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Wednesday, 29 November 2017

Paper Making

          Papermaking is the method of making paper, a fabric that is employed universally nowadays for writing and packing. Paper making process follows mainly three steps, they are: Preparation of fibres, Sheet formation, and Drying of paper.
          In Papermaking, at the level of completion, involves creating a dilute suspension of fibres in water and permitting this suspension to drain through fine pores of a screen, so that a mat of randomly interlacing fibres is settle down. Water is off from this mat of fibres by pressing using rolls and drying to form paper. Since the invention of Fourdrinier machine in the 19th century, most paper has been created from wood pulp because of low raw material price ascept. However other costly fibre sources such as cotton and textiles are used for high-quality papers. 
          The method of manual Paper making modified little or no over time, despite advances in technologies. The method of handmade paper manufacturing will be generalized into 6 steps: 

1. Extracting the accommodating fibre from raw material. (e.g cellulose from wood, cotton, and so on.,)
2. Converting the fibre into pulp by different beatingdown operations
3. Adjusting the properties of the paper (color, chemical, mechanical, and other) by adding some special chemicals.
4. Screening the resulting solution to form paper
5. Pressing the paper to remove water content
6. Drying of paper.
          Wood pulp is a vital product employed in the paper making process. Yet, it wasn't employed in the method till around 19th century once a German named Keller  experimened with crushing wood with a wet grindstone so as to get pulp. Probably most of the fiber used for paper nowadays comes from wood that has been intenionally harvested. The rest of the maerial comes from wood chips from sawmills, recylced newspaper, some vegetable matter. We can create stronger paper from some trees, like spruce and fir (Coniferous trees), because these species have longer and stronger cellulose fibers within the pulp. These trees are referred to as "Softwood" by the paper industry. Deciduous trees (Leefy trees like poplar and elm) are referred as "Hardwood". Due to rapidly increasing usage of paper in almost all industries, and pulp processing technology enhancements, nearly any kind of species of tree can currently be harvested and used for paper manufacturing.
          Apart from trees, some plant species like bamboo, hemp and jute etc., are appropriate for paper making. Nowadays forest area is reducing due to deforstration so in the areas without vital forests, Bamboo has been used for making paper pulp. We know that in rope making and in textile industries materials like Flax, hemp and jute fibres are unremarkably used, however they even be used for manufacturing paper. From flax some high-grade Cigarette paper is also formed.
          For some special reasons fine-grade paper is used in some purposes such as Letterheads in offices, for bank notes and security certificates. For this type of paper making process generally cotton and linen rags are employed. Rags in the name we know that a piece of old cloth, the rags are typically cuttings and waste from textile and garment mills. These rags should be dust and chemical free and also in suitable sizes to make sure that these rags should be cut into small pieces and cleaned using water and chemicals. After that boiled, and crushed before they can be used by the paper mill.
          Some other materials are also employed in paper manufacturing to give some special qualities to the paper. For coloring purpose special bleaches and dyes are used, fillers like chalk, titanium oxide, Alum and clay, and for sizing purpose sizings such as gum and starch are used.
paper making process graphic
Image Courtesy: http://www. paperonline.org/paper-making/paper-production/papermaking

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