What material is paper made of?

The microscopic structure of paper

Until the middle of the 19th century, the basic raw material for paper was linen and cotton cloth, which was used to produce good quality paper. However, the increasing demand made it necessary to use another raw material that was much cheaper and easier to obtain: wood pulp, usually soft wood such as conifers.

The wood contains cellulose, an organic material that forms resistant fibers about 2.5 mm long. Once cut down, the trees become splinters that are put into huge extractors, where they are mixed with chemicals and subjected to high temperatures and pressures, to separate the fibers and obtain the pulp.

impurities such as resin and tar are removed, the pulp is bleached and then mixed with chemicals to give it the desired colour or make it whiter. The mixture then flows through the groove of a large tank, which leads to a mobile grate, which lets the water escape and retains most of the fibers. The sheet is pressed to remove more water, and dried by passing it around steam-heated cylinders. Finally, the paper can be coated with pigments to improve its surface.

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