 2nd century AD Han
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...

 court eunuch. With paper an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age
Golden Age
The term Golden Age comes from Greek mythology and legend and refers to the first in a sequence of four or five Ages of Man, in which the Golden Age is first, followed in sequence, by the Silver, Bronze, and Iron Ages, and then the present, a period of decline...

.

Paper spread from China through the Islamic world
Muslim world
The term Muslim world has several meanings. In a religious sense, it refers to those who adhere to the teachings of Islam, referred to as Muslims. In a cultural sense, it refers to Islamic civilization, inclusive of non-Muslims living in that civilization...

 to medieval Europe in the 13th century, where the first water-powered paper mill
Paper mill
A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags and other ingredients using a Fourdrinier machine or other type of paper machine.- History :...

s were built. In the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts. In 1844, Canadian inventor Charles Fenerty
Charles Fenerty
Charles Fenerty , is a Canadian inventor who invented the wood pulp process for papermaking, which was first adapted into the production of newsprint. Fenerty was also a poet...

 and German F.G. Keller independently developed processes for pulping wood fibers.

Etymology



The word "paper" is etymologically derived from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 papyrus, which comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 πάπυρος (papuros), the word for the Cyperus papyrus
Cyperus papyrus
Cyperus papyrus is a monocot belonging to the sedge family Cyperaceae. It is a herbaceous perennial native to Africa, and forms tall stands of reed-like swamp vegetation in shallow water....

plant. Papyrus
Papyrus
Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt....

 is a thick, paper-like material produced from the pith of the Cyperus papyrus plant which was used in ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

 and other Mediterranean
History of the Mediterranean region
The history of the Mediterranean region is the history of the interaction of the cultures and people of the lands surrounding the Mediterranean Sea —the central superhighway of transport, trade and cultural exchange between diverse peoples...

 cultures for writing
History of writing
The history of writing records the development of expressing language by letters or other marks. In the history of how systems of representation of language through graphic means have evolved in different human civilizations, more complete writing systems were preceded by proto-writing, systems of...

 before the introduction of paper into the Middle East and Europe. Although paper is etymologically derived from papyrus, the two are produced very differently and the development of modern paper is separate from the development of papyrus. Papyrus is a "lamination of natural plants, while paper is manufactured from fibres whose properties have been changed by maceration or disintegration.

Chemical pulping


The purpose of a chemical pulping process is to break down the chemical structure of lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

 and render it soluble in the cooking liquor, so that it may be washed from the cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 fibers. Because lignin holds the plant cells together, chemical pulping frees the fibres and makes pulp. The pulp can also be bleached
Bleaching of wood pulp
Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. The main use of wood pulp is to make paper where whiteness is an important characteristic...

 to produce white paper for printing
Printing
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

, painting
Painting
Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

 and writing
Writing
Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and non-symbolic preservation of language via non-textual media, such as magnetic tape audio.Writing most likely...

. 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
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 needed to run the process is produced by burning the lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

 removed during pulping.

Paper made from chemical pulps are also known as wood-free paper
Wood-free paper
Wood-free paper is paper created exclusively from chemical pulp rather than mechanical pulp. Chemical pulp is normally made from pulpwood, but is not considered wood as most of the lignin is removed and separated from the cellulose fibers during processing, whereas mechanical pulp retains most of...

s. Not to be confused with tree-free paper
Tree-free paper
Tree-free paper or tree-free newsprint describes an alternative to wood-pulp paper by its raw material composition. It is claimed to be more eco-friendly considering the product's entire life cycle.Sources of fibre for tree-free paper include:...

.

The kraft process
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...

 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, thermo mechanical pulp (TMP) and groundwood pulp (GW). In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and made into fibres between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and made into fibres. Mechanical pulping does not remove the lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

, 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.

Deinked pulp


Paper recycling
Paper recycling
Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. Mill broke is paper trimmings and other paper...

 processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 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. Generally deinked pulp is of the same quality or lower than the collected paper it was made from.

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 re-pulped 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 de-inked preconsumer (recycled material that has been printed but did not reach its intended end use, such as waste from printers and unsold publications).
  • 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 lithography or rotogravure), it will either be recycled as printed paper or go through a deinking process first.


Recycled papers can be made from 100% recycled materials or blended with virgin pulp. They 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
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

 or china clay, which improve the characteristics of the paper for printing or writing. Additives for sizing
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

 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.

Producing paper


The pulp
Pulp (paper)
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...

 is feed to a paper machine where it is formed as a paper web and the water is 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
Felt
Felt is a non-woven cloth that is produced by matting, condensing and pressing woollen fibres. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any colour, and made into any shape or size....

) 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 (93.3 °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
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

 to alter its physical properties for use in various applications.

Paper at this point is uncoated. Coated paper
Coated paper
Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...

 has a thin layer of material such as calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone
Halftone
Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size, in shape or in spacing...

 screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by calender
Calender
The calender is a series of hard pressure rollers used to form or smooth a sheet of material. In a principal application, the calender is located at the end of a papermaking process . Those that are used separate from the process are also called supercalenders...

ing. Coated papers are divided into matte, semi-matte 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 paper machines as the Fourdrinier Machine
Fourdrinier machine
This article contains a glossary section at the end.Most modern papermaking machines are based on the principles of the Fourdrinier Machine. It has been used in some variation since its inception...

 are 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
Watermark
A watermark is a recognizable image or pattern in paper that appears as various shades of lightness/darkness when viewed by transmitted light , caused by thickness or density variations in the paper...

s 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.

Applications


Paper can be produced with a wide variety of properties, depending on its intended use.
  • For representing value: paper money
    Paper Money
    Paper Money is the second album by the band Montrose. It was released in 1974 and was the band's last album to feature Sammy Hagar as lead vocalist.-History:...

    , bank note, cheque
    Cheque
    A cheque is a document/instrument See the negotiable cow—itself a fictional story—for discussions of cheques written on unusual surfaces. that orders a payment of money from a bank account...

    , security
    Security
    Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection are structures and processes that provide or improve security as a condition. The Institute for Security and Open Methodologies in the OSSTMM 3 defines security as "a form of protection...

     (see security paper
    Security paper
    Security paper is paper which incorporates features which can act to identify or authenticate a document as original or features which demonstrate tamper evidence when fraud is attempted, e.g., to remove or alter print such as amounts or signatures on a cheque...

    ), voucher
    Voucher
    A voucher is a bond which is worth a certain monetary value and which may be spent only for specific reasons or on specific goods. Examples include housing, travel, and food vouchers...

     and ticket
    Ticket (admission)
    A ticket is a voucher that indicates that one has paid for admission to an event or establishment such as a theatre, movie theater, amusement park, zoo, museum, concert, or other attraction, or permission to travel on a vehicle such as an airliner, train, bus, or boat, typically because one has...

  • For storing information
    Data storage device
    thumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....

    : book
    Book
    A book is a set or collection of written, printed, illustrated, or blank sheets, made of hot lava, paper, parchment, or other materials, usually fastened together to hinge at one side. A single sheet within a book is called a leaf or leaflet, and each side of a leaf is called a page...

    , notebook
    Notebook
    A notebook is a book or binder composed of pages of notes, often ruled, made out of paper, used for purposes including recording notes or memoranda, writing, drawing, and scrapbooking....

    , magazine
    Magazine
    Magazines, periodicals, glossies or serials are publications, generally published on a regular schedule, containing a variety of articles. They are generally financed by advertising, by a purchase price, by pre-paid magazine subscriptions, or all three...

    , newspaper
    Newspaper
    A newspaper is a scheduled publication containing news of current events, informative articles, diverse features and advertising. It usually is printed on relatively inexpensive, low-grade paper such as newsprint. By 2007, there were 6580 daily newspapers in the world selling 395 million copies a...

    , art
    Art
    Art is the product or process of deliberately arranging items in a way that influences and affects one or more of the senses, emotions, and intellect....

    , zine
    Zine
    A zine is most commonly a small circulation publication of original or appropriated texts and images. More broadly, the term encompasses any self-published work of minority interest usually reproduced via photocopier....

    , letter
  • For personal use: diary
    Diary
    A diary is a record with discrete entries arranged by date reporting on what has happened over the course of a day or other period. A personal diary may include a person's experiences, and/or thoughts or feelings, including comment on current events outside the writer's direct experience. Someone...

    , note to remind oneself, etc.; for temporary personal use: scratch paper
  • For communication
    Communication
    Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...

    :
    between individuals and/or groups of people.
  • For packaging: corrugated box, paper bag
    Paper bag
    A paper bag or paper sack is a preformed container made of paper, usually with an opening on one side. It can be one layer of paper or multiple layers of paper and other flexible materials. A bag is used for packaging and/or carrying items....

    , envelope
    Envelope
    An envelope is a common packaging item, usually made of thin flat material. It is designed to contain a flat object, such as a letter or card....

    , wrapping tissue
    Wrapping tissue
    Wrapping tissue is a translucent, thin tissue paper used for wrapping and cushioning items.Wrapping tissue is usually found in single sheets or sheet collections of 25, 40, or 50...

    , Charta emporetica
    Charta emporetica
    In pharmacy, etc, charta emporetica was a kind of paper made very soft and porous, used as a filter. It was also used as packing paper....

     and wallpaper
    Wallpaper
    Wallpaper is a kind of material used to cover and decorate the interior walls of homes, offices, and other buildings; it is one aspect of interior decoration. It is usually sold in rolls and is put onto a wall using wallpaper paste...

  • For cleaning: toilet paper
    Toilet paper
    Toilet paper is a soft paper product used to maintain personal hygiene after human defecation or urination. However, it can also be used for other purposes such as blowing one's nose when one has a cold or absorbing common spills around the house, although paper towels are more used for the latter...

    , handkerchief
    Handkerchief
    A handkerchief , also called a handkercher or hanky, is a form of a kerchief, typically a hemmed square of thin fabric that can be carried in the pocket or purse, and which is intended for personal hygiene purposes such as wiping one's hands or face, or blowing one's nose...

    s, paper towel
    Paper towel
    A paper towel is an absorbent textile made from paper instead of cloth. Unlike cloth towels, paper towels are disposable and intended to be used only once. Paper towels soak up water because they are loosely woven which enables water to travel between them, even against gravity...

    s, facial tissue
    Facial tissue
    Facial tissue and paper handkerchief refers to a class of soft, absorbent, disposable papers that is suitable for use on the face. They are disposable alternatives for cloth handkerchiefs...

     and cat litter
  • For construction: papier-mâché
    Papier-mâché
    Papier-mâché , alternatively, paper-mache, is a composite material consisting of paper pieces or pulp, sometimes reinforced with textiles, bound with an adhesive, such as glue, starch, or wallpaper paste....

    , origami
    Origami
    is the traditional Japanese art of paper folding, which started in the 17th century AD at the latest and was popularized outside Japan in the mid-1900s. It has since then evolved into a modern art form...

    , paper plane
    Paper plane
    A paper plane, paper aeroplane , paper airplane , paper glider, paper dart or dart is a toy aircraft, usually a glider made out of paper or paperboard; the practice of constructing paper planes is sometimes referred to as aerogami , after origami, the Japanese art of paper folding.-History:The...

    s, quilling
    Quilling
    Quilling or paper filigree is an art form that involves the use of strips of paper that are rolled, shaped, and glued together to create decorative designs. The paper is wound around a quill to create a basic coil shape...

    , paper honeycomb
    Paper honeycomb
    Paper honeycomb is a building and packing material. One of the most commons uses of paper honeycomb is for standard doors inside houses. Typically a layer of fiberglass and then the enforced paper made into honeycomb shapes and then another layer of fiberglass...

    , used as a core material in composite material
    Composite material
    Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

    s, paper engineering
    Paper engineering
    For other uses, see Paper foldingPaper engineering is a branch of engineering that deals with the usage of physical science and life sciences in conjunction with mathematics as applied to the converting of renewable raw materials into useful and valuable products...

    , construction paper
    Construction paper
    Construction paper is a tough, coarse, colored paper. The texture is slightly rough, and the surface is unfinished. Due to the source material, small particles are visible on the paper’s surface. It is used for projects or crafts....

     and paper clothing
    Paper clothing
    Paper clothing, in the form of women's dresses and other clothes made from disposable cellulose fabric, was a short-lived fashion novelty item in the 1960s United States....

  • For other uses: emery paper
    Emery paper
    Emery paper is a type of paper that can be used for sanding down hard and rough surfaces.It can also be used for resistant technology purposes to give a smooth, shiny finish to manufactured products and is often used in the finishing of high-end watch movements.Similar to sandpaper, it is made by...

    , sandpaper
    Sandpaper
    Sandpaper, also known as glasspaper, is a heavy paper with abrasive material attached to its surface.Sandpaper is part of the "coated abrasives" family of abrasive products. It is used to remove small amounts of material from surfaces, either to make them smoother , to remove a layer of material...

    , blotting paper
    Blotting paper
    Blotting paper is a highly absorbent type of paper or other material. It is used to absorb an excess of liquid substances from the surface of writing paper or objects. It is also commonly used as a beauty tool to absorb excess oil from the skin.-Manufacture:Blotting paper is made from different...

    , litmus paper, universal indicator
    Universal indicator
    A Universal indicator is a pH indicator composed of a blend of several compounds that exhibits several smooth colour changes over a pH value range from 1-14 to indicate the acidity or basicity of solutions. Although there are a number of commercially available universal pH indicators, most are a...

     paper, paper chromatography
    Paper chromatography
    Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be colored, especially pigments. This can also be used in secondary or primary colors in ink experiments. This method has been largely replaced by thin layer chromatography, however it...

    , electrical insulation paper
    Electrical insulation paper
    Electrical insulation papers are paper types that are used as electrical insulation in many applications due to pure cellulose having outstanding electrical properties...

     (see also dielectric
    Dielectric
    A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...

    and permittivity
    Permittivity
    In electromagnetism, absolute permittivity is the measure of the resistance that is encountered when forming an electric field in a medium. In other words, permittivity is a measure of how an electric field affects, and is affected by, a dielectric medium. The permittivity of a medium describes how...

    ) and filter paper
    Filter paper
    Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solids from liquids or air.-Properties:Filter paper comes in various porosities and grades depending on the applications it is meant for...


Types, thickness and weight




The thickness of paper is often measured by caliper, which is typically given in thousandths of an inch. Paper may be between 0.07 millimetre (0.00275590551181102 in) and 0.18 millimetre (0.00708661417322835 in) thick.

Paper is often characterized by weight. In the United States, 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, 8.5 by 11 in (215.9 by 279.4 mm) paper weighs 5 pounds, because it has been cut from a larger sheet into four pieces. 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
Card stock
Card stock, also called cover stock or pasteboard, is a paper stock that is thicker and more durable than normal writing or printing paper, but thinner and more flexible than other forms of paperboard. Card stock is often used for business cards, postcards, playing cards, catalog covers,...

.

In Europe, and other regions using the ISO 216
ISO 216
ISO 216 specifies international standard paper sizes used in most countries in the world today. It defines the "A" and "B" series of paper sizes, including A4, the most commonly available size...

 paper sizing system, the weight is expressed in grammes per square metre (g/m2 or usually just g) of the paper. Printing paper is generally between 60 g and 120 g. Anything heavier than 160 g is considered card. The weight of a ream therefore depends on the dimensions of the paper and its thickness.

Most commercial paper sold in North America is cut to standard paper sizes based on customary units and is defined by the length and width of a sheet of paper.

The ISO 216 system used in most other countries is based on the surface area of a sheet of paper, not on a sheet's width and length. It was first adopted in Germany in 1922 and generally spread as nations adopted the metric system. The largest standard size paper is A0 (A zero), measuring one square meter (approx. 1189x841 mm). Two sheets of A1, placed upright side by side fit exactly into one sheet of A0 laid on its side. Similarly, two sheets of A2 fit into one sheet of A1 and so forth. Common sizes used in the office and the home are A4 and A3 (A3 is the size of two A4 sheets).

The density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 of paper ranges from 250 kg/m3 for tissue paper to 1500 kg/m3 for some speciality paper. Printing paper is about 800 kg/m3.

Paper may be classified into seven categories:
  • Printing papers of wide variety.
  • Wrapping papers for the protection of goods and merchandise. This includes wax and kraft papers.
  • Writing paper suitable for stationary requirements. This includes ledger, bank, and bond paper.
  • Blotting papers containing little or no size.
  • Drawing papers usually with rough surfaces used by artists and designers, including cartridge paper.
  • Handmade papers including most decorative papers, Ingres papers, Japanese paper and tissues, all characterized by lack of grain direction.
  • Specialty papers including cigarette paper, toilet tissue, and other industrial papers.


Some paper types include:
  • Bank paper
    Bank paper
    Bank paper is a thin strong writing paper of less than 50g/m2 commonly used for typewriting and correspondence.Bank paper are also securities which banks instead of governments issue. See also Commercial paper, securities issued by corporations....

  • Banana paper
    Banana paper
    Banana paper is used in two different senses: to refer to a paper made from the bark of the banana plant, mainly used for artistic purposes, or paper made from banana fiber, obtained from an industrialized process, from the stem and the non-utilizable fruits...

  • Bond paper
    Bond paper
    Bond paper is a high quality durable writing paper similar to bank paper but having a weight greater than 50 g/m2. The name comes from it having originally been made for documents such as government bonds. It is now used for letterheads, other stationery and as paper for electronic printers...

  • Book paper
    Book paper
    A book paper is a paper which is designed specifically for the publication of printed books. Traditionally, book papers are off white or low white papers , are opaque to minimise the show through of text from one side of the page to the other and are made to tighter caliper or thickness...

  • Coated paper
    Coated paper
    Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...

    : glossy and matte surface
  • Construction paper/sugar paper
    Construction paper
    Construction paper is a tough, coarse, colored paper. The texture is slightly rough, and the surface is unfinished. Due to the source material, small particles are visible on the paper’s surface. It is used for projects or crafts....

  • Cotton paper
    Cotton paper
    Cotton paper is made from cotton linters or cotton from used cloths were the primary material source, hence the name rag paper. Cotton paper is superior in both strength and durability to wood pulp-based paper, which may contain high concentrations of acids.-Properties:Certain cotton fibre paper...

  • Electronic paper
    Electronic paper
    Electronic paper, e-paper and electronic ink are a range of display technology which are designed to mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat panel displays, electronic paper displays reflect light like ordinary paper...


  • Fish paper (vulcanized fibres for electrical insulation)
  • Inkjet paper
    Inkjet paper
    Inkjet paper is a special fine paper designed for inkjet printers, typically classified by its weight, brightness and smoothness, and sometimes by its opacity.-Manufacture:...

  • Kraft paper
    Kraft paper
    Kraft paper or kraft is paper or paperboard produced from chemical pulp produced in the kraft process.Pulp produced by the kraft process is stronger than that made by other pulping processes; acidic sulfite processes degrade cellulose more, leading to weaker fibers, and mechanical pulping...

  • Laid paper
    Laid paper
    Laid paper is a type of paper having a ribbed texture imparted by the manufacturing process. In the 19th century its use diminished as it was largely supplanted by wove paper...

  • Leather paper
  • Mummy paper
    Mummy paper
    Mummy paper is paper that is claimed to be made from the linen wrappings and other fibers from Egyptian mummies imported to America circa 1855...

  • Sandpaper
    Sandpaper
    Sandpaper, also known as glasspaper, is a heavy paper with abrasive material attached to its surface.Sandpaper is part of the "coated abrasives" family of abrasive products. It is used to remove small amounts of material from surfaces, either to make them smoother , to remove a layer of material...


  • Tyvek paper
  • Wallpaper
    Wallpaper
    Wallpaper is a kind of material used to cover and decorate the interior walls of homes, offices, and other buildings; it is one aspect of interior decoration. It is usually sold in rolls and is put onto a wall using wallpaper paste...

  • Washi
    Washi
    is a type of paper made in Japan. Washi is commonly made using fibers from the bark of the gampi tree, the mitsumata shrub , or the paper mulberry, but also can be made using bamboo, hemp, rice, and wheat...

  • Waterproof paper
    Waterproof paper
    Waterproof paper is good for extreme outdoor, marine, field use and general wet environments. Often designed especially for printing topographic maps...

  • Wax paper
    Wax paper
    Wax paper is a kind of paper that is made moisture proof through the application of wax....

  • Wove paper
    Wove paper
    Wove paper is a writing paper with a uniform surface, not ribbed or watermarked.The papermaking mould's wires run parallel to each other to produce laid paper, but they are woven together into a fine wire mesh for wove paper...

  • Xuan paper
    Xuan paper
    Xuan paper , or Shuen paper or rice paper, is a kind of paper originating in ancient China used for writing and painting...



Paper stability


Much of the early paper made from wood pulp contained significant amounts of alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...

, a variety of aluminium sulfate
Aluminium sulfate
Aluminium sulfate, alternatively spelt aluminum sulfate, aluminium sulphate, or aluminum sulphate; is a chemical compound with the formula Al23...

 salts that are significantly acidic. Alum was added to paper to assist in sizing
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

 the paper, making it somewhat water resistant so that inks did not "run" or spread uncontrollably. The early papermakers did not realize that the alum they added liberally to cure almost every problem encountered in making their product would eventually be detrimental. The cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 fibres which make up paper are hydrolyzed by acid, and the presence of alum would eventually degrade the fibres until the paper disintegrated in a process which has come to be known as "slow fire
Slow fires
A slow fire is a term used in library and information science to describe paper embrittlement resulting from acid decay. The term is taken from the title of Terry Sanders' 1987 film Slow Fires: On the preservation of the human record....

". Documents written on rag paper
Cotton paper
Cotton paper is made from cotton linters or cotton from used cloths were the primary material source, hence the name rag paper. Cotton paper is superior in both strength and durability to wood pulp-based paper, which may contain high concentrations of acids.-Properties:Certain cotton fibre paper...

 were significantly more stable. The use of non-acidic additives to make paper is becoming more prevalent and the stability of these papers is less of an issue.

Paper made from mechanical pulp contains significant amounts of lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

, a major component in wood. In the presence of light and oxygen lignin reacts to give yellow materials, which is why newsprint
Newsprint
Newsprint is a low-cost, non-archival paper most commonly used to print newspapers, and other publications and advertising material. It usually has an off-white cast and distinctive feel. It is designed for use in printing presses that employ a long web of paper rather than individual sheets of...

 and other mechanical paper yellows with age. Paper made from bleached
Bleaching of wood pulp
Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. The main use of wood pulp is to make paper where whiteness is an important characteristic...

 kraft
Kraft process
The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers...

 or sulfite
Sulfite process
The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites , depending on the pH...

 pulps does not contain significant amounts of lignin and is therefore better suited for books, documents and other applications where whiteness of the paper is essential.

It is important to note that just because a paper is made of wood pulp, does not necessarily mean it is any less durable than a rag paper. The factor that determines the ageing behavior of a paper is how it was manufactured, not the original source of the fibres. Furthermore, tests sponsored by the Library of Congress prove that all paper is at risk of acid decay, because cellulose itself produces formic, acetic, lactic and oxalic acids.

Mechanical pulping yields almost a tonne of pulp per tonne of dry wood used (which is why mechanical pulps are sometimes referred to as "high yield" pulps), which is about twice as much as chemical pulping. Consequently, paper made with mechanical pulps is often cheaper than that made with bleached chemical pulps. Mass-market paperback books and newspapers use these mechanical papers. Book publishers tend to use acid-free paper
Acid-free paper
Acid-free paper is paper that has a neutral or basic pH . It can be made from any cellulose fiber as long as the active acid pulp is eliminated during processing. It is also lignin and sulfur free...

, made from fully bleached chemical pulps for hardback and trade paperback books.

The future of paper


Some manufacturers 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.

With increasing environmental concerns about synthetic coatings (such as PFOA) and the higher prices of hydrocarbon based petrochemicals, there is a focus on zein
Zein
Zein is a class of prolamine protein found in maize. It is usually manufactured as a powder from corn gluten meal.-Commercial uses:Zein is one of the best understood plant proteins and has a variety of industrial and food uses...

 (corn protein) as a coating for paper in high grease applications such as popcorn bags.

Also, synthetics such as Tyvek
Tyvek
Tyvek is a brand of flashspun high-density polyethylene fibers, a synthetic material; the name is a registered trademark of DuPont. The material is very strong; it is difficult to tear but can easily be cut with scissors or a knife...

 and Teslin have been introduced as printing media as a more durable material than paper.

See also


  • Arches paper
    Arches paper
    Arches paper is a type of air-dried paper that is preferred amongst printers and watercolorists. It has a warm-white colour and can be found in hot-pressed, cold-pressed, and rough varieties. Arches paper is valued for its durability, and is still made today at the Arches paper mill in Lorraine,...

  • Buckypaper
    Buckypaper
    Buckypaper is a thin sheet made from an aggregate of carbon nanotubes. The nanotubes are approximately 50,000 times thinner than a human hair. Originally, it was fabricated as a way to handle carbon nanotubes, but it is also being studied and developed into applications by several research groups,...

  • Deinked pulp
  • Fiber crop
    Fiber crop
    Fiber crops are field crops grown for their fibers, which are traditionally used to make paper, cloth, or rope. The fibers may be chemically modified, like in viscose or cellophane...

  • Graphene oxide paper
    Graphene Oxide Paper
    Graphene oxide paper or graphite oxide paper is a composite material fabricated from graphite oxide.The material has exceptional stiffness and strength, due to the intrinsic strength of the two-dimensional graphene backbone and to its interwoven layer structure which distributes loads.The starting...

  • Origami
    Origami
    is the traditional Japanese art of paper folding, which started in the 17th century AD at the latest and was popularized outside Japan in the mid-1900s. It has since then evolved into a modern art form...

  • Paper and ink testing
    Paper and ink testing
    A variety of tests are used to determine ink and paper quality, and to measure their interactions. They are necessary to balance print quality, cost, and wear on the press.-List of paper and ink tests:Some of the paper and ink tests are listed here:...


  • Paper engineering
    Paper engineering
    For other uses, see Paper foldingPaper engineering is a branch of engineering that deals with the usage of physical science and life sciences in conjunction with mathematics as applied to the converting of renewable raw materials into useful and valuable products...

  • Paper recycling
    Paper recycling
    Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. Mill broke is paper trimmings and other paper...

  • Paper size
    Paper size
    Many paper size standards conventions have existed at different times and in different countries. Today there is one widespread international ISO standard and a localised standard used in North America . The paper sizes affect writing paper, stationery, cards, and some printed documents...

    , sizing
    Sizing
    Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

  • Paper chemicals
    Paper chemicals
    -Optical brightening agent:Optical brightener is used to make paper appear more white. Optical brightening agents use fluorescence to absorb invisible radiation from the ultraviolet part of the light spectrum and re-emit the radiation as light in the visible blue range. The optical brightening...

  • Paper towels
  • Papier-mâché
    Papier-mâché
    Papier-mâché , alternatively, paper-mache, is a composite material consisting of paper pieces or pulp, sometimes reinforced with textiles, bound with an adhesive, such as glue, starch, or wallpaper paste....


  • Papier
    Papier
    Papier may refer to :* paper in French, Dutch, Polish or German, word that can be found in the following expressions :** Papier-mâché, a construction material made of pieces of paper stuck together using a wet paste,...

     "paper" in French or German
  • Papyrus
    Papyrus
    Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt....

  • Roll hardness tester
    Roll hardness tester
    A roll hardness tester is a device to measure the roll hardness, hardness profile and hardness variation of paper rolls.-Method:In the preparation phase, the plunger, guide bar and guide disk are pushed forward by the compression spring. At the end of the movement the hammer mass is hooked by the...

  • Security paper
    Security paper
    Security paper is paper which incorporates features which can act to identify or authenticate a document as original or features which demonstrate tamper evidence when fraud is attempted, e.g., to remove or alter print such as amounts or signatures on a cheque...

  • Seed paper
    Seed paper
    Seed paper is a type of handmade paper that includes any number of different plant seeds. Seed paper is attractive, versatile, and easily recyclable. One of the novel features of seed paper is that it is a medium for viable plant seeds...

  • Toilet paper
    Toilet paper
    Toilet paper is a soft paper product used to maintain personal hygiene after human defecation or urination. However, it can also be used for other purposes such as blowing one's nose when one has a cold or absorbing common spills around the house, although paper towels are more used for the latter...

  • Wood Pulp
    Pulp (paper)
    Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...



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