Pine to Paper

The paper trail: from the age of dinosaurs to the digital era

• Earth’s first papermakers
True paper requires a chemical interaction between its fibers. By that standard, insects such as paper wasps, which make tidy umbrella-like nests, and baldfaced hornets, which make football-sized ones, take the honors as earth’s first papermakers. These insects chew wood and plant fibers into a pulp. Proteins in their saliva become the glue that links the cellulose strands together, fashioning a highly moldable matrix that is light, stiff yet resilient when it dries. While the dates of their origin are in question, we do know that waspish insects found trapped in amber date back at least 110 million years.

• Mankind’s first papermaking
The ancient Egyptians, Greeks and Romans first mimicked such techniques around 3,000 B.C. They stripped off the outer bark of papyrus—from which we derive the word "paper"—and beat the marsh plant’s soft pith to break up the fibers. Squeezing and drying took several more days. The result was a tough, durable writing surface, as expensive to buy as it was labor-intensive to make. But this process did not create the chemical bonds that the wasp had achieved.

• The invention of real paper
The creation of actual paper is fixed some three millennia later, around A.D. 105. The historical record describes a courtier named Ts’ai-Lun who practiced papermaking techniques in the Hunan province of China. His recipes remained closely guarded secrets for at least a few hundred years, but the ingredients likely included cotton rags as well as mulberry and hemp. That innovation qualifies Ts’ai-Lun’s material as the first modern paper.

• The secret escapes east to west
The secret reached Korea, then Japan in A.D. 610, and followed silk and trade routes west. The Arabs likely acquired the technique in the Samarkand region of Uzbekistan around A.D. 750—as the story goes, they captured Chinese papermakers in battle and extracted a demonstration. Because Arab regions lacked good supplies of wood or other fibrous plants, their cultures developed paper made almost entirely from textile scraps. Although these papermakers did not beat the cloth very finely by today’s standards, they achieved a smooth writing surface by coating both sides with starch paste. The first paper seen in Europe was of Arabian manufacturer. Before then, Europeans used parchment and vellum made from the skins of sheep and other animals.

• Medieval innovations
Starting in the 1200s, Italians began to advance the development of paper. Craftsmen, primarily in the regions of Fabriano and Amalfi, furthered the Arabian rag technique: applying a stamping mill, using advances in wire production to make drain screens of mesh, building a paper press. Eventually paper eclipsed parchment and vellum, advancing literacy by making the written word lest costly and more accessible. By the mid-1400s, we began to see movable type, the printing press and machine-produced books including the famous Gutenberg Bible in 1455.

• Making paper from wood
The papermakers’ demand for cotton rags outpaced the supply by the early 1700s. That was when Réné de Réaumur, a French chemist and naturalist, is said to have reasoned that if wasps could make paper from wood, so could people. His and others’ research contributed to pulping techniques that redirected the paper industry by the mid-19th century. Within 80 years, Charles Herty had applied the process to southern pines.

Perfecting papermaking
Fine-tuning the modern papermaking process requires chemical additives.

Pulping Chemicals soften and separate fibers more gently than prolonged beating, dissolving the lignin that binds wood fibers together. Today, the Kraft process—developed by German chemist Carl F. Dahl in 1879 and named after the German word for "strong"—is one of the most common forms of chemical pulping. The wood is chipped into two-centimeter pieces, which are "cooked" in a solution of sodium sulfide and caustic soda.

Sizing Softening the cellulose fibers makes them more absorptive, which facilitates the chemical bonding that takes place during papermaking. But this softening also makes the finished product too absorptive, which feathers ink and soaks up stains. That is why sizing is added either during the pulping process or after the fibers are laid on a screen. Some variety of starch is common, developed first by early papermakers in the east. Size coats the fibers and can help protect paper from oxidation, or breakdown, over time. Sizing can even add back some internal adhesiveness that other additives can inhibit. Coating finished paper with a mixture of starch and clay, then polishing it to line up the particles, gives us glossy magazines and book covers.

Fillers Finely ground calcium carbonate, magnesium carbonate and other chalky compounds are often added to the vat to make paper more dense and opaque. Fillers could also include the colored rags, dyes or pigments that produce paper in a rainbow of hues.

Whiteners Titanium oxide, a chemical found in everything from paint to sunscreen, can be blended into the spaces between fibers. The purpose is to make the paper a brighter white. Whiteners are different from bleaching agents, which are introduced during pulping but are washed away before the fibers are screened and dried.

• A time-honored process
The watery pulp is sprayed onto a flat wire screen which moves through the papermaking machine, draining the water and bonding the fibers. Next, the web of paper is pressed between cylinders, squeezing out additional water and creating a smooth surface. Then the paper is dried by heated cylinders and may be coated before removal from the paper machine. The finished paper may be supplied in rolls or polished or embossed and cut into sheets.

Today, new types of laser and digital photo paper meet the demands of the information age. But, at its root, the fundamental process of papermaking is still the same: the bonding of cellulose, a polymer whose long chains support plant cell walls.

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