Continuous Sheet Of Paper example essay topic

Paper is a thin, flat material produced by the compression of fibres. The fibers used are usually natural and based upon cellulose. The most common material is wood pulp from pulpwood (largely softwood) trees such as spruces, but other vegetable fiber materials including cotton, linen, and hemp may be used. A stack of 500 sheets of paper is called a ream. The edges of paper sheets can act as very sharp razors, leading to paper cuts. Manufacture Whether done by hand or with a Fourdrinier Machine, the paper making process has four simple steps: Preparation of the fibres The material to be used for making paper is first converted into pulp, a concentrated mixture of fibers suspended in liquid.

As many of these fibres are derived from natural sources, this process often requires many stages of separation and washing. Once the fibers have been extracted, they may also be bleached or dyed to alter the appearance of the final product. Forming into sheets The pulp mixture is then further diluted with water resulting in a very thin slurry. This dilute slurry is drained through a fine-mesh moving screen to form a fibrous web. A watermark may be impressed into the paper at this stage of the process.

This moving web is pressed and dried into a continuous sheet of paper. In the case of the mould process, a quantity of the pulp is placed into a form, with a wire-mesh base (or other draining device), so that the fibres are left coated on the mesh and excess water can drain away. At this time, pressure may be applied to remove more water through a squeezing action. The paper may then be removed from the mould, wet or dry, and go on to further processing. Most mass-produced paper is made using a continuous (Fourdrinier) process to form a reel or web. When dried, this continuous web may be cut into rectangular sheets by slitting the web vertically and then cutting it horizontally to the desired length.

Standard sheet sizes are prescribed by governing bodies such as the International Organization for Standardization (ISO). Further additives Raw paper that contains only pressed and dried pulp is very absorbent (for example, blotting paper), and does not provide a good surface upon which to write or print. Thus, a huge variety of additives are employed to add desired properties to the paper. These are applied in a coating called the size.

Sizing agents are often polymers designed to provide a better printing surface. Starches are very commonly used, as is polyvinyl acetate (PVA), but there as many types of polymer employed as there are types of paper. Coatings can also be applied to the surface of paper to improve the printing surface by making it smoother. The texture of raw paper is rough, and so to achieve greater smoothness, coatings consisting of latex or other binders and fillers such as kaolin or calcium carbonate are used. Glossy, silk or matte finish papers such as magazine paper (for the inside pages) are made in this way. Additionally glossy or textured surfaces can be applied using a process called calendering, in which the fresh rolled paper is run through an additional series of rollers to imprint the desired texture.

The glossy effect (for example on the covers of fashion magazines) is achieved at the end of the printing process, by adding a clear layer (like varnish) over the printing, and so is not a property of the paper. Other additives are employed to enhance various properties of the paper, the most common of which are optical brighteners used to give paper a bluer shade. 'Granite paper' is a term for paper stock embedded with extremely fine colored fibers of either cloth or paper. Drying The paper may actually be dried several times during its manufacture (dry paper is much stronger than wet, so it is best to keep the paper dry to prevent it breaking and stopping the production line).