Making of paper is a process discovered in China in 105 AD during the Han Dynasty. It is typically done by pressing moist fibers of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. From China, papermaking spread out across the world and in all places it is made generally the same.
Some half of the fiber for the paper today comes from trees that are harvested for this purpose or from sawmill scraps that are residue from larger trees that are made into lumber. Other material comes from the recycled sources: recycled paper, vegetable matter and recycled rags. For stronger paper are used coniferous trees, such are spruce and fir - so called softwood, because they have longer cellulose fibers, but generally any species of tree can now be harvested for paper. Some other plants can be source of cellulose fibers like: bamboo, straw, sugarcane, flax, hemp and jute. Rags are usually made from cotton and linen and are cut, cleaned, boiled, and beaten before they are used as a material for paper. Other materials used in paper making are bleaches, dyes, chalk, clay, titanium oxide, rosin, gum, and starch.
First step in making paper is making pulp. If whole logs are used they are first tumbled in drums which will remove the bark. Then huge revolving slabs grind logs which breaks the wood into wood chips. Wood chips are cooked in a chemical solution of sodium hydroxide and sodium sulfide in huge vats called digesters. Foreign objects are removed with filters and pulp can be treated for color with bleach or colorings.
Beating is a next step in papermaking. Pulp is poured in a large tub that has machine beaters. Here are added fillers like chalks, clays, or titanium oxide which change opacity and other qualities of the finished paper like how the paper will react with various inks. For this are used so called sizings and for instance starch used as sizing makes the paper resistant to water-based ink. Rosins and gums are also used as sizing.
Special automated machines now make paper out of pulp. One of these machines is called Fourdrinier machine and was invented in England in 1807. It is loaded with pulp which is then flows to the moving belt made of fine mesh screening. Moving belt leads to a series of rollers which press the pulp from above while suction devices from below the belt drain the water from the pulp. If paper needs to have a water-mark now is the moment when that is done. After this, paper is pressed between rollers that have wool felt surface. Remaining water is removed with by passing the paper through steam-heated cylinders.
Finishing of the paper consists of wounding the paper onto large reels, smoothing and compacting of the paper by passing it through metal rollers that are called calendars which can make paper soft and dull or hard and shiny. Paper can here be treated with sizing material again. After all this, paper is cut into desired sizes.