Paper

Hand-made paper

Machine-made paper

Paper categories

Paper weights

Resources

Paper was probably first produced from bamboo and rag fibers about 2,000 years ago. By the eighth century, papermaking technology had spread to the Middle East. By the middle of the twelfth century, the Moors had transplanted the technology to Spain, from where it spread throughout Europe. Rags continued to be the chief source of paper fibers until the introduction of papermaking machinery in the early 1800s, when it became possible to obtain papermaking fibers from wood.

Hand-made and machine-made papers both consist of tiny cellulosic fibers pressed together in a thin sheet. Each of these fibers is a tiny tube, about 100 times as long as it is wide. Today, most fibers come from wood, though in earlier times, the source was more likely to have been rags of linen or cotton. The length of wood fibers from conifers is about 0.13-0.25 in (0.33-0.64 cm), and from hardwoods, about 0.04 in (0.10 cm). Other vegetable fibers are much longer. Cotton fibers, for example, may be one or more inches in length, with diameters of 0.02 in (0.05 cm). The source material is reduced to a slurry of fibers that floats freely in water, and many of the fibers will have been broken or cut when making the pulp. When the water is removed, the fibers form a thin layer of pulp which eventually becomes paper.

Hand-made paper

Rags to be made into paper are first sorted, and any unsuitable ones are discarded. Seams are opened, and nonfabric materials, such as buttons, are removed. The rags are chopped into small pieces and then cleaned by boiling them in strong cleansing solutions. Next, they are rinsed and beaten while damp until all of the threads have disintegrated and the fibers float freely in water. This is the paper pulp.

The very dilute pulp is next sent to the vat where the paper will actually be made. A rectangular mold containing wires running at right angles to each other is used to make a film of the pulp. Traditional molds have thin, closely spaced parallel wires running across the mold at the surface. These are attached to thick, widely spaced wires beneath them that run in the opposite direction. Paper formed on this type of mold typically reveals a ladder like pattern when held up to the light, and is known as laid paper. Woven paper is formed on a mold of plain, woven wire screening. Thin wire forming a design may be attached to the mold’s surface wires to produce a watermark in the finished paper. A rectangular frame, called the deckle, is placed over the mold to convert the mold into a sort of tray.

The papermaker then dips the mold with the deckle attached into the vat of dilute pulp and draws up a small amount of pulp on the surface of the wire. The mold is then shaken and tilted until most of the water has drained through the wire. The deckle is removed, and additional water is allowed to drain off. A second worker takes the mold and transfers the film of pulp to a piece of damp felt, laying a second piece of felt across the top.

This process continues until a stack of alternating wet paper and felt has built up. The stack is placed in a press to eliminate any residual water. Then the paper and felt are separated, and the paper is pressed by itself and hung up to dry. When dry, the paper sheets are dipped in a tub containing size (essentially gelatin or very dilute glue) and dried again. This gives the paper a harder and less absorbent finish than it would otherwise have had.

All paper was made by hand until the early nineteenth century. Artists use most of the handmade paper consumed today, though hand printers can still be found who believe it the finest printing surface available.

Machine-made paper

Hardly any paper for book printing is made from rags today. Wood now is the main ingredient of paper pulp, though the better papers contain cotton fiber, and the best are made entirely of cotton. The fibers are converted into pulp by chemical and/or mechanical means.

Chemical pulp starts with logs that have had their bark peeled off and that have been reduced to chips. The wood chips are boiled in strong caustic solutions that dissolve away parts of the wood that are not cellulose, such as lignin and resin, and leave the cellulose fibers more or less free. There are two chief processes for producing chemical pulp: the kraft process, and the sulfite process. The kraft process uses the wood of either deciduous (e.g., poplar) or coniferous trees (e.g., spruce, fir, and hemlock) and produces a very strong paper. The sulfite process is less widely used and employs only coniferous wood and an acid solution in paper manufacture.

Mechanical pulp is mostly made by stone-grinding peeled logs in a stream of water so that the wood is broken up into fibers. Spruce, balsam, and hemlock are the woods considered best suited for pulping by this process. The ground wood contains all of the constituents of the original wood, including those that would have been eliminated as impurities in chemical pulp manufacturing. Mechanical pulp is mainly used for newsprint because paper made from mechanical pulp quickly discolors and becomes brittle. It also tends to be weak. A superior, stronger form of mechanical pulp is called thermomechanical pulp. It is made from wood chips treated by steam under high pressure. Mechanical pulp is sometimes added to chemical pulp for making low cost book papers. A paper containing no mechanical pulp is called a free sheet.

Before the pulp can be made into paper, it is necessary to mechanically beat or refine it. It is also usually bleached with chlorine and calcium hypochlorite. Unbleached kraft pulp is used for grocery bags and heavy wrapping paper. Other materials may also be added to the pulp depending on the type of paper to be made. For book paper, fillers such as white clay and titanium oxide may be added to provide opaqueness and extra whiteness. Size may be added for stiffness and smoothness. Dyes are added for tinted papers. The specific combination of pulp and additives used to produce a particular type of paper is called the furnish for that paper. With better grades of paper, care is taken to produce a furnish that is chemically neutral (pH 7 on the acid-base scale). For a paper to have long life, it must be acid-free.

The machine that converts the pulp into paper is called a fourdrinier machine, after Henry and Sealy Fourdrinier who financed its development in England in the early 1800s. The fourdrinier machine takes pulp that is still 99% water and converts it into a continuous web of paper containing only a small amount of moisture.

Pulp is continuously fed into the fourdrinier machine on the surface of a moving endless belt of fine mesh screening, usually made of nylon. Deckle straps prevent the liquid pulp from slopping over the sides. The screening is shaken from side to side as it moves forward to help drain the water. Suction boxes below the screening pull more water through, as a wire-mesh-covered cylinder presses on the web of pulp from above. The cylinder may be covered with a plain wire cloth to impart a wove effect, or with wire in a ladder pattern to produce a laid effect. To produce a watermark, the papermaker attaches a wire design to the cylinder.

The now very soggy paper is placed on an endless belt of wool felt that carries it between a series of rollers that squeeze more water from it. It then passes over a series of very large, steam-heated, cast-iron drums that complete the drying process. During drying, the web is held tightly against the hot drums by endless belts of fabric.

After the paper has dried, it is usually run through a series of highly polished metal (calendar) rollers that further compact it and smooth its surface. The calendar rolls are arranged in pairs; each pair rolls at a different speed; this effectively polishes the paper. A variety of calendared finishes can be obtained, ranging from antique (softest and dullest), through eggshell, vellum, machine finish, to English finish (hardest and shiniest available without further treatment).

Further treatment may include supercalendaring, surface sizing, or coating. Supercalendaring is a polishing process similar to the calendaring process but done on a separate machine. The final finish of coated papers are brushed or rolled on in liquid form. The finish may be matte or glossy. Most papers include size in the furnish, but additional sizing may be added to the surface by running the paper through a vat of sizing material to provide a harder finish after the paper is made. The paper may be coated with fine clay. The clay is adhered to the surface of the paper with adhesives. The paper is then supercalendared with extremely smooth rollers. Dull coated papers are made with clays that finish dull, and are less calendared. Other papers are gloss coated. Papers may be coated on one or both sides.

Machine-made paper has a pronounced grain, as evidenced by its tendency to tear and fold preferentially in one direction. This is because the cellulose fibers tend to align themselves in the direction of travel as the pulp is laid down on the wire. Shaking does not completely achieve random alignment. In reeled paper, the grain always runs lengthwise. In sheet paper, the grain may run either the long way or the short way, depending on how it was cut from the reel.

Like most fabrics, paper has a right and wrong side. The bottom of the web (called the wire side) next to the screening at the wet end of the fourdrinier machine is slightly rougher than the top (or felt) side. If only one side of the paper is to be used, the smoother side is usually chosen. Paper made on a twin-wire fourdrinier machine has either two felt sides or two wire sides; this is because two webs of pulp are laid down simultaneously and pressed together as the paper is dried and finished. One-sided paper is more expensive than ordinary two-sided paper.

Paper categories

Paper is available in a wide variety of weights, colors, textures, and finishes for a multitude of purposes. Book papers are intended for book and journal printing. Almost all bookpapers are surface-sized for offset lithography. The sizing resists penetration by the water and ink used in offset printing. Book papers are mainly made from Kraft pulp, sometimes with machine pulp added. Text papers are available in many colors and textures for use in advertising leaflets, endpapers, etc. They are also sized for offset printing. Cover papers are used for heavier papers, and are chiefly used for covers for pamphlets, journals, and paperback books. Newsprint is made for printing newspapers, advertising catalogs, inexpensive paperbacks, and other items that will probably only be read once if at all, and then thrown away. It is made from machine pulp, usually with some chemical pulp added for strength. Bond is made mainly for office use and ranges in quality from top-grade papers made from 100% rag pulp to low-grade stocks consisting largely of machine pulp.

Paper weights

Paper varies in thickness and weight. Both measurements are used to calibrate stock. At the paper mill, the thickness of a sheet is measured in thousands of an inch (mils). For the purposes of bookmaking, this number is converted into pages per inch. Book papers may vary from 200 to nearly 1,000 pages per inch, but the commonly used 50-lb (23 kg) machine-finished papers generally run about 500-550 pages per inch, each leaf counting as two pages. That corresponds to an average thickness of about 0.004 in (4 mils) for the thickness of one sheet of 50-lb (23 kg) machine-finished paper.

Paper is sold by weight. Different grades of the same type of paper are distinguished by the weight of some standard quantity of that paper. For most of the world, the standard quantity is one sheet of paper per one square meter in area. In the United States, the system of basis weights is used to compare the weights of papers. The standard quantity is one ream, or 500 sheets, but the standard sheet size varies from one category of paper to another. For book papers, the standard sheet measures 25× 38 in (64× 97 cm). For cover stocks, the standard size is only 20× 26 in (51× 66 cm), so a 50-lb (23 kg) cover paper is nearly twice as heavy as a 50-lb (23 kg) book paper. For bond papers, the standard size is 17× 22 in (43× 56 cm), so a 20-lb

KEY TERMS

Calendar rolls —Highly polished metal rollers used to compact paper after it has dried.

Fourdrinier machine —The machine that forms paper from pulp, named after the English family that financed its development in the early 1800s.

Furnish —Specific combination of pulp and other ingredients used to make a particular kind of paper.

Kraft process —A process in which sodium sulfate is reduced by heating with carbonaceous matter in a furnace to form sodium sulfide, which is then used in a water solution with sodium hydroxide as a cooking liquor. The wood pulp is then cooked under pressure and at high temperatures. The kraft process, also known as the sulfate process, has a less corrosive influence on iron and steel than the sulfite process.

Sulfite process —A process in which sulfur dioxide is passed through calcium carbonate to form calcium bisulfite in an excess of sulphurous acid as the cooking liquor. The wood pulp is then cooked under pressure at high temperatures.

(9 kg) bond is approximately equal to a 50-lb (23 kg) book paper.

In Europe, the metric A series of stock sizes is based on a standard sheet of paper, rectangular in shape (841 mm× 1189 mm) and one meter in area. This is called size A0. Cutting this sheet in half produces size A1; cutting the A1 sheet in half produces size A2, and so on down to size A5, which is 1/32 the area of A0. In this sizing system, all of the sheets have the same shape: the ratio of the short side to the long side is identical throughout the series of sizes.

Resources

Books

Asuncion, Josep. The Complete Book of Papermaking. New York: Lark Books, 2003.

Hunter, Dard. Papermaking: The History and Technique of an Ancient Craft. New York: Dover Publications, Inc., 1974.

Lee, Marshall. Bookmaking. New York: R. R. Bowker Company, 1979.

Shannon, Faith. The Art and Craft of Paper. San Francisco: Chronicle Books, 1994.

Randall Frost

Paper

Paper was probably first produced from bamboo and rag fibers about 2,000 years ago. By the eighth century, papermaking technology had spread to the Middle East. By the middle of the twelfth century, the Moors had transplanted the technology to Spain, from where it spread throughout Europe . Rags continued to be the chief source of paper fibers until the introduction of papermaking machinery in the early 1800s, when it became possible to obtain papermaking fibers from wood .

Hand-made and machine-made papers both consist of tiny cellulosic fibers pressed together in a thin sheet. Each of these fibers is a tiny tube, about 100 times as long as it is wide. Today, most fibers come from wood, though in earlier times, the source was more likely to have been rags of linen or cotton . The length of wood fibers from conifers is about 0.13-0.25 in (0.33-0.64 cm), and from hardwoods, about 0.04 in (0.10 cm). Other vegetable fibers are much longer. Cotton fibers, for example, may be one or more inches in length, with diameters of 0.02 in (0.05 cm). The source material is reduced to a slurry of fibers that floats freely in water , and many of the fibers will have been broken or cut when making the pulp. When the water is removed, the fibers form a thin layer of pulp which eventually becomes paper.

Hand-made paper

Rags to be made into paper are first sorted, and any unsuitable ones are discarded. Seams are opened, and nonfabric materials, such as buttons, are removed. The rags are chopped into small pieces and then cleaned by boiling them in strong cleansing solutions. Next, they are rinsed and beaten while damp until all of the threads have disintegrated and the fibers float freely in water. This is the paper pulp.

The very dilute pulp is next sent to the vat where the paper will actually be made. A rectangular mold containing wires running at right angles to each other is used to make a film of the pulp. Traditional molds have thin, closely spaced parallel wires running across the mold at the surface. These are attached to thick, widely spaced wires beneath them that run in the opposite direction. Paper formed on this type of mold typically reveals a ladder-like pattern when held up to the light , and is known as laid paper. Woven paper is formed on a mold of plain, woven wire screening. Thin wire forming a design may be attached to the mold's surface wires to produce a watermark in the finished paper. A rectangular frame, called the deckle, is placed over the mold to convert the mold into a sort of tray.

The papermaker then dips the mold with the deckle attached into the vat of dilute pulp and draws up a small amount of pulp on the surface of the wire. The mold is then shaken and tilted until most of the water has drained through the wire. The deckle is removed, and additional water is allowed to drain off. A second worker takes the mold and transfers the film of pulp to a piece of damp felt, laying a second piece of felt across the top.

This process continues until a stack of alternating wet paper and felt has built up. The stack is placed in a press to eliminate any residual water. Then the paper and felt are separated, and the paper is pressed by itself and hung up to dry. When dry, the paper sheets are dipped in a tub containing size (essentially gelatin or very dilute glue) and dried again. This gives the paper a harder and less absorbent finish than it would otherwise have had.

All paper was made by hand until the early nineteenth century. Artists use most of the handmade paper consumed today, though hand printers can still be found who believe it the finest printing surface available.

Machine-made paper

Hardly any paper for book printing is made from rags today. Wood now is the main ingredient of paper pulp, though the better papers contain cotton fiber, and the best are made entirely of cotton. The fibers are converted into pulp by chemical and/or mechanical means.

Chemical pulp starts with logs that have had their bark peeled off and that have been reduced to chips. The wood chips are boiled in strong caustic solutions that dissolve away parts of the wood that are not cellulose , such as lignin and resin, and leave the cellulose fibers more or less free. There are two chief processes for producing chemical pulp: the kraft process, and the sulfite process. The kraft process uses the wood of either deciduous (e.g., poplar) or coniferous trees (e.g., spruce , fir, and hemlock) and produces a very strong paper. The sulfite process is less widely used and employs only coniferous wood and an acid solution in paper manufacture.

Mechanical pulp is mostly made by stone-grinding peeled logs in a stream of water so that the wood is broken up into fibers. Spruce, balsam, and hemlock are the woods considered best suited for pulping by this process. The ground wood contains all of the constituents of the original wood, including those that would have been eliminated as impurities in chemical pulp manufacturing. Mechanical pulp is mainly used for newsprint because paper made from mechanical pulp quickly discolors and becomes brittle. It also tends to be weak. A superior, stronger form of mechanical pulp is called thermomechanical pulp. It is made from wood chips treated by steam under high pressure . Mechanical pulp is sometimes added to chemical pulp for making low cost book papers. A paper containing no mechanical pulp is called a free sheet.

Before the pulp can be made into paper, it is necessary to mechanically beat or refine it. It is also usually bleached with chlorine and calcium hypochlorite. Unbleached kraft pulp is used for grocery bags and heavy wrapping paper. Other materials may also be added to the pulp depending on the type of paper to be made. For book paper, fillers such as white clay and titanium oxide may be added to provide opaqueness and extra whiteness. Size may be added for stiffness and smoothness. Dyes are added for tinted papers. The specific combination of pulp and additives used to produce a particular type of paper is called the furnish for that paper. With better grades of paper, care is taken to produce a furnish that is chemically neutral (pH 7 on the acid-base scale). For a paper to have long life, it must be acid-free.

The machine that converts the pulp into paper is called a fourdrinier machine, after Henry and Sealy Fourdrinier who financed its development in England in the early 1800s. The fourdrinier machine takes pulp that is still 99% water and converts it into a continuous web of paper containing only a small amount of moisture.

Pulp is continuously fed into the fourdrinier machine on the surface of a moving endless belt of fine mesh screening, usually made of nylon. Deckle straps prevent the liquid pulp from slopping over the sides. The screening is shaken from side to side as it moves forward to help drain the water. Suction boxes below the screening pull more water through, as a wire-mesh-covered cylinder presses on the web of pulp from above. The cylinder may be covered with a plain wire cloth to impart a wove effect, or with wire in a ladder pattern to produce a laid effect. To produce a watermark, the paper-maker attaches a wire design to the cylinder.

The now very soggy paper is placed on an endless belt of wool felt that carries it between a series of rollers that squeeze more water from it. It then passes over a series of very large, steam-heated, cast-iron drums that complete the drying process. During drying, the web is held tightly against the hot drums by endless belts of fabric.

After the paper has dried, it is usually run through a series of highly polished metal (calendar) rollers that further compact it and smooth its surface. The calendar rolls are arranged in pairs; each pair rolls at a different speed; this effectively polishes the paper. A variety of calendared finishes can be obtained, ranging from antique (softest and dullest), through eggshell, vellum, machine finish, to English finish (hardest and shiniest available without further treatment).

Further treatment may include supercalendaring, surface sizing, or coating. Supercalendaring is a polishing process similar to the calendaring process but done on a separate machine. The final finish of coated papers are brushed or rolled on in liquid form. The finish may be matte or glossy. Most papers include size in the furnish, but additional sizing may be added to the surface by running the paper through a vat of sizing material to provide a harder finish after the paper is made. The paper may be coated with fine clay. The clay is adhered to the surface of the paper with adhesives. The paper is then supercalendared with extremely smooth rollers. Dull coated papers are made with clays that finish dull, and are less calendared. Other papers are gloss coated. Papers may be coated on one or both sides.

Machine-made paper has a pronounced grain, as evidenced by its tendency to tear and fold preferentially in one direction. This is because the cellulose fibers tend to align themselves in the direction of travel as the pulp is laid down on the wire. Shaking does not completely achieve random alignment. In reeled paper, the grain always runs lengthwise. In sheet paper, the grain may run either the long way or the short way, depending on how it was cut from the reel.

Like most fabrics, paper has a right and wrong side. The bottom of the web (called the wire side) next to the screening at the wet end of the fourdrinier machine is slightly rougher than the top (or felt) side. If only one side of the paper is to be used, the smoother side is usually chosen. Paper made on a twin-wire fourdrinier machine has either two felt sides or two wire sides; this is because two webs of pulp are laid down simultaneously and pressed together as the paper is dried and finished. One-sided paper is more expensive than ordinary two-sided paper.

Paper categories

Paper is available in a wide variety of weights, colors, textures, and finishes for a multitude of purposes. Book papers are intended for book and journal printing. Almost all bookpapers are surface-sized for offset lithography . The sizing resists penetration by the water and ink used in offset printing. Book papers are mainly made from Kraft pulp, sometimes with machine pulp added. Text papers are available in many colors and textures for use in advertising leaflets, endpapers, etc. They are also sized for offset printing. Cover papers are used for heavier papers, and are chiefly used for covers for pamphlets, journals, and paperback books. Newsprint is made for printing newspapers, advertising catalogs, inexpensive paperbacks, and other items that will probably only be read once if at all, and then thrown away. It is made from machine pulp, usually with some chemical pulp added for strength. Bond is made mainly for office use and ranges in quality from top-grade papers made from 100% rag pulp to low-grade stocks consisting largely of machine pulp.

Paper weights

Paper varies in thickness and weight. Both measurements are used to calibrate stock. At the paper mill, the thickness of a sheet is measured in thousands of an inch (mils). For the purposes of bookmaking, this number is converted into pages per inch. Book papers may vary from 200 to nearly 1,000 pages per inch, but the commonly used 50-lb (23-kg) machine-finished papers generally run about 500-550 pages per inch, each leaf counting as two pages. That corresponds to an average thickness of about 0.004 in (4 mm) for the thickness of one sheet of 50 lb (23 kg) machine-finished paper.

Paper is sold by weight. Different grades of the same type of paper are distinguished by the weight of some standard quantity of that paper. For most of the world, the standard quantity is one sheet of paper per one square meter in area. In the United States, the system of basis weights is used to compare the weights of papers. The standard quantity is one ream, or 500 sheets, but the standard sheet size varies from one category of paper to another. For book papers, the standard sheet measures 25 x 38 in (64 x 97 cm). For cover stocks, the standard size is only 20 x 26 in (51 x 66 cm), so a 50 lb (23 kg) cover paper is nearly twice as heavy as a 50 lb (23 kg) book paper. For bond papers, the standard size is 17 x 22 in (43 x 56 cm), so a 20 lb (9 kg) bond is approximately equal to a 50 lb (23 kg) book paper.

In Europe, the metric A series of stock sizes is based on a standard sheet of paper, rectangular in shape (841 mm x 1189 mm) and one meter in area. This is called size A0. Cutting this sheet in half produces size A1; cutting the A1 sheet in half produces size A2, and so on down to size A5, which is 1/32 the area of A0. In this sizing system, all of the sheets have the same shape: the ratio of the short side to the long side is identical throughout the series of sizes.

Resources

books

The Chicago Manual of Style. Chicago: The University of Chicago Press, 1982.

Hunter, Dard. Papermaking: The History and Technique of an Ancient Craft. New York: Dover Publications, Inc., 1974.

Lee, Marshall. Bookmaking. New York: R. R. Bowker Company, 1979.

Shannon, Faith. The Art and Craft of Paper. San Francisco: Chronicle Books, 1994.

Randall Frost

KEY TERMS

Calendar rolls

—Highly polished metal rollers used to compact paper after it has dried.

Fourdrinier machine

—The machine that forms paper from pulp, named after the English family that financed its development in the early 1800s.

Furnish

—Specific combination of pulp and other ingredients used to make a particular kind of paper.

Kraft process

—A process in which sodium sulfate is reduced by heating with carbonaceous matter in a furnace to form sodium sulfide, which is then used in a water solution with sodium hydroxide as a cooking liquor. The wood pulp is then cooked under pressure and at high temperatures. The kraft process, also known as the sulfate process, has a less corrosive influence on iron and steel than the sulfite process.

Sulfite process

—A process in which sulfur dioxide is passed through calcium carbonate to form calcium bisulfite in an excess of sulphurous acid as the cooking liquor. The wood pulp is then cooked under pressure at high temperatures.

Paper

Background

Formed from wood pulp or plant fiber, paper is chiefly used for written communication. The earliest paper was papyrus, made from reeds by the ancient Egyptians. Paper was made by the Chinese in the second century, probably by a Chinese court official named Cai Lun. His paper was made from such things as tree bark and old fish netting. Recognized almost immediately as a valuable secret, it was 500 years before the Japanese acquired knowledge of the method. Papermaking was known in the Islamic world from the end of the eighth century a.d.

Knowledge of papermaking eventually moved westward, and the first European paper mill was built at Jativa, in the province of Valencia, Spain, in about 1150. By the end of the 15th century, paper mills existed in Italy, France, Germany, and England, and by the end of the 16th century, paper was being made throughout Europe.

Paper, whether produced in the modern factory or by the most careful, delicate hand methods, is made up of connected fibers. The fibers can come from a number of sources including cloth rags, cellulose fibers from plants, and, most notably, trees. The use of cloth in the process has always produced high-quality paper. Today, a large proportion of cotton and linen fibers in the mix create many excellent papers for special uses, from wedding invitation paper stock to special paper for pen and ink drawings.

The method of making paper is essentially a simple one—mix up vegetable fibers, and cook them in hot water until the fibers are soft but not dissolved. The hot water also contains a base chemical such as lye, which softens the fibers as they are cooking. Then, pass a screen-like material through the mixture, let the water drip off and/or evaporate, and then squeeze or blot out additional water. A layer of paper is left behind. Essential to the process are the fibers, which are never totally destroyed, and, when mixed and softened, form an interlaced pattern within the paper itself. Modern papermaking methods, although significantly more complicated than the older ways, are developmental improvements rather than entirely new methods of making paper.

Raw Materials

Probably half of the fiber used for paper today comes from wood that has been purposely harvested. The remaining material comes from wood fiber from sawmills, recycled newspaper, some vegetable matter, and recycled cloth. Coniferous trees, such as spruce and fir, used to be preferred for papermaking because the cellulose fibers in the pulp of these species are longer, therefore making for stronger paper. These trees are called "softwood" by the paper industry. Deciduous trees (leafy trees such as poplar and elm) are called "hardwood." Because of increasing demand for paper, and improvements in pulp processing technology, almost any species of tree can now be harvested for paper.

Some plants other than trees are suitable for paper-making. In areas without significant forests, bamboo has been used for paper pulp, as has straw and sugarcane. Flax, hemp, and jute fibers are commonly used for textiles and rope making, but they can also be used for paper. Some high-grade cigarette paper is made from flax.

Cotton and linen rags are used in fine-grade papers such as letterhead and resume paper, and for bank notes and security certificates. The rags are usually cuttings and waste from textile and garment mills. The rags must be cut and cleaned, boiled, and beaten before they can be used by the paper mill.

Other materials used in paper manufacture include bleaches and dyes, fillers such as chalk, clay, or titanium oxide, and sizings such as rosin, gum, and starch.

The Manufacturing
Process

Making pulp

• 1 Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution ofsodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.

Beating

• 2 The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.

Pulp to paper

• 3 In order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.

  The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.

Finishing

• 4 Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.

  The paper may be further finished by passing through a vat of sizing material. It may also receive a coating, which is either brushed on or rolled on. Coating adds chemicals or pigments to the paper's surface, supplementing the sizings and fillers from earlier in the process. Fine clay is often used as a coating. The paper may next be supercalendered, that is, run through extremely smooth calendar rollers, for a final time. Then the paper is cut to the desired size.

Environmental Concerns

The number of trees and other vegetation cut down in order to make paper is enormous. Paper companies insist that they plant as many new trees as they cut down. Environmentalists contend that the new growth trees, so much younger and smaller than what was removed, cannot replace the value of older trees. Efforts to recycle used paper (especially newspapers) have been effective in at least partially mitigating the need for destruction of woodlands, and recycled paper is now an important ingredient in many types of paper production.

The chemicals used in paper manufacture, including dyes, inks, bleach, and sizing, can also be harmful to the environment when they are released into water supplies and nearby land after use. The industry has, sometimes with government prompting, cleared up a large amount of pollution, and federal requirements now demand pollutionfree paper production. The cost of such clean-up efforts is passed on to the consumer.

Where To Learn More

Books

Biermann, Christopher J. Essentials of Pulping & Papermaking. Academic Press, 1993.

Bell, Lilian A. Plant Fibers for Papermaking. Liliaceae Press, 1992.

Ferguson, Kelly, ed. New Trends and Developments in Papermaking. Miller Freeman, Inc., 1994.

Munsell, Joel. Chronology and Process of Papermaking, 1876-1990. Albert Saifer Publisher, 1992.

Periodicals

deGrassi, Jennifer. "Primitive Papermaking." Schools Arts, February 1981, pp. 32-33.

Kleiner, Art. "Making Paper." Co-Evolution Quarterly, Winter 1980, p. 138.

Lamb, Lynette. "Tree-Free Paper." Utne Reader, March-April 1994, p. 40.

Saddington, Marrianne. "How to Make Homemade Paper." Mother Earth News, December-January 1993, p. 30+.

Sessions, Larry. "Making Paper." Family Explorer, October 1994.

—Lawrence H. Berlow

Paper

Paper is an indispensable part of everyday life. Beyond its use as the basic material for written and printed communication, paper in its various forms are used for hundreds of other purposes, including packaging, wrapping, insulating, and toweling. Each year, Americans use an average of 750 pounds (340 kilograms) of paper products per person. That equates to 210 billion pounds (95 billion kilograms) of paper products used in the United States per year.

The word paper comes from papyrus, a reedy plant that used to grow abundantly along the Nile River in Egypt. Centuries ago, ancient Egyptians removed the fibrous layers from the stem of this plant and cemented them together to create a durable woven writing material also known as papyrus. Examples of papyrus manuscripts have survived to the present.

Many sources claim that paper (as we know it) was first invented in a.d. 105 by Ts'ai Lun, a Chinese court official. Historians believe he mixed mulberry bark, hemp, and rags with water, mashed it into a pulp, pressed out the liquid, then hung the thin mat on a mold of bamboo strips to dry in the Sun. Paper made from rags in about a.d. 150 still exists today.

By the early seventh century, paper and its production had been introduced into Japan. From here, it spread to Central Asia by 750. Paper did not make its way into Europe until about 1150, but it spread throughout the continent over the next few centuries. Rags were the chief source of paper fibers until the introduction of papermaking machinery in the early nineteenth century, when it became possible to obtain papermaking fibers from wood.

Words to Know

Calendar rolls: Highly polished metal rollers used to compact and smooth paper after it has dried.

Cellulose: An insoluble carbohydrate that plants use as building material to make their cell walls.

Deckle: Frame around the edges of a mold used to make paper by hand; also, either of the straps around the edge of the screening of a papermaking machine.

Fourdrinier machine: Machine that forms paper from pulp, named after the English brothers who financed its development in the early nineteenth century.

Today, paper can be both handmade and machine-made. Both types of paper consist of tiny cellulose fibers pressed together in a thin sheet. Each of these fibers is a tiny tube, about 100 times as long as it is wide. Today, most fibers come from wood, though in earlier times, the source was more likely to have been rags of linen or cotton. The source material is reduced to a slurry of fibers that float freely in water, and many of the fibers will have been broken or cut when making the pulp. When the water is removed, the fibers form a thin layer of pulp that eventually becomes paper.

Handmade paper

Rags to be made into paper are first sorted, and any unsuitable ones are discarded. Seams are opened and items such as buttons are removed. The rags are chopped into small pieces, which are then boiled in strong cleansing solutions. Next, the pieces are rinsed and beaten while damp until all of the threads have disintegrated and the fibers float freely in water. This is the paper pulp.

The very dilute pulp is next sent to the vat where the paper will actually be made. A rectangular mold containing wires running at right angles to each other is used to make a film of the pulp. Traditional molds have thin, closely spaced parallel wires running across the mold at the surface. These are attached to thick, widely spaced wires beneath them that run perpendicular or in the opposite direction. Paper formed on this type of mold typically reveals a ladder-like pattern when held up to the light, and is known as laid paper. Woven paper is formed on a mold of plain, woven wire screening. Thin wire forming a design may be attached to the mold's surface wires to produce a watermark in the finished paper. A rectangular frame, called the deckle, is placed over the mold to convert the mold into a sort of tray.

The papermaker then dips the mold with the deckle attached into the vat of dilute pulp and draws up a small amount of pulp on the surface of the wire. The mold is then shaken and tilted until most of the water has drained through the wire. The deckle is removed, and additional water is allowed to drain off. A second worker takes the mold and transfers the film of pulp to a piece of damp felt, laying a second piece of felt across the top.

This process continues until a stack of alternating wet paper and felt has built up. The stack is placed in a press to eliminate any residual

water. Then the paper and felt are separated, and the paper is pressed by itself and hung up to dry. When dry, the paper sheets are dipped in a tub containing gelatin or very dilute glue and dried again. This gives the paper a harder and less absorbent finish than it would otherwise have had.

All paper was made by hand until the early nineteenth century. Artists use most of the handmade paper produced today, although many other people believe it to be the finest printing surface available.

Machine-made paper

Hardly any paper for book printing is made from rags today. Wood is the main ingredient of paper pulp, though the better papers contain cotton fiber, and the best are made entirely of cotton. The fibers are converted into pulp by chemical or mechanical means. Chemical pulp is used to make fine white paper, whereas mechanical pulp is used to make newsprint, tissue, towel, and other inexpensive papers.

Chemical pulp begins with the debarking of logs. Chippers with whirling blades reduce the logs to smaller and smaller chips. The wood chips are then boiled in a large vat called a digester that contains strong caustic solutions that dissolve away parts of the wood that are not cellulose. This leaves only pure fibers of cellulose.

Mechanical pulp also begins with debarked logs. The logs are then ground up into fibers by a rapidly revolving grindstone. Spruce, balsam, and hemlock are the woods considered best suited for pulping by this process. Unlike chemical pulp, mechanical pulp contains all of the parts of the original wood. Because of this, mechanical pulp is weak and tends to discolor quickly. If mechanical pulp is to be used to make white paper, it is usually bleached with chlorine dioxide or sodium hydroxide. Paper pulp used to be bleached with chlorine, but the U.S. Environmental Protection Agency (EPA) determined that the process of bleaching paper with chlorine produces dioxin, a carcinogen or cancer-causing agent. In 1998, the EPA mandated that paper companies switch to safer compounds

The machine that converts either type of pulp into paper is called a fourdrinier machine, after English brothers Henry and Sealy Fourdrinier, who financed its development in 1803. The fourdrinier machine takes pulp that is almost 100 percent water and, by removing almost all the water, changes it into a continuous web of paper.

Watery pulp enters the fourdrinier machine on an endless moving belt of nylon mesh screening. As it moves forward, the screening is agitated from side to side to drain the excess water. Deckle straps prevent the liquid pulp from slopping over the sides. Air suction pumps beneath the screening also pull more water through. As the pulp passes along on the belt, a turning cylinder presses on it from above. This cylinder, called a dandy roll, is covered with wire mesh that imparts either a wove or a laid surface to pulp, depending on the pattern of the mesh.

At the end of the fourdrinier machine is a series of felt-covered rollers. As the pulp (now very wet paper) passes through them, they press still more water out of it, condensing the fibers. The paper then passes through sets of smooth metal press rollers that give a smooth finish to both surfaces of the paper. The drying process is completed after the fully formed paper passes through a series of large heated rollers. Once dried, the paper undergoes calendaring, in which it is pressed between a series of smooth metal (calendar) rollers that give it a polished surface. Afterward, the paper is cut into sheets or wrapped into a roll.

pa·per / ˈpāpər/ • n. 1. material manufactured in thin sheets from the pulp of wood or other fibrous substances, used for writing, drawing, or printing on, or as wrapping material: a sheet of paper | [as adj.] a paper bag. ∎  a newspaper. ∎  wallpaper. ∎  (usu. papers) a piece or sheet of paper with something written or drawn on it: he riffled through the papers on his desk. ∎  (papers) significant or important documents belonging to a person: the personal papers of major political figures. ∎  [as adj.] denoting something that is officially documented but has no real existence or little merit or use: a paper profit. ∎  a government report or policy document: a recently leaked cabinet paper. ∎  (papers) documents attesting identity; credentials: two men stopped us and asked us for our papers. ∎  a piece of paper used for wrapping or enclosing something or made into a packet: toffee papers. ∎ short for commercial paper. ∎ short for cigarette paper.2. an essay or thesis, esp. one read at an academic lecture or seminar or published in an academic journal.3. theatrical slang free passes of admission to a theater or other entertainment.• v. [tr.] 1. (often be papered) apply wallpaper to (a wall or room): the walls were papered in a Regency stripe. ∎  [intr.] (paper over) cover (a hole or blemish) with wallpaper. ∎  (paper over) disguise (an awkward problem) instead of resolving it: the ill feeling between her and Jenny must have been papered over.2. theatrical slang fill (a theater) by giving out free tickets.PHRASES: be not worth the paper it is written on be of no value or validity whatsoever despite having been written down.make the papers be written about in newspapers and thus become famous or notorious.on paper in writing. ∎  in theory rather than in reality: the combatants were, on paper at least, evenly matched.DERIVATIVES: pa·per·er n.pa·per·less adj.