Jonathan M. Bloom – Saudi Aramco World May/June 1999 – Vol. 50, No. 3, Sunday 2 May 1999
Paper in One Paragraph
Paper owes its distinctive strength and flexibility to the way the cellulose fibers it is made of are chemically and physically bound together in the papermaking process. In traditional papermaking, the cellulose fibers are extracted from plants, or from rags made from plant fibers, and then beaten in water to make the fibers swell and bond together into a pulp. This pulp is suspended in water, and a mat of it is then collected on a screen and drained. As the mat dries, the fibers physically intertwine and the microfibrils form physical and chemical links with each other. Paper sheets were at first formed with a floating screen, a primitive type of mould made from a woven cloth stretched on a frame onto which the pulp was poured. The pulp remained on the screen until the sheet was dry. The two-piece mould, in which the screen could be separated from the frame and which was lowered vertically into the vat containing the macerated fibers and then raised horizontally, marked a major advance in paper-making. It allowed the just-formed sheet of paper to be removed from the mould while still moist. Other sheets could then be formed in the mould while the first sheet dried. Moulds were traditionally made of smooth bamboo or flax fibers (or, in Europe, of thin brass wire) held parallel by cross-ties of silk, flax, hair or wire. Whatever the materials, paper made with th is type of screen generally displays a distinctive pattern of faint parallel lines called “laid lines,” and European papermakers quickly discovered that they could weave designs into the screen which would leave faint “watermarks” in the finished paper.
Papyrus in Two
The papyrus plant (Cyperus papyrus; its name is the ultimate source of our word paper ) is a member of the sedge family which once grew throughout the uncultivated marshes of the Nile. In Egypt, the plant could grow to a height of five meters (16′) and its stems reach a thickness of five centimeters (2″), but under less ideal conditions the plant yields only modest stems, so that the manufacture of papyrus was essentially an Egyptian industry. By the 19th century increased cultivation had destroyed the reed’s native habitat, and it had died out in the Nile Valley, although it still flourished in the Sudan. The papyrus strain currently grown in Egypt was introduced in 1872 from the Jardin des Plantes in Paris.
The first-century Roman writer Pliny the Elder described the manufacture of papyrus sheets in his Natural History, although his description is difficult to follow and has given rise to varied interpretations. Surviving papyri, however, give some indication of how sheets of writing material were prepared from the plant. (See Aramco World , July/August 1973.) The papyrus stems were cut into manageab le lengths and the outer layer removed from the pith. The pith was then sliced or peeled into very thin strips, normally one to three centimeters wide (3/8″ – 1¼”). The resulting strips could be used immediately or dried and stored, in which case the strips were soaked until the fibers loosened. In either case, the strips were then laid parallel, one by one, on a smooth surface, just touching or slightly overlapping each other. Another similar layer, with its strips running at right angles to the first, was laid on top. Pressing or hammering brought the strips together, and the fibers of the two layers intertwined. The whole thus dried into a strong and flexible sheet. Papyrus sheets were pasted end to end with flour paste to form a roll, normally about 20 sheets long. The plant juices remaining in the sheet functioned as a natural sizing, barely allowing carbon ink to penetrate the surface, and erasures could thus be made by wiping or washing away the wet ink, or by using a stone eraser to abrade the dried surface.
The image used in this article was from the Islamic Medical Manuscripts at the National Library of Medicine, go to: http://www.nlm.nih.gov/hmd/arabic/catalog_tb.html