How and from what glass and glass products are made. Glass: what is it, types, production technology, properties, purpose

Surprisingly, when faced with glass products every day, few people think about what glass is made of. Meanwhile, the process of creating this material is quite interesting, and the range of application is very wide.

Glass manufacturing technology

The main component from which it is made is the usual quartz sand. In order to form a transparent and colorless monolith from an opaque loose substance, it is heated to very high temperatures. Due to this, individual grains of sand are fused together, and since the cooling of the glass "dough" occurs very quickly, they do not have time to return to their original shape. In addition, the composition of the glass includes soda, a little water and limestone. To obtain a colored material, metal oxides are added to the molten mass. Which one depends on the desired result. So, for example, oxides of chromium and copper give together green color, separately chromium oxide - yellow-green, and cobalt - deep blue.

The glass production technology is as follows. First, all components measured with the most accurate electronic scales, are sent to a giant furnace, where at a temperature of 1600 ° C they turn into a single mass. Then this mass is made homogeneous or, speaking scientific language, is homogenized, and all gas bubbles are removed from it. Then the glass mass will have to "bath" in a bath with molten tin, the temperature of which approaches 1000 ° C. Due to the lower density than that of the tin melt, the glass does not mix with it, but rather floats on the surface. At the same time, it cools and acquires perfect smoothness.

The thickness of the material depends on the dosage of the consumable mass that enters the bath - the smaller it is, the thinner it will turn out. When the glass fiber leaves the tin bath, its temperature drops to 600°C, but it is still hot enough to solidify. Therefore, it is cooled again by passing the glass "sheet" through a conveyor of rotating rollers until the mass cools down to 250 ° C. Cooling must be gradual, otherwise the material will crack. At the end of the conveyor, an automatic quality control is installed - revealing possible flaws in the material. The places marked by the scanner are removed at the next stage of the process - during the cutting of a single “web” into sheets of the desired size. In the process, its edge is cut off, on which a strip of gears remains.

The resulting scraps are added to a new batch of glass "dough" - thus, making glass becomes a waste-free process.

Glass characteristics

Now that the answer to the question of how glass is made has been received, it's time to talk about it in more detail. So, there are several parameters by which glasses are divided. According to their purpose, they are divided into three categories. Household - that is, those that go to the manufacture of dishes, containers, glasses and various decorations. Construction - this list includes glass blocks, double-glazed windows, shop windows, mosaics, stained-glass windows and so on. And, finally, technical, used in the chemical, engineering and other industries. The second sign by which these products are divided into five classes is the type of processing.

  • First grade. It includes items made using technologies that involve one or another glass processing.
  • Second class. Includes products that have undergone machining surfaces, such as: grinding, polishing, matting (without the use of chemicals), engraving and so on.
  • Third class. This category includes objects whose faces have been cold worked. mechanically. For example, they were rounded or faceted.
  • Fourth grade. Items that have been chemically treated, such as etched or matted with acids.
  • Fifth grade. Glasses with film or any other coatings.

Also, glass is distinguished by the texture of the outer surface. There are seven categories here, one of which includes, and the other six - glossy. Glossy surfaces can be etched, free from coatings or coated with organic film, silicone compounds, semiconductors or metal sputtering.

glass properties

One of the main properties of this material is the ability to transmit light. It is worth saying that glasses with 100% light transmission do not exist in nature. The best representatives of the transparent "brotherhood" let through about 92% of visible light, and the usual window windows - no more than 87%.

The thermal conductivity of glass, that is, the ability to conduct heat from hotter areas to cooler areas, is very low. This ability of this material creates the possibility for its use in or ovens. The density of glass, that is, the ratio of mass to volume, depends entirely on its chemical composition. So, for example, if lead enters the glass, then its density will be high. The usual window has a density of 2.5 g per cm 3 - in other words, 1 cm 3 weighs 2.5 grams.

Hardness- that is, the ability to resist the penetration of other materials, is approximately six points on the Mohs scale. By comparison, diamond, the densest material according to this definition, has a value of ten. The fragility of glass, as everyone knows, is very high, but its exact indicators can only be determined in a special laboratory.

Glass has served man for many hundreds of years, and the process of its creation is still attractive and in some ways even mysterious. It not only protects our homes from the cold and winds, but also gives great freedom for creativity - from creating stained-glass windows to blowing all kinds of objects out of it.

What is glass made from?

  1. It is better to buy in the store and not bathe.
  2. What is glass made from?

    Paradoxically, GLASS is a solidified liquid.
    The main component of glass, which is included in it in most(60-70% of the volume) and defining its typical properties is SILICA SiO2 (sand, quartz, fine-grained sandstone).
    Silica is introduced into the composition of glass, in the form, for example, of quartz sand.
    In glassmaking, only the PURE varieties of quartz sand are used, in which total pollution (impurities of clay, lime, mica) do not exceed 2-3%.
    Especially undesirable is the presence of iron, which, found in the sands even in small quantities, stains the glass in an unpleasant greenish color.

    Glass can be welded from sand alone without adding any other substances to it, but this requires a very high temperature (over 1700 degrees C).
    Conventional modern stoves made of refractory clay bricks, which use solid, liquid or gaseous fuels, are not suitable for this: you have to resort to electric furnaces, the operation of which is very expensive.
    Therefore, in order to lower the melting point of sand, various additives are used...

  3. It is made from sand at high temperature and pressure.
  4. To make glass, craftsmen take: quartz sand (the main component); lime; soda; How glass is made First, quartz sand, soda and lime are heated in a special furnace to a temperature of 1700 degrees above zero. The grains of sand are interconnected, after they are homogenized (turns into a homogeneous substance), the gas is removed. The mass is dipped into molten tin with a temperature above 1000 degrees, which floats on the surface due to its lower density. The thinner the mass entering the tin bath, the thinner the glass will be at the exit. Glass making The final touch is gradual cooling.

    Soda helps to reduce the melting point by 2 times. If it is not added, the sand will be very difficult to melt, and, accordingly, to connect the individual grains of sand to each other. Lime is needed so that the mass endures water.

  5. Quartz sand, lime and soda
  6. Well, actually from quartz sand
  7. Glass is obtained by melting a mixture of sand and other mineral components, which - depends on the brand of glass. For example, crystal glass, from which decorative tableware is made, contains a significant amount of lead. When pure quartz sand is melted, quartz glass is obtained - it is very refractory and viscous in the melt, so that it does not even turn out to be transparent due to the air bubbles remaining in it. It has a meager coefficient of thermal expansion - if it is heated to red and put into water, it will not crack. It is used in the manufacture of laboratory glassware, glass heating elements for laboratories and industry, etc. To obtain optical quartz glass that transmits ultraviolet, rock crystal is melted - this, like quartz sand, is pure SiO2, but coarse-grained, which is rare in nature.

    To Vasilchenko's answer. Previously, uranium glass was made for the manufacture of decorative dishes - an amazing yellowish-green color, products from it can be seen in Moscow in the Kuskovo Museum. With the discovery of radioactivity, the production of such glass was stopped.
    To protect against radioactive radiation, lead glass screens are used - it contains even more lead than decorative crystal, and has a yellowish tint. Kinescopes for monitors are made from the same glass - to protect the PC user from the flow of electrons from the "electron gun" of the kinescope.

  8. Ordinary glass contains about 70% silicon dioxide in its composition, which is found in the same form in quartz, and in its polycrystalline form, sand. Glass composition

    Pure silica (SiO2) has a melting point of approximately 2000 degrees and is mainly used to make glass for specialty instruments. Usually, two more substances are added to the mixture to simplify the production process. Firstly, it is sodium carbonate (Na2CO3), or potassium carbonate, which lowers the melting point of the mixture to 1000 degrees. However, these components contribute to the dissolution of glass in water, which is highly undesirable. Therefore, another component of lime (calcium oxide, CaO) is added to the mixture to make the composition insoluble. This glass contains about 70% silica and is called soda-lime glass. The share of such glass in the total production is approximately 90%.

    Just like lime and sodium carbonate, other ingredients are added to ordinary glass to change it. physical properties. The addition of lead to glass increases the refractive index of light, significantly increases the brilliance, and the addition of boron to the composition of the mixture changes the thermal and electrical properties of the glass. Thorium oxide gave glass a high refractive index and low dispersion, which is necessary in the manufacture of high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern products. Iron additives in glass are used to absorb infrared radiation (heat).

    Metals and their oxides are added to glass to change its color. For example, manganese is added in small amounts to give the glass a green tint, or at higher concentrations, the color of amethyst. Like manganese, selenium is used in small doses to discolor glass, or in high concentrations to impart a reddish color. Small concentrations of cobalt give the glass a bluish tint. Copper oxide gives turquoise light. Nickel, depending on the concentration, can give the glass a blue, purple or black color. Depending on the composition of the glass, its color can be influenced by heating or cooling. #9679; Chemical composition, % :
    SiO2 - 72.2
    Al2O3 - 1.7
    CaO+MgO 12.0
    Na2O+K2O 13.7
    SO3 - 0.3
    Fe2O3 - 0.1

  9. Made from quartz sand.
  10. From silicon, by electrolysis.

Glassware, windows in houses and much more - for us today these are familiar furnishings. However, many centuries ago, glass goblets were fabulously expensive, and they could only be found on the tables of the richest and noblest nobles.


What is glass made of, and how did people learn to make it?

History of the invention of glass

Glass has been known for at least two thousand years. The ancient Roman historian Pliny described the incident as a result of which it was invented. According to his version, once sailors carrying soda on their ship landed to spend the night on a shore covered with pure golden sand.

They lit a fire to cook dinner and keep warm. By chance, one sack of their cargo burst open and spilled the soda into the fire. At night it began to rain, washed away the ashes and firebrands, and the sailors saw a shining glass surface in place of the fire.

Glass making components

Is this how glass was actually invented, or, as another version says, it turned out in the course of experiments with firing clay pots- but people have mastered the secret of its preparation for a long time.

In order to make glass, three main components are required.

Quartz sand- This is pure river sand, consisting of silicon oxide. The proportion of sand in the mixture for melting glass is about 75%. It melts at very high temperature: It needs to be heated to 1700 degrees Celsius. The transparency and quality of future glass products largely depend on the quality of the sand. Venetian glassblowers, who made the most famous in medieval Europe Murano glass, sand was specially brought from the province of Istria, and for Bohemian glass, craftsmen crushed pieces of quartz into fine sand.

Soda (or potash) needed to melt the sand at a lower temperature. By adding soda to the sand in the right proportion, the heating temperature of the glass mixture is reduced by almost half.


During heating, soda decomposes to sodium or potassium oxide, which serves as a melting catalyst. In ancient times, it was obtained by leaching ash after burning algae or conifers tree. The proportion of soda in the mixture for glass is about 16-17%.

Lime, or calcium oxide, makes glass insoluble by most chemical substances, strong and shiny. For the first time, Bohemian glassblowers began to add it to glass in the seventeenth century, using limestone or chalk for this.

In addition, today sodium sulfate, talamite and nepheline syenite are added to the mass for making glass. To obtain multi-colored glass, oxides of various metals are used as additives: copper, iron, silver, etc.

Stages of sheet glass production

All the ingredients from which glass is made are loaded into a furnace and heated until a liquid homogeneous mass is formed.

The molten mass is loaded into a homogenizer and mixed until completely homogeneous.

The glass mass is poured into a long container containing molten tin. On its surface, the glass is poured in an even layer of the same thickness, gradually cooling down.

The frozen glass tape enters the conveyor, where the thickness control and cutting into standard pieces of glass is carried out. Cropped jagged edges and rejects that have not passed quality control are sent for remelting.

Finished sheet glass passes the final quality check and is sent to the warehouse finished products.

Similarly, glass is made for the production of dishes, measuring instruments, Christmas decorations and other products. The composition of the glass may vary depending on the properties it is intended to have.

In addition, to increase strength, it can be subjected to a hardening procedure, acquiring the ability to withstand strong blows along the surface.


Popular today duplex and triplex glass, glued special formulations two or three layers of thin glass. However, the basis of each of them is golden quartz sand, baking soda and ordinary lime.

Instruction

First, technologists select the components from which glass will be made for specific needs. Quartz sand, sodium sulfate, soda ash, dolomite and some other additives are used as starting materials. All components are carefully measured, because from right choice proportions will depend on the quality of the glass mass.

Broken glass is also added to the hopper with the original components. In the manufacture of glass mass, there is usually surplus and waste, which also goes into business. They are crushed and fed into a common container, where all materials are mixed to a relatively homogeneous state. The mixture is now ready for the next processing step.

From the bunker, the initial components enter the gas furnace. The temperature inside this device reaches 1500°C. Under the influence of such an amount of heat, the components of the future glass melt and turn into a transparent mass. The resulting composition is thoroughly mixed so that the substance becomes completely homogeneous. The whole process is constantly under the control of the furnace operator, assisted by automation.

At the next stage of processing, the glass mass enters special containers. They resemble large bathtubs filled with liquid tin. Distributed over the surface of this metal, the future glass does not sink, but turns into a thin sheet material with an almost perfectly even surface. To give the sheets the desired thickness, the glass is passed through rolls certain size.

Gradually the glass ribbon cools down. After leaving the tin bath, the temperature of the material decreases to about 600°C. Now the tape is fed onto a long roller conveyor and reaches a special device where the glass is tested for sheet thickness. The control accuracy is very high and can reach hundredths of a millimeter. The identified marriage is returned to the stage primary processing.

The long and continuous glass strip is subsequently cut into standard sheets using a wear-resistant tool. At the same time, uneven edges of the sheet are trimmed. The waste generated during cutting is crushed and fed into the bunker; these fragments are involved in a new cycle of glass production. In fact, all production becomes waste-free.

The final stage of the entire process is the final quality control of the glass. Fluorescent lamps come to the aid of inspectors, which make it possible to detect even imperceptible defects in fragile material. The sheets that have passed through the control area are sent to the warehouse, where they are stored in a vertical position until they are shipped to the consumer.

Why do we need furnaces for glass melting? The fact is that in order to make something useful out of glass, you must first melt it, and it melts at temperatures of neither more nor less, 1400-1600 ° C.

The raw material for the manufacture of glass is mainly quartz sand (silicon oxide SiO2)


Quartz sand

To give the glass the necessary properties, quartz sand is mixed with various additives, mainly limestone (the one that is shell rock, from the facades of buildings), feldspar, dolomite, soda and dyes (metal oxides)


Limestone


Feldspar


Dolomite

Such additives in glass can be up to 20-30%. In general, the more additives, the lower the viscosity of the melt (roughly speaking, it is “fluid”) and the lower the melting point, i.e. it is easier to process, for example, blowing bottles, etc. is already possible at 800 ° C. But it can be different: if, for example, boron oxide is added to the mixture, borosilicate glass will come out, heat-resistant and resistant to temperature extremes - to the delight of housewives. Glass made of pure silicon oxide will turn out to be refractory; in order to blow something out of it, it will be necessary to heat it up to 1600 ° C.

In general, we sorted out the raw materials. Everything that is needed is thoroughly cleaned, crushed (usually special concentrating factories / productions are engaged in this), mixed and poured into a glass furnace through a special window. Inside the furnace in a huge pool, almost infernal fire takes over and turns sand into liquid in a few hours.

Flame inside the oven.

By the way, stoking such a furnace to desired temperature- a difficult, long, and most importantly, expensive process (how much fuel is needed to heat up such a huge fool for 2-9 thousand tons of glass!) Furnace service is only interrupted a couple of times for cold repairs.

Naturally, the mixture does not melt all at once, but gradually; as it melts, it mixes, air bubbles come out of it. What has already melted well is collected at the bottom of the pool (the density of the melt is higher) and, according to the law of communicating vessels, flows under the wall passing through the pool to another part of it, away from the flame and the mixture that has not yet been melted.

Here the temperature is slightly lower, and the liquid glass from here enters the next, working bath outside the furnace, and from there it goes for processing. To obtain, for example, sheet glass for windows and mirrors, it is cast and rolled almost like metal.

In order to obtain a perfectly flat surface, in modern factories, molten glass is first poured into a pool full of molten tin, and it, the glass, floating on the surface of the tin, is distributed over it in a uniform thin layer and cools from about 1000 to 600 ° C, so the so-called float glass (float-glas).

As I said, this process is continuous, and the output after cooling is an endless glass ribbon. But before it is cut into pieces, the surface is heated again with gas burners: in this way, microcracks are sealed, which still form even despite gradual cooling due to the difference in stresses inside the glass during hardening. As a result, the glass comes out especially transparent.


Float glass production

The old technology, used in Soviet factories, provided for the vertical drawing of a glass ribbon with intensive cooling of the mass coming from the furnace. Glass produced in this way is characterized by significantly higher optical distortions.

Well, it looks like almost everything is sorted out. In the picture, only one more incomprehensible part of the furnace remained: the regenerator. The contraption is wonderful and ingenious in its simplicity. For its invention back in 1856, the youngest of the Siemens brothers, Friedrich, received the English nobility. And the point is to save fuel for the glass melting furnace by heating the air supplied to the combustion furnace. And you can save up to 40% on fuel!


The principle of operation of the regenerator

The regenerator consists of two identical shafts filled with heat-resistant ceramic assemblies, which form many small air channels inside the shafts. Air enters through the first shaft, enters the furnace through the window, mixes with fuel (gas) and burns. The hot products of combustion go through another window into the second shaft, and before going outside, the mentioned ceramic assemblies are heated. Then, as soon as they are sufficiently heated, after about twenty minutes, the air flow is let through the second shaft, it is heated in it before entering the furnace, and the exhaust gases begin to heat up the assemblies in the first shaft. Then the cycle repeats.

Outside of this story, there were various heat-resistant ceramic coatings inside the furnace (metal is not suitable for such a temperature). With them, everything is also quite entertaining: physical and chemical processes, flowing during the melting of the glass, lead to amazing formations: stalactites begin to grow inside the furnace!

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