Historical Background and General Aspects
Paper is defined internationally as a thin layer of mostly cellulosic plant fibers, produced on a screen by dewatering a slurry of fibers in water

[2]. The slurry is called pulp. Despite recent developments (proteinic or synthetic fibers, chemical additives, coating, etc.) the “cellulosic plant fiber” will be the main, not exclusive, component of paper, and water will be used in preparing the pulp and in forming the paper web also in the future.

Precursors of Paper Tapa (Bark-cloth)
Bark-cloth, made since prehistoric times, is found widely along the Equator belt in nearly all cultures, used mainly for decorating and clothing [3]. It is produced by beating or pressing the inner bark (liber, bast) of trees and shrubs like paper mul¬berry, lime-tree, fig or daphne, and is known by the generic term “tapa”, derived from the Polynesian language. Tapa is a felt-like material, similar to thick woven paper, showing in most cases traces of the beating mallets.

Technically speaking, it is a kind of non-woven paper.
There are three different techniques to be observed in tapa-making. The most sophisticated method consists of three steps. In the first, small strips of bast are cut and cooked for several hours in suds of wood ash. This cooking is very similar to the basic operation of our alkaline pulping. Then the strips are rinsed, placed together on a wooden board and beaten with a mallet, thus forming a small sheet on the board. The third step consists of drying and smoothing. Felt
Felting techniques go back into prehistory [4]. Plant fibers or animal hair are sepa¬rated from their original linking as much as possible and spread in thick layers onto a cloth or mat. Then they are covered by another cloth and beaten by foot stamping or with heavy wooden sticks to entangle them and stick them together. In another way, the ground mat bearing the fibers is rolled and the roll is beaten. The mat is unrolled and rolled again several times. In wet felting, water is used to soak the fibers and help felting. Papyrus
Papyrus, the most commonly used writing material of Ancient Egypt and Classical Antiquity, was made in Egypt from the beginning of the 3rd millennium BC. The triangulated stem of the papyrus plant is peeled and the pith cut into thin, small strips. A first layer of wet strips placed vertically side by side with a slight overlap is laid onto a board. Then, a similar layer of horizontally oriented stripes is laid above it. Beating with wooden sticks and pressing the still wet layers leads to a sheet of entangled fibers, most remaining in the original linking of the pith. After drying and smoothing several sheets are glued together to form a roll, ready to be written on. Gluing of several papyrus sheet fragments, usually recycled material, results in board or papier-mâché.

New papyrus rolls are very strong and flexible, an ideal writing material. They were exported in large quantities into the Mediterranean area until the 8th century AD. Parchment replaced the dwindling supply from Egypt. When paper was im¬ported from the East, it was given the name of the Egyptian writing material because of its resemblance to papyrus.

Paper Invention of Paper
The oldest papermaking technique, pouring pulp into a primitive mould, is still in use at a few locations in the Himalayas, in some remote spots of China and in Southeast Asia. It shows clearly the descent from tapa and felting techniques. From recent findings of the oldest papers in Chinese tombs or in refuse heaps of military posts it must be concluded that some kind of paper was produced in China since the final centuries BC. Nevertheless, the Chinese chronicles state that in 105 AD in Loyang, the court official Cai Lun invented papermaking from textile waste, i. e. from rags, and propagated paper as a writing material [5]. This was the birth of paper as we know it today. Chinese Paper
Chinese papermakers improved the effectiveness of the production, replacing the pouring technique by dipping the bamboo screen into a vat filled with diluted pulp. After lifting the mold out of the vat and dewatering, the newly formed sheet of paper was immediately couched on a wooden board or a plastered wall to let it dry. The flexible bamboo screen was rolled off and could be reused with the vat. Thus, the handicap of waiting until a sheet dried on the mold, was surmounted. Because of rag and paper mulberry shortages, they chose bamboo as a further source of fiber [6] the pulping of which took several months.
China developed many kinds of specialty papers (sized, coated and dyed paper; anti-moth paper; waterproof paper); over-size sheets were made by couching the wet borders of smaller sheets together, and decoration watermarks were added by putting leather or board figures on the screen before pouring the pulp. Paper served for almost everything: writing, drawing, wrapping, clothing, protection from wind and rain, decoration, windows, even for making balloons and kites, and, last but not least, for making paper money or special currency to be burned in honor of the ancestors. The Eastern Spread of Papermaking
Chinese papermaking techniques were introduced into Korea at an early date, and reached Japan in 610 AD. In both countries, fibers of the paper mulberry were mainly used. In Japan, splash dipping was developed, using a big mold suspended on a teetering twig [7]. Japanese papermakers were fond of art papers for decora¬tion purposes. The ultimate in Japanese papermaking was the production of Shifu, paper yarn woven into heavy, beautiful fabric.
1.3 Historical Background and General Aspects The Spread of Papermaking into Central and Southern Asia
At an early date (4th to 6th centuries AD), it is attested that there were Chinese papermakers in Central Asia along the Silk Road, using the very old technique and local fiber plants like black mulberry. There, Tibetans learned the papermaking craft and transferred the knowledge into the high valleys of the Himalayas where they used local plants like the roots of Stellera Chamaejasme. From Southern China, the old-fashioned pouring technique spread into the emerging kingdoms of South Eastern Asia. India kept its traditional use of bark, textile cloth and palm leaves as writing materials for a long time. Only at a later period (11th century AD?), was papermaking introduced from the north through contacts with Central Asia and Persia [8]. Arab Paper
The Arabs, in the course of their eastern expansion, became acquainted with the production of the new writing material reaching Samarkand. Subsequently, paper-mills were set up in Baghdad, Damascus, Cairo, and later in the Maghreb. Having no paper mulberry trees and using screens made of reed, the Arabs made thin sheets of poorly beaten rag pulp and coated them on both sides with starch paste (from wheat or rice) which could be colored. This gave Arab paper its good writing properties and its fine appearance but also made it prone to damage due to humid¬ity, crumbling or insects. In the 11th century AD, Arab papermaking knowledge spread into the Byzantine world and into medieval Europe, especially Spain (Xa¬tiva, Cordoba) and Italy (Amalfi, Genoa). Medieval European Paper
Papermakers from Genoa and Fabriano tried to improve the Arab technique. They still exploited linen or hemp rags to get pulp, but improved the beating. Water power was used to drive heavy stamping mills, huge oak trunks comprising four to six large troughs with three or four heavy wooden stampers each beating the rags in fresh circulating water. The rags were transferred from trough to trough every six hours to ensure a better degree of refining. Further improvements were molds consisting of a wooden frame with inlaid copper or brass wire, heavy screw presses, and the replacement of starch sizing by dip sizing in animal glue.
This is the origin of the division of labor leading to a considerable increase in production: Work at the vat normally involved four people: the vatman, who made the sheet using the mold; the couchman working alongside the vatman, placing the sheet on felt; the layman, who removed the moist sheets from the felts, and the apprentice, who had to feed pulp to the vat and provide vat heating. The press was operated jointly by this team. Depending on the format, up to nine reams (4500 sheets) of paper were made during a working day averaging 13 to 15 hours. The paper was dried by women hanging it on ropes in the drying loft. Apart from different sizes, three main sorts of paper were produced: writing paper (for letter and chancery use), printing paper (mostly unsized) and cheap wrapping paper (also broke, screenings), used also for drafts.
As a further consequence of the change in mold construction, watermarking was invented in medieval Italy. The real watermark, a bright figure in the paper sheet, is seen by the naked eye. In hand papermaking, it is formed by a curved wire which is sewn onto the screen of the mold; the wire reduces the thickness of the sheet, thus making the figure transparent. The watermark serves as a trademark and provides the historian with an unsurpassed dating and authenticating tool. By comparing a watermark with others of a certain date or origin, the paper historian will be able to determine the age and origin of a document or print. Shadow watermarks are produced on a mold bearing a fine, embossed woven wire, show¬ing an image like a black and white photograph. Mechanization and Industrialization
In Europe, technical progress continued. In the 16th century, glazing the sheets by hand using a glass or stone burnisher was supplemented by the use of the glazing hammer, similar to a forging hammer. Towards the end of the 17th century, a most efficient tool, the so-called “hollander” beater, supplemented or even replaced the stamping mill. As the rotating knives of the Hollander beater cut and shorten the fibers more than a stamper, the ageing of paper was accelerated. This phenome¬non is true also for the change in sizing. To improve the solubility and the penetra¬tion of the animal glue solution, alum was added, leading to acidic deterioration of paper.
Further development of printing during the 18th and 19th century led to a steeply rising demand for paper, especially for new printing grades. This and the tremendous upsurge in papermaking soon led to a serious shortage of raw mate¬rial and to regulations governing the trade in rags, to ensure the local production of paper for administrative purposes. Rags of minor quality, even cotton and wool were used, together with fillers like starch or kaolin. So systematic search for rag fiber substitutes was needed [9].
Since the 17th century, there had been some concentration of handicraft activ¬ities in big factories, consisting of several mills, which still depended on skilled papermakers organized in open guilds. The efforts made to improve paper quality (woven wire molds since 1738) and to step up production as much as possible employing local people and developing auxiliary mechanical means (rag cutter, rag digester, hollander beater, vat paddles, strainers, couching press, hydraulic press, glazing table, glazing hammer, calender) culminated in the design and construc¬tion of paper machines. Paper Machines
A Frenchman, J. N. L. Robert, built the first paper machine, patented in 1799. It was driven by one worker using a crank. The diluted pulp contained in a large vat was hurled into a wooden chest by a rotating paddle wheel and directed onto an endless wire screen of laid type. The screen bearing the forming paper web was moved forward, horizontally shaken and passed a pair of couch rolls equipped with felts. The web, still moist, was then taken by a worker and cut into large pieces which were hung on ropes to dry.
This machine was further developed in England by Bryan Donkin and by the Fourdrinier brothers. Soon, other types were developed, e. g. the cylinder machine (Bramah, 1805; Dickinson, 1809) in which a cylinder with mounted wire-screen rotates in a vat filled with pulp. Other types were the mold-chain machine (Four¬drinier, 1806) and the twin-wire machine. Flat-type and cylinder machines gained ground in the 19th century and were extended to include a dryer section (Cromp¬ton, 1820) and a reeler, somewhat later (1850) also a calender section. Steady im¬provements led to a considerable increase in production. The paper machine her¬alded industrialization. In this new situation, the small operators who were unable or unwilling to afford machines tried to survive with piece work or by producing special grades and cardboard, but they were sooner or later compelled to discon¬tinue their activities. Others had to adapt their existing buildings or set up new mills elsewhere.

The decisive step in developing the US paper industry was initiated by Joshua Gilpin (1815). Special paper machines were successfully built (e. g. the so-called “Yankee” cylinder machine), and soon the US paper production became the largest in the world. Pulping and Sizing
In European medieval papermaking, the rags were moistened and exposed to air in order to rot for weeks before beating (fermentation). This helped to dissolve dirt, yarn knots or knit links and was equivalent to a modern enzymatic fiber treatment. During beating, slaked lime was added to the slurry, which resulted in fiber swel¬ling, fiber bleaching and improved fiber separation and quality [10]. Even after washing and beating, particles of calcium carbonate and magnesium carbonate remained sticking to the fibers and got into the vat and into the paper sheet. There, they acted as a buffer, neutralizing acids and thus inhibiting the ageing of old hand-made papers.

In the 18th and 19th centuries, efforts were made to improve the efficiency of rag pulping. Rag cutting machines and rag digesters replaced old-fashioned break¬ing and boiling. The stampers were replaced by the hollander beater and later by refiners. To obtain rag substitutes on an industrial scale, in 1774, Claproth in Leipzig promoted de-inking, using a kind of bentonite. Straw was propagated as a raw material but failed because of poor paper quality (Koops, 1800). Only the invention of the stone groundwood process (Keller, 1843) and of chemical pulping (soda process: first patents, 1851: Watt, 1854: Mellier; sulfate process: Dahl 1884; sulfite process: Tilghman 1866) solved the problem of getting large fiber quan¬tities.
Dip sizing of paper bundles in a solution of animal glue was replaced by pulp sizing, using rosin and alum (Illig, 1807). The resulting acid conditions in paper¬making are in a large part responsible for the poor ageing behavior of machine-made paper until the 1980s, especially of wood-containing grades in which lignin reactions are triggered. From Industrialization to Automation and Globalization: Technical and Economic Trends of the 19th and 20th Centuries
Several partly overlapping periods may be distinguished, each marked by definite trends. Rising capital investment was needed to mechanize papermaking, and the lack of rag supply was a problem for the papermakers. In consequence the in¬troduction of a pulping section in a papermill or the construction of independent pulp mills became a priority task.

The evolution of the paper machine depended on progress in engineering and metallurgy. Until turbines replaced the venerable waterwheels, water energy was too slow and too poor to drive an improved paper machine. Even the introduction of steam engines did not help much; only when the steel quality available allowed the use of high pressure or superheated steam, did progress in papermaking be¬gin. But the problem of power transmission to the different parts of the paper machine remained. Here the introduction of electricity, permitting the installation of individual drives to every part of the machine, triggered a leap into the future: The web width was enlarged, working speed increased considerably and machines designed specifically for the production of particular paper and board grades (e. g. multicylinder machines) were developed.

Alongside the development of printing in the 19th century, new paper grades were created, together with some kind of paper specialties like punchcards, stand-up collars, tube papers, flong, pergamyn, ammunition papers, envelopes, tobacco paper, toilet paper etc. The size of a pulping plant and of a paper machine grew to such an extent, that new factory complexes had to be erected, and there were also changes in research and development, marketing, controlling and transportation. In most cases, this evolution led to commercial group building and mergers.

Since the 1980s, the use of new materials (thermomechanical pulp, deinked recycled fibers, new fillers, process chemicals and dyes) and new web forming principles (e. g. twin-wire or gap formers), neutral sizing and – the most effective change – automation have brought further progress. This led to further special¬ization in specific paper types, development of new paper grades (e. g. LWC papers, technical papers). In consequence, corporate mergers and international company groups came up with raw material supply and trading organizations of their own and unprofitable operations were shut down.
Environmental problems, documented in the 19th century already, also trig¬gered changes. New forestry principles have been introduced, fiber recycling cov¬ers more than half the fiber demand; heat recovery, closed water loops and the replacement of aggressive chemical treatments in pulping have helped to improve the poor ecological image of the paper and pulp industry.
Paper production and consumption increased from medieval times to the end of the 18th century by a factor of 50 (Fig. 1.3). Since then, paper and board have become a world-wide, large-scale commodity with exponential growth. The FAO statistics substantiate a forecast of about half a billion metric tons in 2010, of which about 2/5 will be produced in the fastest growing industrial market, Asia.