Paper
The back-to-school stack of loose leaf notebook paper on every child’s desk is the product of numerous chemical and engineering processes.
Credit: iStock
The core starting material for making paper is fiber, which is most often derived from wood pulp, but historically fibers from bark, bamboo, and hemp have also been used. High-quality paper may also include fibers from linen, cotton, and rag. Water is added to the fibers to create a slurry, which is then filtered through a screen to create a tangled mat. Pressing or drying the mixture removes the water to create paper, which is then put through steel rollers to make a smoother surface. The chemistry of paper is deceptively simple; fibers are held together by hydrogen bonding, a relatively weak force, which is why paper is generally easy to tear.
Water plays an important role in making paper; thus it should come as no surprise that ink, when applied to untreated paper tends to spread rather than maintaining a fine, original line. The paper used by watercolorists is intentionally left untreated. But for most uses, the desired result is a distinct, easily controlled mark. The solution is to add sizing to paper, a surface treatment which makes the paper less absorbent and more wear-resistant. Starch and gelatin were early versions of sizing until the 1800s when a process using alum was invented. Unfortunately an excess of alum resulted in an acidic paper, which reduced the long-term durability of the product.
Commercial paper-producing facilities have historically had a bad reputation for noxious smells and environmental damage, but a growing concern for environmental sustainability has prompted a number of changes in the industry. Recycling and de-inking processes are becoming a higher priority as a means of reducing the demand for virgin fiber from trees. Alternative bleaching agents such as hydrogen peroxide and chlorine dioxide are being substituted for chlorine, the traditional pulp bleaching agent used to make white paper. The paper tissue industry that produces paper napkins, facial tissue, wrapping tissue, toilet paper, and paper towels has been particularly active in reducing their environmental footprint by using recovered fibers as nearly 50 percent of their raw materials, by decreasing their energy requirements by 16 percent through improved processes, and by using biofuels to produce approximately half of their energy.
More information about paper may be found at http://www.tappi.org/paperu/all_about_paper/earth_answers/earthanswers.htm and the process of making paper is explained at http://www.forestprod.org/cdromdemo/pf/pf8.html