Paper

Paper (also called xaanshi) is a thin, light material made from cellulose fibers. Cellulose is a basic component of plant cell walls. The fibers are separated, soaked in water, and then spread over a screen; when the water is removed and the fibers are pressed, they bond together and form a thin sheet of paper.

Paper is used for writing, printing, images, packaging goods, cleaning, and various technical tasks. It has been the primary medium for recording information throughout history before electronic data storage systems, and it continues to play a significant role in education, commerce, and administration.

History

Paper itself originated in China. Before that, people wrote on papyrus (Egypt), cleaned bark called bast, wooden tablets, stone, and animal skins. The technology of papermaking spread gradually throughout Asia over centuries, then reached the Islamic world; cities such as Baghdad and Damascus became centers of papermaking. It subsequently arrived in Europe, where the invention of the movable-type printing press increased demand for paper.

How it is made

Modern papermaking begins by reducing wood or other plants into a material called pulp. Pulp can be obtained mechanically or by chemical dissolution of the fibers. The pulp is mixed with large amounts of water and passed through long machinery: the screen separates the fibers, heat and pressure remove the water, and finally the surface is smoothed. Sometimes substances are added to whiten, thicken, or give the paper properties that resist water penetration.

Types and sizes

Paper is classified by weight (measured in grams per square meter), thickness, gloss, and use. There are writing paper, printing paper, carbon paper, stiff cardboard for packaging, and tissue paper. The international ISO sizing standard is well-known, which includes A4; this is the most common size in offices and schools worldwide.

Environment and recycling

Paper mills consume large amounts of wood, water, and energy, and can produce polluted water if not managed properly. For this reason recycling is necessary: used paper is collected, contamination and ink are removed, and new pulp is made from it. However, fibers shorten each time they are reused, so recycling cannot be infinite, and new fibers must always be added.