My Science School

When oil was struck for the first time in the Forties Field under the North Sea in 1969, it led to the discovery of at least 350 million tons of oil. But how is oil actually won from beneath the sea or the land?

Oil wells are drilled with special cutting tools, known as drill bits, which spin round to chip away at the rock. The steel, or diamond-studded steel drill bit is at the end of a strong steel pipe called the drill string, which is rotated either by a motor at the surface or by a turbine down the hole.

The rock chippings are carried upwards and out of the hole by pumping a material known as ‘mud’ down through the drill string. It is not real mud, but a combination of chemicals and water which brings up the chippings and prevents the drill bit from becoming too hot from friction.

As the hole gets deeper, fresh sections of drill string have to be added – usually in 30ft (9m) lengths. At the top of the drill string is the Kelly, which fits into a rotating table on the floor of the drilling derrick, like a nut fits a spanner. To fit a new section, the drill string is lifted up enough to remove the Kelly, then the new section is attached to the top of the drill string before the Kelly is replaced – allowing drilling to continue.

From time to time – every few hours, or every few days, depending on the rock – the bit itself has to be replaced. Then the entire drill string has to be pulled up, separated into 90ft (27m) ‘stands’, each consisting of three lengths, and stacked vertically on the derrick. When the bit finally emerges and is replaced with a new one, the whole string has to be reassembled and lowered down the hole again. The process, known as a ‘round trip’, can take up to ten hours if the well is already deep.

To prevent the hole caving it, it is lined with casing – heavy steel pipes are lowered in as drilling proceeds and cement is pumped around them to fix them in place. The casting gets progressively narrower as the well deepens. A 15,000ft (4500m) well may have 30in (760mm) diameter casing at the surface, decreasing in steps to 7in (180mm) at the bottom.

If the drill strikes oil, the weight of the mud ensures that the oil cannot escape, but there is an additional safeguard – a special valve called a blow-out preventer is fixed to the top of the casing.

The rate at which a well is drilled depends entirely on the type of rock. It can be as slow as 12in (300mm) an hour in the impervious cap rock, or as fast as 200ft (60m) in soft, sandy rock.

When oil is found, a whole series of production wells has to be drilled to bring it to the surface.

Offshore and in difficult terrain, the first step is to drill a number of wells designed to reach all corners of the oil-bearing rock. This can be done from a single derrick by angling the holes to different parts of the oil field. In a large field, several derricks or drilling platforms may be used, each drilling directionally according to a plan so that the whole area is exploited.

When the production wells have been drilled and lined with casting, a perforating gun is lowered down them to drive explosive charges through the casing and cement and into the rock beyond – allowing the oil to get into the reservoir rock to displace the oil towards the production wells.

Later, electrical or mechanical pumps may be used. But even with the help of such techniques it is seldom possible to extract more than about 30 to 50 per cent of the oil in a field.

 

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Most of the Earth’s water (around 97%), is contained in the oceans. The polar ice caps hold a further 2%. The remainder (just 1%) is continually recycled through a natural process called the water cycle. The heat of the Sun evaporates water from the sea, lakes and rivers. This produces water vapour, which is held in warm air in the atmosphere. When the vapour moves to a cool area it condenses, forming clouds, and eventually falls to the surface as rain, hail or snow. This waters the land and feeds the world’s water supplies. Most of the water then returns to the oceans, and the cycle continues.

Evaporation, one of the major processes in the cycle, is the transfer of water from the surface of the Earth to the atmosphere. By evaporation, water in the liquid is transferred to the gaseous, or vapour, state. This transfer occurs when some molecules in water mass have attained sufficient kinetic energy to eject themselves from the water surface. The main factors affecting evaporation are temperature, humidity, wind speed, and solar radiation. The direct measurement of evaporation, though desirable, is difficult and possible only at point locations. The principal source of water vapour is the oceans, but evaporation also occurs in soils, snow, and ice. Evaporation from snow and ice, the direct conversion from solid to vapour, is known as sublimation. Transpiration is the evaporation of water through minute pores, or stomata, in the leaves of plants. For practical purposes, transpiration and the evaporation from all water, soils, snow, ice, vegetation, and other surfaces are lumped together and called evapotranspiration, or total evaporation.

Water vapour is the primary form of atmospheric moisture. Although its storage in the atmosphere is comparatively small, water vapour is extremely important in forming the moisture supply for dew, frost, fog, clouds, and precipitation. Practically all water vapour in the atmosphere is confined to the troposphere (the region below 6 to 8 miles [10 to 13 km] altitude).

The transition process from the vapour state to the liquid state is called condensation. Condensation may take place as soon as the air contains more water vapour than it can receive from a free water surface through evaporation at the prevailing temperature. This condition occurs as the consequence of either cooling or the mixing of air masses of different temperatures. By condensation, water vapour in the atmosphere is released to form precipitation.

Precipitation that falls to the Earth is distributed in four main ways: some is returned to the atmosphere by evaporation, some may be intercepted by vegetation and then evaporated from the surface of leaves, some percolate into the soil by infiltration, and the remainder flows directly as surface runoff into the sea. Some of the infiltrated precipitation may later percolate into streams as groundwater runoff. Direct measurement of runoff is made by stream gauges and plotted against time on hydrographs.

Most groundwater is derived from precipitation that has percolate through the soil. Groundwater flow rates, compared with those of surface water, are very slow and variable, ranging from a few millimetres to a few metres a day. Groundwater movement is studied by tracer techniques and remote sensing.

Ice also plays a role in the water cycle. Ice and snow on the Earth’s surface occur in various forms such as frost, sea ice, and glacier ice. When soil moisture freezes, ice also occurs beneath the Earth’s surface, forming permafrost in tundra climates. About 18,000 years ago glaciers and ice caps covered approximately one-third of the Earth’s land surface. Today about 12 percent of the land surface remains covered by ice masses.

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Mineral water comes from natural sources of water beneath the ground. The types of minerals in the water will depend on the type of rock over which the water has been running —different areas produce mineral water containing different types of minerals. Calcium, sodium and sulphur are examples of minerals commonly found in mineral water. Sources of mineral water are most often in mountainous and hilly regions.

Although water covers three quarters of the world and adorns the skies in its gaseous form, the truth is water fit for human consumption is growing scarce. We all must take care to conserve and care for it as we do our greatest treasure: life.

Nevertheless, nature gives us a very special kind of water from the depths of the earth, one that has been enriched with the earth’s minerals and naturally purified through filtering during its journey underground.

Mineral water is water from a mineral source that contains various minerals, such as salts and sulfur compounds. Mineral water may be effervescent (i.e., “sparkling”) due to contained gases.

Traditionally, mineral waters were used or consumed at their sources. This was often referred to as “taking the waters” or “taking the cure.” Civilization eventually developed around these sources, and people used them for spas, baths, or wells. The term “spa” was a place where the water was used for soaking; “bath,” where the water was used primarily for bathing, therapeutics, or recreation; and “well,” where the water was to be consumed.

Mineral water comes from natural sources like wells, pure and rich in minerals. Unlike tap water that receives different treatments before human consumption, mineral water is bottled directly from the source, without adding any chemical elements. It only goes through a physical process of filtration to ensure maximum purity.

• Mineral waters can be classified according to their origin:


• Meteorological: Produced by rain, snow, and de-icing.


• Juvenile: Those that see daylight when surfacing.


• Fossil: Formed from sediments deposited on the sea floor.


• Mixed: Composed from a mixture of meteorological, juvenile, and fossil water.

Today it is far more common for mineral water to be bottled at the source for distributed consumption. Traveling to the mineral water site for direct access to the water is rare, and in many cases not possible because of exclusive commercial ownership rights. There are more than 3,000 brands of mineral water commercially available worldwide.

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Many millions of people in developing countries do not have access to clean drinking water and sanitation. In the countryside, people may be forced to use the same ponds, streams, rivers and lakes for drinking and for sewage. In cities, water supply and sewage systems are often inadequate and, in both cases, people may be exposed to serious illnesses such as malaria, cholera and yellow fever.

The United States has one of the safest public drinking water supplies in the world. Over 286 million Americans get their tap water from a community water system. The US Environmental Protection Agency (EPA) regulates drinking water quality in public water systems and sets maximum concentration levels for water chemicals and pollutants.

Sources of drinking water are subject to contamination and require appropriate treatment to remove disease-causing contaminants. Contamination of drinking water supplies can occur in the source water as well as in the distribution system after water treatment has already occurred. There are many sources of water contamination, including naturally occurring chemicals and minerals (for example, arsenic, radon, and uranium), local land use practices (fertilizers, pesticides, and concentrated feeding operations), manufacturing processes, and sewer overflows or wastewater releases.

The presence of contaminants in water can lead to adverse health effects, including gastrointestinal illness, reproductive problems, and neurological disorders. Infants, young children, pregnant women, the elderly, and people whose immune systems are compromised because of AIDS, chemotherapy, or transplant medications, may be especially susceptible to illness from some contaminants.

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In parts of the world that receive little rainfall, access to water can be difficult. In such areas, wells May be dug deep underground, or water can he piped from natural springs. Some countries even process seawater at a desalination plant. The seawater is heated, and only pure water evaporates. When it condenses, it is collected, leaving behind the salt in a concentrated form.

It has been the driest start to a summer in over 45 years in the UK. Yet, much of the country had water in reserve when it began, ensuring a continued safe supply for drinking and washing. Millions around the world are not that lucky: despite high rainfall, they go thirsty.

In some of the wettest countries in the world - where rainy days bring a lot more water than the 1248mm average that falls yearly in the UK, according to World Bank data - clean water is extremely hard to get, especially for those living in poverty.

Unlike the UK where it rains all year round, many of these countries face heavy rainfall in one season and severe drought in the next - both exacerbated by climate change - putting water resources under heavy strain.

In some regions, climate change is making water sources increasingly unreliable as flooding contaminates previously drinkable water. Yet, the problem is often not a physical lack of water: some places have significant underground reserves - known as 'groundwater' - because of abundant rainfall. Here, thirsty communities cannot get sufficient clean water because of a lack of investment in the infrastructure needed to deliver a reliable supply, indicating a lack of political prioritization.

"Not having clean water to drink is not, for most people, due to a lack of rain. For the one in nine people around the world - 844 million - who do not have clean water close to home it is usually because there is not enough investment in systems to ensure rainwater is captured, stored, treated and piped effectively."

Papua New Guinea. The impacts of climate change - rising seas and extreme weather - have tainted groundwater, meaning that even though an average of 3055mm of rain falls each year, most of the water is unsafe to drink. The number of people with access to clean water close to home is decreasing: 4.83 million people (or 63 percent of the population) do not have clean water available within a half hour trip.

Sierra Leone. Sierra Leone is twice as wet as the UK with 2427mm of rain on average each year, yet, 4 out of 10 people (42%) lack basic access to clean water. The Ebola outbreak was aided by a lack of clean water as health centres and communities struggled to maintain the high hygiene standards needed to halt the spread of the virus.

Liberia. High on the list of the world’s wettest countries with 2421mm of rainfall on average each year, a third of the population remains without access to clean water, or 1.36 million people. Liberia is still recovering from two devastating civil wars that wiped out much of the country's infrastructure and the 2014 Ebola outbreak demonstrates the urgency to rebuild. 8 in 10 people don't have toilets and go out in the open, risking contaminating water sources, many of which are already at risk from industrial and mining pollution.

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Harmful bacteria that may cause serious diseases and death need to be removed from water before it can be used for domestic purposes. Dirt particles are removed because they can wear away pipes or damage industrial equipment.

Water purification, process by which undesired chemical compounds, organic and inorganic materials, and biological contaminants are removed from water. That process also includes distillation (the conversion of a liquid into vapour to condense it back to liquid form) and deionization (ion removal through the extraction of dissolved salts). One major purpose of water purification is to provide clean drinking water. Water purification also meets the needs of medical, pharmacological, chemical, and industrial applications for clean and potable water. The purification procedure reduces the concentration of contaminants such as suspended particles, parasites, bacteria, algae, viruses, and fungi. Water purification takes place on scales from the large (e.g., for an entire city) to the small (e.g., for individual households).

Most communities rely on natural bodies of water as intake sources for water purification and for day-to-day use. In general, these resources can be classified as groundwater or surface water and commonly include underground aquifers, creeks, streams, rivers, and lakes. With recent technological advancements, oceans and saltwater seas have also been used as alternative water sources for drinking and domestic use.

Clean water is essential for every human being, for drinking, cooking and other daily uses purposes like bathing, brushing, washing clothes etc. It not just makes our life healthier but also fulfills the hygiene purpose.

The regular tap water being supplied in your home might seem clear but possess various sorts of health-affecting bacteria and viruses such as fluorine compounds, chlorine, mercury, lead, pesticides and other types of waste particles.

And its consumption can lead to serious health issues, and sometimes the result can be massively harmful. As per the research contaminated water lead the diseases like- diarrhea, cholera, dysentery, typhoid, and polio, and is estimated to cause 502 000 diarrhea deaths each year.

Water is a limited resource which is chemically treated to obviate various types of harmful viruses or bacteria available in it, that makes approx. 1.1 million ill each year (according to the research) and this is the core reason why water purification is necessary. Since your family’s health is in your hand, you must be very careful with the kind of water they are consuming for their day to day uses.

Several sorts of chemicals and viruses in unfiltered water can increase the chances of some kind of cancer risks. Thus, eliminating these chemicals can help you get rid of such cancer risks. Besides that, pure water also keeps things moving in your digestive tract. It helps to push food through and get you healthy digestion.

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All living things depend upon water for their survival; life on Earth would not exist without it. A clean supply of water is essential for people, not only to drink but for sanitation and health reasons. There is plenty of water on Earth, but not everyone has access to the same amount. Demand for water is always increasing, and supplies in many parts of the world are overstretched. In such areas, supplying fresh water can be a time-consuming and expensive business. For many people, a safe, regular supply of water is taken for granted but without it life, and indeed industry, would come to a halt.

Water is a life giver - even a life creator. It lies at the basis of our understanding of how life works. It also lies at the basis of how we understand our own personal lives. Of the four (or five) basic building blocks of life, water is the only one with a visible cycle, which we call the hydrologic cycle. Fire has no cycle that we can see, either do earth or air. And we don't understand spirit (the ether) enough to know if it does or not. Water is a constant reminder that life repeats.

The hydrologic cycle works as follows: From its most usable state, water evaporates and joins the air as water vapor. When the air cools, the vapor condenses and creates clouds, which help block heat from the sun. Colonies of the ice-nucleating bacterium, P. syringe, blown into the clouds by wind, help them to precipitate and fall as rain, snow, or hail. Much of the precipitation is stored on land as groundwater and lakes, snow and ice. From there water flows to the sea, where it joins the "primordial soup" again as ocean, ready to start the cycle anew.

Here are many of the roles that water provides both for the earth and for humans—that help produce the abundance of life we see around us every day. Without even one of these our lives would be far different.

Without water the air and earth would vacillate between extreme hot and extreme cold every day, everywhere, with a gradual increase in temperature as time goes on. Part of the problem with global warming could be that we are using up too much land water and throwing rain away into the sea.

In addition to being the soup from which life emerged, the ocean and other water bodies act as home for more life than what lives on land. Mammals, fish, birds, insects, trees, plants, algae, krill, and many other forms of life either live directly in water or are wholly dependent upon it for survival. This includes the tiny iceworms, copepods, and diatoms that inhabit trillions of minuscule tunnels in icebergs and their undersides, providing food for whales and fish that migrate to the poles to eat.

Water and carbon dioxide are the two key components of plant photosynthesis, which is how plants make their food. Bees use water to make honey, flowers use water to make nectar, trees use water to make pitch, spiders and snakes use water to make venom, and termites mix saliva with mud to make their homes. Humans use water to make paint, dyes, inks, all kinds of drinks, and we bottle it straight. We use it for paper, fabrics, food processing, chemical compounds, and the manufacture of hundreds of other products essential to modern living.

Without water, plants and many insects and arthropods could not survive, nor would humans have developed the foods and industries we have.

To humans, as creators of our own lives, water is our servant. We use it to grow crops and livestock, to cleanse and keep ourselves healthy, to stimulate ideas for products, and to transport those products. We use its cycles to remind us that our own lives also work in cycles.

But if we abuse water, like masters have a tendency to do with servants, if we don't care for it and preserve it, we will end up destroying ourselves. We need the rain forests, the swamplands, the open rivers and lakes, the estuaries, icebergs, snow tops—water in all its natural forms we need. And so does the rest of life.

If, instead of commanding it, we could conceive of ourselves as a partner or an intelligent component of water's own rain and storage cycle, it might encourage us to be more respectful of what water can do and more careful of the way we utilize it.

With water, we thrive. Without water, there is no life. We must learn to value, conserve, and take care of the water we have.

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Water is supplied into most homes by underground pipes. It starts its journey in a lake or man-made reservoir and passes through a process of purification before Coming out of the tap in your home.

Collection

The water that flows from your tap is collected from the skies and they fall in the form of snow, rain or hail. The water from the sky goes through the process of collection, storage, cleaning until it is safe enough for drinking. Once the water is safe for drinking then it gets pumped to pipes and flows out of your tap. Other sources of water are deep wells, reservoirs, streams and rivers.

Cleaning

The water that is collected goes through the cleaning and treatment process. The first step in the cleaning process is when the water passes through a large sieve that captures and takes out the debris and dirt from the water. The water goes through a combined physical and chemical process to get rid of the impurities that are left in the water.

Any remnants of bacteria or germs are completely removed to make sure that the water is safe for drinking. The bacteria are removed through the disinfection process using ozone, chlorine or with ultraviolet treatment.

Storage and Delivery

Once the water is thoroughly clean, it is transferred from the water treatment facility to the storage tanks that are covered. The water storage tanks are placed on higher grounds so that there is adequate pressure for the water to flow from the pipes and out of the faucets.

The water mains transport the water up to a point outside your home. The water is then transported into your home by the service pipe that is connected to the valve. The valve is often located under the pavement and it is used to turn off the water when there are maintenance checks or repairs.

Another valve can also be installed inside your home particularly under the kitchen sink. The valve inside your home is used to turn off the water when your indoor plumbing needs repairs.

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Glass is one of the world's oldest man-made materials. It is made from sand that is heated, mixed with other materials, and then shaped as it cools. Glass is easily shaped, cheap to make and easy to recycle over and over again. It has a huge range of used from buildings and optical instruments to bottles and glasses. Modern communication systems rely heavily on fibre-optic cables, which are made from very fine glass fibres.

Glass is a non-crystalline, often transparent amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, optics, and optoelectronics. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide (CaO), also called lime, and several minor additives.

Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. Glass can be coloured by adding metal salts, and can also be painted and printed with vitreous enamels. These qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows.

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Iron has been extracted from iron ore since around 1500BC. Most iron is now turned into steel because this is a much more flexible metal. Steel is made by removing more carbon from the iron and adding other metals, depending on the type of steel that is being produced. Steel is made in an oxygen furnace. Molten iron mixed with scrap steel k poured into a furnace and oxygen is blown over it. The oxygen mixes with the carbon and removes it in the form of carbon monoxide.

Steel is iron that has most of the impurities removed. Steel also has a consistent concentration of carbon throughout (0.5 to 1.5 percent). Impurities like silica, phosphorous and sulfur weaken steel tremendously, so they must be eliminated. The advantage of steel over iron is greatly improved strength.

The open-hearth furnace is one way to create steel from pig iron. The pig iron, limestone and iron ore go into an open-hearth furnace. It is heated to about 1,600 degrees F (871 degrees C). The limestone and ore form a slag that floats on the surface. Impurities, including carbon, are oxidized and float out of the iron into the slag. When the carbon content is right, you have carbon steel.

Another way to create steel from pig iron is the Bessemer process, which involves the oxidation of the impurities in the pig iron by blowing air through the molten iron in a Bessemer converter. The heat of oxidation raises the temperature and keeps the iron molten. As the air passes through the molten pig iron, impurities unite with the oxygen to form oxides. Carbon monoxide burns off and the other impurities form slag.

However, most modern steel plants use what's called a basic oxygen furnace to create steel. The advantage is speed, as the process is roughly 10 times faster than the open-hearth furnace. In these furnaces, high-purity oxygen blows through the molten pig iron, lowering carbon, silicon, manganese and phosphorous levels. The addition of chemical cleaning agents called fluxes help to reduce the sulfur and phosphorous levels.

A variety of metals might be alloyed with the steel at this point to create different properties. For example, the addition of 10 to 30 percent chromium creates stainless steel, which is very resistant to rust. The addition of chromium and molybdenum creates chrome-moly steel, which is strong and light.

When you think about it, there are two accidents of nature that have made it much easier for human technology to advance and flourish. One is the huge availability of iron ore. The second is the accessibility of vast quantities of oil and coal to power the production of iron. Without iron and energy, we probably would not have gotten nearly as far as we have today.

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Ceramics are materials made from stony or earthy material taken from the ground. Some ceramics, such as pottery and bricks, are moulded into shape and then baked (fired) to make them set. Glass is a type of ceramic that is heated first and then moulded into shape. Some ceramic materials are able to with-stand very high temperatures and are used for specialist application in industry and engineering.

Ceramic materials are special because of their properties. They typically possess high melting points, low electrical and thermal conductivity values, and high compressive strengths. Also they are generally hard and brittle with very good chemical and thermal stability. Ceramic materials can be categorized as traditional ceramics and advanced ceramics. Ceramic materials like clay are categorized as traditional ceramics and normally they are made of clay, silica, and feldspar. As its name suggests, traditional ceramics are not supposed to meet rigid specific properties after their production, so cheap technologies are utilized for most of the production processes.

Ball clay, China clay, Feldspar, Silica, Dolomite, Talc, Calcite and Nepheline are the common materials used for most of the ceramic products. Each raw material contributes a certain property such as dry strength, plasticity, shrinkage, etc. to the ceramic body. Therefore, by careful selection of materials, desired properties are acquired for the final output. Powder preparation is a major consideration in the ceramic industry. Surface area, particle size and distribution, particle shape, density, etc. each have their own effect on production. Powder has to be prepared to meet required particle size, particle shape, and other requirements for a particular industry. Milling is done to get the desired particle size. Unlike in the, advanced ceramics industry the purity of ceramic powder is not an issue in traditional ceramics.

The traditional ceramics industry originated long ago. Even thousands of years ago it was a well-established practice in many parts of the world. Today there are many divisions of this industry. Pottery, tableware, sanitary ware, tiles, structural clay products, refractories, blocks, and electrical porcelain are some of the products of traditional ceramics.

Advanced ceramics are special type of ceramics used mainly for electrical, electronic, optical, and magnetic applications. This sector is different from traditional ceramics due to the fact that ceramic powder preparation is quite important. Advanced production techniques are employed to assure that the produced ceramic powders possess sufficient purity. Generally chemical reactions are used to produce the ceramic powder such as Sol-gel processing and liquid-gas reactions like NH3 gas and SiCl4 liquid to produce Si3N4. Many of these methods are very costly. Therefore, powder preparation is always a cost factor in the advanced ceramics industry.

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Trees are made up of thousands of tiny fibres. The paper-making process extracts these fibres and arranges them in a crisscross pattern. Wood is broken up into small pieces and then chemically treated to break it down into fibres. Most paper is produced from softwood trees such as spruce and pine.

Making pulp

1 Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution of



sodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.

Beating

2 The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.

Pulp to paper

3 In order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.

The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.

Finishing

4 Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.

The paper may be further finished by passing through a vat of sizing material. It may also receive a coating, which is either brushed on or rolled on. Coating adds chemicals or pigments to the paper's surface, supplementing the sizings and fillers from earlier in the process. Fine clay is often used as a coating. The paper may next be supercalendered, that is, run through extremely smooth calendar rollers, for a final time. Then the paper is cut to the desired size.

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