Manufacturing of paper (paperin valmistus)

In paper manufacturing, the wood is first defibrated, or pulped, in the pulp mill. This means that the fibres are separated from each other either chemically or mechanically. After that, pulp is manufactured from the defibrated wood by drying the water-fibre mixture.

At the paper mill, the desired grade of paper can be manufactured by selecting between different types of pulp. At first the pulp is fed into the pulper. Here it is mixed with water and then fed through the end box of the paper machine onto the wire – a plastic or metal mesh – together with water. The mixture usually contains only a few per cent of fibre, while the rest is water. This allows the pulp to be spread evenly. Broke from paper manufacturing is also fed into the pulper. The broke includes the cutting waste from the dry end of the paper machine.

From the wire, the mixture is moved forward in the paper machine, which creates a continuous band of paper called the paper web. The rest of the manufacturing process is mainly designed to dry the mixture. As water is removed, the fibres bond to each other by means of electrical bonds. Once the water content of the mixture is down to about 60 percent, it begins to hold together of itself. The water content of finished paper is normally 10 percent.