From the Forest to your Desk: An Overview of How Paper is Made?

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A common practice today, the papermaking process was a revolutionary Chinese invention dating to about 105 AD and eventually spreading all over the world. Although highly technological equipment is now employed in papermaking, the underlying process continues to bear heavy resemblance to the primitive Chinese papermaking technique. <br>Papermaking, as you are probably aware, begins with trees. Often forests are grown specifically for the purpose of papermaking, and seedlings are replenished after trees are harvested. Large trees are usually made into lumber, with the remaining wood cut into small chips and used for papermaking. The cellulose fibers that make up wood are the fundamental raw material used to make paper.<br>Excess wood from the lumber industry makes up only a portion of the fiber used in papermaking. Also used as raw materials are recovered paper and roundwood. Since existing paper is comprised of the cellulose fibers found in the plant originally used to make it, paper is often mixed with new wood to create a mixture of new and reused fibers for papermaking. Roundwood is a term for wood from complete trees, though usually only smaller trees that cannot be used for lumber are used entirely in papermaking.<br>The mixture of wood chips and, in many cases, recovered paper must be broken down into individual fibers before it can be compacted and dried to form paper. During the process of pulping, cellulose fibers are separated as the chemical holding them together, called lignin, is removed in a digester. The method used to pulp paper is dependent upon the type and strength of paper being produced. There are several methods of pulping, with two common ones being mechanical pulping and chemical pulping. Mechanical pulping, in which wood is ground to separate the fibers, has suitable printing properties but results in weaker paper. Chemical pulping, which involves dissolving the lignin using a mixture of heat, pressure and chemicals, results in stronger paper that is less likely to discolor. Some applications call for the use of a combination of the two methods discussed here. Pulp is cleaned and refined, and bleached if necessary, and dyes and other additives are mixed in to give the paper the desired properties during this phase.<br>Once the pulping process is complete, water is added and the slushy substance is pumped onto a moving wire screen. On the screen, fibers become interlaced as the pulp is dried and pressed through rollers until all water has been removed. The large sheets of paper created through this process are wound into large rolls and cut into various sizes to create paper products.<br>Paper is produced for a wide variety of applications, and the papermaking process entails different techniques to produce the desired properties in the end product. Paper is carefully evaluated for uniformity of surface and color as well as how it takes ink. Though equipment and specific techniques inevitably vary throughout the industry, the underlying process of drying layers of pulp on a screen has flourished since its invention almost 2,000 years ago.

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