Paper Manufacture
A sheet of paper is a flattened mesh of interlocking plant fibres, mainly of wood and cotton. Making paper involves reducing a plant to its fibres, and then aligning them and coating the fibres with materials such as glues, pigments and mineral fillers. There are several stages in papermaking.
The process begins in the forest, where trees are felled and then transported to paper mills as logs. The bark has first to be stripped off the logs without damaging the wood.
After the bark is removed, the wood is pulped. The logs are first sliced into chips and then treated with chemicals in a digester. These dissolve the lignin which binds the wood fibres together. Alternatively, machines may grind the logs in water to produce pulp. The pulp is then bleached.
The next stage, mixing, is what gives paper its appearance. The bleached pulp goes to the mixer, where materials are added to improve the quality of the paper The additives include white fillers such as china clay, size for water-proofing, and coloured pigments. The mixer beats the fibres into a smooth pulp.
Liquid pulp is fed onto a mesh belt. Water drains through the holes in the mesh; the drainage is accelerated by suction. The dandy roll presses the fibres together into a wet ribbon known as a web. Belts move the web between the press rolls, which remove more water and compress the paper.
The final stage is drying. The damp web moves through the dryer, where it passes between hot cylinders and felt-covered belts that absorb water. It is then wound on reels or cut into sheets, then packaged and sent to the warehouse for distribution.
