Next time you pick up a book think "bark." Book, in French le livre and in Spanish el libro, is liber in Latin and the origin of the word library, but liber in Latin also is a word for bark. A book, therefore, is "on bark." In olden Europe, this was a correct statement, because paper was made from fibers in the bark of special dicotyledonous plants. The comparison with plants continues, because pages in a book are often referred to as leaves--in German, leaf is das Blatt--and we also leaf through books! Floppy diskettes notwithstanding, our world could not communicate effectively without paper, and our FAX machines would be useless if not constantly supplied. Besides, without paper there would be no BIO 10 full-sentence outlines, no manuals, and no multiple-choice examinations--what a tragic loss that would be!
Paper that we use is composed of many separate, overlapping fibers that are matted together and dried. Any "fiber" that is at least several millimeters long can be used, so papers have to be constructed from wood fibers (e.g., those of conifers), clusters of phloem (bast) fibers, i.e., soft fibers of dicotyledonous stems, or parts of vascular bundles of certain monocotyledonous leaves, i.e., hard fibers. Of course, very thick units produce very coarse papers, and presence or absence of lignin determines brittleness and hardness of the finished sheet.
The earliest thin sheets made from plants for writing were not manufactured from separate fibers, but it was a solid structure obtained from the monocotyledonous sedge called papyrus, Cyperus papyrus. In ancient Egypt at least 3000 B.C., craftsmen learned to pare stems of this marsh plant, which can be three or more meters tall, into long, flat strips of tissue. Strips were laid vertically, slightly overlapped, and then pressed together in a press in the sun to dry fused. Vascular bundles of the stem gave strength to this sheet. Rough spots were rubbed smooth using shell or ivory, leaving a polish and a more or less absorbent sheet. The papyrus could be coated with flour paste and sprinkled with vinegar. Soot mixed with water was used as early ink, applied with a reed sharpened to a point, or papyrus was written on with charcoal. The sheet was not brittle but very strong and flexible, more durable than paper.
Egypt was a supplier of papyrus to the ancient world, and much of the knowledge passed down to us about the neighboring civilizations, from the Near East to the Roman Empire, was deciphered from papyri. In addition to literature, investigators have found letters, accounts, notices of births and deaths, contracts, tax receipts, and all types of religious and governmental documents on papyrus. Apparently, papyrus was cheaper to use than parchment and vellum, which were made from animal skins.
Rice paper is a much different product, which comes from China and Formosa. The rice paper plant, Tetrapanax papyrifera (or Fatsia papyrifera, Araliaceae), is a shrub with very large leaves. Young stems are soaked in water to loosen the very wide, soft pith from the encircling vascular tissues. The pith, mainly parenchyma, is forced out of the stem in 12 to 18 inch pieces, then dried promptly to prevent staining and loss of luster, and finally rolled over a block, flattened, and trimmed to form scroll-like sheets 4 to 6 feet long. The white "threads" in the paper are vascular bundles present in the core.
Bark of the paper mulberry, Boussonetia papyrifera (mulberry family, Moraceae), was pounded into sheets by Polynesians to form bark cloth for clothing. In southern Mexico, bark of species from that family and closely related families Tiliaceae and Ulmaceae, particularly the pioneer tree Trema micrantha, has been used for at least 1400 years to make paper. More than 480,000 sheets of bark paper were given to pre-Hispanic royalty in annual tribute, and bark paper there was used for religious purposes and for making codices. Today bark paper is still made for Mexican folk art.
True paper, i.e., matted plant fibers, was apparently one of the great inventions in ancient China. Encyclopedias often credit Ts'ai Lun of Lei-Yang, a minor court official of Emperor Hi-Ti (Han Dynasty), as the inventor in 105 A.D., but Chinese paper fragments from the first century B.C. dispel this claim. Nonetheless, earlier Chinese writings, using vertical calligraphy (invented around 2700 B.C. by Ts'ang Chieh), are preserved on silk.
Ts'ai Lun developed a method to free phloem fibers by crushing hemp fibers (Cannabis) and the bark of paper mulberry trees in water and then soaking the fibers in wood ashes (= lye). The free fibers rose to the surface, and this tangle was placed on a silk mold and dried in the sun-the first silk screening. Ts'ai Lun was mocked for his invention, so, as the tale goes, he feigned death and buried himself alive in a coffin, having a bamboo breathing tube. When he was exhumed, Ts'ai sprang from the coffin through a paper cover. So began a belief in the magic of paper and the Oriental custom of burning joss paper over the graves of the dead. Joss paper looks like money, thereby permitting ancestors to buy their way through the After Life. Ts'ai Lun eventually committed suicide by poison during a court power struggle.
The Chinese used paper mulberry, cotton rags, old hemp fishing lines, flax, and other plant fibers to make "rag paper," which was traded westward, but the secret of papermaking was kept by them for over six centuries. In 751 A.D., an army of Mohammed clashed with imperial guards in the Battle of Samarkand, a western Chinese city (the Uzbek region, later occupied by the Soviets) just north of Afghanistan. Here there was a major Chinese papermaking factory, including materials and artisans. This operation fell then into the hands of Mohammed, who saw paper as a way to spread the Islamic faith.
By the 9th century, Arabs began making their own paper from flax stem fibers (Linum), and in the 12th century paper mills were established in several Moorish cities in Spain, e.g., Toledo and Valencia. But in Europe animal parchment was the sheet of preference by The Church, and paper was sneered at because it was "made by infidels" and one could not scrape away errors. But the invention of the printing press in 1450 required rag paper, and thereby sounded the death knell for parchment and vellum. Italy became an important papermaking center.
Soft fibers were used for most early papermaking. There were also experiments with bagasse of cane, straw, and bamboo to obtain vascular bundles for paper, and this accounts for the poor quality papers of India. Not until 1840 was wood pulp used experimentally for making paper, and this gave rise to the current industrial methods. Industrialists discovered that paper could be mass produced by using woods of conifers (e.g., pines, spruces, Douglas fir, and hemlock), which have tracheids about four millimeters in length, or dicotyledonous woods (e.g., poplar and aspen) having long wood fibers. In 1870, the New York Times became the first U.S. newspaper to use all wood paper, and today the amount of newspaper used is truly incredible. Fortunately, newspaper can be recycled.
Debarked wood is chipped and then heated in the presence of strong chemicals, which remove lignin from the cellulosic cell walls and cause maceration of the tissues, i.e., the cells become separated. Chemicals used include bisulfites, sulfides, sulfurous acid, sodium hydroxide, chlorine dioxide, and sulfates. Some techniques are stronger than others, so that the process may not totally remove lignin or impurities (Kraft paper for brown paper wrapping), or at the other extreme some chemicals remove part of the cellulose. Once the cells are essentially freed, the pulp usually is sent to a beater, which thoroughly separates the wood fibers and uniformly distributes them in a solution. Then fillers, e.g., starches, clay, talc, alum, rosin, or resin, may be added, substances that add body or weight to the paper and often fill in the minute pores. Paper with sizing allows ink to flow more evenly. The liquid pulp then proceeds to the papermaking machine, where it is poured onto the Fourdrinier screen, an endless belt of wire, which moves in two directions to insure even intermeshing of the wood fiber cells as a thin layer. Water is drained off, and all water is subsequently removed by a set of heavy rollers by using pressure and high temperature. A finish may be put on the paper just before the paper emerges on huge rolls.
The processes of papermaking use strong chemicals, so that traces of these often remain in the paper. Especially acids are harmful, and can cause book pages and newspaper to be brittle and disintegrate after many years on a shelf. Old books can be rehabilitated using a chemical to neutralize that acid and bond the cellulose, but this is a costly process. Acid-free paper is required for books and documents that can last more or less indefinitely, if kept under proper conditions of temperature and humidity. Rag paper, rather than wood-based paper, has a long life expectancy.
There is a great variety of papers, produced from a broad array of woods, soft fibers, and hard fibers, fashioned into sheets of different thicknesses and with the addition of different fillers and sizings. Some woods cannot be used to make white paper, because it is too difficult to remove their resins, which cause the paper to yellow quickly, so these are used for poorer quality papers. Newspaper is unbleached conifer paper, made from species that lack the yellowing resins in the wood. White bond and ledger paper is bleached with hypochlorite. Kraft paper, including generic brown wrap, hand towels in bathrooms, cardboard, and grocery bags, comes from conifer wood in which some lignin remains. Absorbent paper toweling and toilet paper are loosely woven and without fillers or lignin, although some paper towels are now reinforced so that the paper holds more liquid and does not disintegrate so easily. Fine stationary and cigarette papers are often made from flax, whereas Bible paper apparently is made from Cannabis (hemp, of course). Plant specimens are dried and mounted as in indefinite record on 111/2 by 171/2 inch sheets of rag paper and stored in cabinets of herbaria. Some papers, including rapid photographic papers, are impregnated with plastic. Composition and method of processing, as well as supply and demand, dictate the costs of the different types of papers.
Papermaking requires much water, so mills are located along rivers, from which the logs may also be pulled, sometimes floated from the logging area. River water must be monitored because the caustic chemicals will, if not controlled, pollute the water. Moreover, the sulfur-containing vapors from the paper mills create acid rain, which threatens the viability of freshwater lakes wherever rains can lower the pH (become more acid) of runoff. Acid rain is most conspicuous in Scandinavia, Canada, and the northern United States, the same regions that are the pulpwood and papermaking centers, although the industry is not the only one responsible for acid rain and pollution of fresh water. Most countries affected by acid rain now have very strict regulations to force papermakers to trap and detoxify emissions.