Who invented colored glass. History of glass. Industrial glass production
✪ Ordinary Story - Glass - Story One
✪ Antique glass.
✪ Ordinary Story - Glass - Story Two
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The emergence of glass
Naturally produced glass, especially volcanic glass (obsidian), has been used since the Stone Age for cutting tools. Since such glass was rare, it became a frequent trade item. Archaeological sources indicate that artificial glass was first produced on the Syrian coast, in Mesopotamia or in ancient Egypt. Most of the oldest glassware has been found in Egypt, due to favorable climate conditions for glass, but it is possible that some of these items were imported into Egypt. The oldest glass objects date back to the third millennium BC. e. These are glass beads that may have come from the process of making metal or ceramics by accident.
In the late Bronze Age in Egypt and Western Asia (for example, Megiddo), glass manufacturing technology made a sharp leap. Archaeological finds from this period include colored glass ingots and vessels, sometimes inlaid with semi-precious stones. For the manufacture of Egyptian and Syrian glass, soda was used, which is easily obtained from the coals of many types of wood, especially halophilic plants that grow on the seashore. The earliest vessels were made by spinning ductile glass fibers around a mold of sand and clay, impaled on a metal rod. After that, by repeatedly heating the glass, they ensured that it was fused into a single vessel. Stripes of colored glass could then be applied over the original shape, thus creating ornaments. Then the mold was destroyed, and the rod was removed from the resulting vessel.
By the 15th century BC. e. glass was mass-produced in Asia Minor, Crete and Egypt. It is assumed that the technologies for the production of glass from natural materials were a carefully guarded secret, and these technologies were used only at the court of the rulers of the most powerful states. Elsewhere, glassmaking consisted of processing prefabricated glass, often in the form of ingots. Such ingots, for example, were found at the wreck of the Ulu-Burun ship off the coast of modern Turkey.
Glass continued to be a luxury item, and glassmaking seemed to disappear with the civilizations of the late Bronze Age. In the ninth century BC. e. glassmaking was revived in Syria and Cyprus, and technologies were found for the production of colorless glass. The first known "manual" for the production of glass dates back to 650 BC. e. are the tablets contained in the library of the Assyrian king Ashurbanipal. In Egypt, glassmaking was never resumed until it was brought by the Greeks to the Ptolemaic kingdom. The Hellenistic period saw the further development of glass technology, which made it possible to produce large-sized glassware, in particular tableware. In particular, a technology was developed for mixing glass of several colors, so that a mosaic structure was obtained. It was during this period that colorless glass began to be valued more than colored glass, and, accordingly, its manufacturing technologies were improved.
It has been experimentally established that it is impossible to weld glass in this way. The heat that even a very large fire will give will not be enough to form an alloy of sand and soda; besides this, there are other technological features that are in clear conflict with this version of the origin of glassmaking.
Notes
- Expedition in Ancient Anatolia. Travel notes and photos of archaeological. The History of Glass: Ancient Glass Work at Bodrum Museum
- Christine Lilyquist (1993). “Granulation and Glass: Chronological and Stylistic Investigations at Selected Sites, ca. 2500-1400 B.C.E.” . Bulletin of the American Schools of Oriental Research. 290/291: 29-94.
Before appearing on your screen, this article was converted into optical signals and transmitted at a speed of ~201,000 km / s over a fiber optic cable. The cable is based on fibers made of the thinnest glass, which is 30 times more transparent than pure water. The technology was made available by Corning Incorporated. In 1970, using the results of many years of research by scientists around the world, she patented a cable capable of transmitting large amounts of information over long distances.
If you're reading on a smartphone, don't forget to thank Steve Jobs, who in 2006 asked Corning Inc. to develop a thin yet durable screen for the iPhone. The result - Gorilla Glass - now dominates the mobile device market. Screens of smartphones with Gorilla Glass of the fifth generation do not crack after being dropped in 80% of cases (test devices fell from a height of 1.6 meters - at this level people usually hold the phone - onto a hard surface).
And that's not all. Without glass, the world would be unrecognizable. Thanks to him, glasses, light bulbs and windows became available to mankind. But despite the omnipresence of glass, there is still a discussion in the scientific community about the definition of this concept. Some consider glass a solid, others a liquid. Many questions still remain unanswered: for example, why one type of glass is stronger than another, or why certain glass blends have precisely such optical and structural properties. Add to this the existing databases of glass types, one of which contains more than 350,000 currently known types, which makes it possible to create a huge number of different mixtures. The result is a truly interesting area of research that produces amazing new products on a regular basis. Glass has had a huge impact on humanity, and it is safe to say that glass shapes the face of our civilization.
"We've been using glass for thousands of years, but we still don't understand what glass is all about," said Mathieu Boschi, a glass expert and member of the UCLA research team. As a rule, glass is obtained by heating and then rapidly cooling a mixture of several substances. For example, sand (silicon dioxide), lime and soda are used to create flat window glass. Silicon provides transparency, calcium provides strength, and soda reduces the melting point. "Rapid cooling prevents the glass from crystallizing," says Steve Martin, a glass scientist at Iowa State University.
It is because of the prevention of crystallization that glass is considered an amorphous substance - rather than a solid or liquid. The atoms of the glass strive to restore the crystal structure, but they cannot, as they freeze in place during the process of its manufacture. You may have heard that the glass in the windows of ancient cathedrals flows down over time, and therefore becomes thicker at the base. This statement is erroneous: ancient manufacturing technologies simply did not allow making even glass. But it is still in motion, albeit very slowly. The results of a study published last year in the Journal of the American Ceramic Society showed that at room temperature, the glass of an ancient cathedral would take about one billion years to move one nanometer of matter.
Humans have been making tools out of obsidian and other types of volcanic glass since the dawn of civilization, and the first man-made glass was first made in Mesopotamia just over 4,000 years ago. It was probably obtained as a by-product in the manufacture of ceramic glaze. Soon this technology was borrowed by the ancient Egyptians. The executive director of the Corning Glass Museum, Carol White, claims that the first glass objects were beads, charms, and twigs to create mosaic glass. Often, with the help of minerals, they were given the appearance of another material.
“By the beginning of the second millennium BC, artisans began to make small vessels like vases. Archaeologists have found cuneiform tablets describing the process, but they were written in a secret language designed to hide the secrets of production,” White adds.
By the time of the rise of the Roman Empire, glassmaking had become an important branch of the economy. The writer Petronius tells the story of a craftsman who appeared before the emperor Tiberius with a piece of supposedly indestructible glass. "Does anyone else know how to make glass like this?" - Tiberius asked the craftsman. “No,” the artisan replied, emphasizing his own importance. Tiberius, without warning, ordered the beheading of the poor fellow. Although Tiberius' motives are not known for certain, it can be assumed that such an invention could have destroyed the empire's glass industry.
The first major innovation in glassmaking occurred in the first century BC, when glass began to be blown around Jerusalem. Soon the Romans figured out how to make glass more or less transparent: this is how the first glass windows appeared. There was a significant shift in the perception of glass, as it had previously been valued only for its decorative properties. Instead of admiring the glass, people began to look through it. Over the following centuries, the Romans produced glass on an industrial scale, and it eventually spread throughout Eurasia.
At that time, science as such did not exist, and the glass was fanned with a halo of mystery. For example, in the fourth century AD, the Romans created the famous Lycurgus goblet, which changes color from green to red depending on the angle of the light. Modern research has shown that the incredible property of the goblet is due to the presence of silver and gold nanoparticles.
In the Middle Ages, the advanced secrets of glass making were kept in Europe and the Arab countries. In the era of the High Middle Ages, Europeans began the production of stained glass. According to Carol White, the majestic glass paintings played a huge role in the study of the catechism by the illiterate population. No wonder stained glass windows are also called bibles for the poor.
Although window panes date back to the Roman era, they were still expensive and difficult to obtain. But everything changes with the construction of the Crystal Palace for the World Exhibition of 1851. The Crystal Palace was an exhibition hall with a glass area of 93,000 square meters. m. - four times more than the UN headquarters in New York, built a century later. “The Crystal Palace showed people the dignity and beauty of window panes, it influenced architecture and consumer demand,” says Alan McLenaghan, director of SageGlass, a company specializing in tinted windows and other glass products. The Crystal Palace burned down in 1936, but a few years later window glass became more affordable thanks to the British company Pilkington, whose employees invented the technique of creating heat-polished glass by pouring molten glass mass onto a layer of molten tin.
In the 13th century, long before window panes became ubiquitous, the first glasses were created by unknown inventors. The invention helped in the fight against illiteracy and laid the foundation for the further improvement of lenses, which made it possible to see things that were previously unknown. At the beginning of the 14th century, the Venetians borrowed the achievements of craftsmen from the Middle East and Asia Minor and improved the process of creating transparent glass called "crystallo". One technique involved the careful melting of quartz pebbles along with the ashes of salt-loving plants, which provided the correct ratio of silica, manganese and sodium, which at that time, of course, was not suspected. It was vital to keep the rules for making glass a secret. Despite the high status that all glass manufacturers had, the punishment for crossing the border of the Republic of Venice for them was the death penalty. The Venetians were leaders in the glass market for the next 200 years.
Using glass of their own production, the Venetians also created the first mirrors. There are not enough words to describe all the changes that their appearance entailed. Earlier mirrors were made of polished metal or obsidian, they were very expensive and did not reflect light as effectively. New mirrors made telescopes possible and revolutionized art: with their help, the Italian sculptor Filippo Brunelleschi developed linear perspective in 1425. The consciousness of people has changed. The writer Ian Mortimer even suggested that before the advent of glass mirrors, people did not perceive themselves as separate unique individuals, the concept of individual identity did not exist.
Glass has a wide range of applications. Around 1590, Hans Jansen and his son Zachary invented a microscope with two lenses at the ends of the tube, which gave a magnification of nine times. The Dutchman Anthony Van Leeuwenhoek has taken another step forward. As a relatively educated apprentice to a haberdashery merchant, Anthony often used a magnifying glass to count the threads of fabric, and in the process developed new ways of polishing and grinding lenses, which made it possible to magnify the image by 270 times. In 1670, with the help of his lenses, Leeuwenhoek accidentally discovered the existence of microorganisms: bacteria and protists.
The English scientist Robert Hooke improved Leeuwenhoek's microscope. He is the author of the famous work Micrographia, the first book on the microscopic world with detailed engravings of previously unseen images, such as the textures of a sponge or images of fleas. "Decorated with gleaming black armour, thin and neatly built," Hooke wrote of fleas. Looking at the bark of a cork tree through a microscope, the structure of which resembled honeycombs and monastic cells, Hooke coined the term "cage". These advances shocked science and led, among other things, to the emergence of microbiology and the germ theory of disease.
The appearance of glass test tubes and pipettes in laboratories around the world made it possible to measure and mix various substances and expose them to all kinds of influences. Glass tools contributed to the development of chemistry and medicine, and also made possible the appearance of the steam engine and the internal combustion engine.
While some scientists fiddled with microscopes and beakers, others turned their gaze to the sky. It is not known for certain who invented the telescope, although the first mention of this device was found in the Netherlands in 1608. The telescope became famous thanks to Galileo, who improved the existing design and began to study celestial bodies. In the course of observing the satellites of Jupiter, he came to the conclusion that the geocentric model of the world does not make sense, which caused dissatisfaction with the Catholic Church. The Inquisition Commission of 1616 concluded that the statement about heliocentrism was "absurd and absurd from a philosophical point of view and, moreover, formally heretical, since its expressions are in many ways contrary to Holy Scripture." As you can see, glass can lead to sin.
The influence of glass on our lives is not weakening. Looking to the future, researchers hope to make an equally significant breakthrough using glass to neutralize nuclear waste, create safe batteries, and design biomedical implants. Engineers develop high-tech touch screens, chameleon glass, safety glass.
The next time you see a glass object, think about it, is it not strange that a material born of earth and fire, bound like a pond by a cover of ice, constantly in atomic purgatory, makes human life so much easier and promotes progress. Look carefully not through the glass, as usual, but directly at it, and remember how many phenomena would remain inaccessible to the human eye if we did not have material at hand that is itself barely noticeable.
It is still not known for certain how glass was invented. There are many legends associated with the invention of this material, but only one of them seems relatively plausible.
According to this version, it is an accidentally discovered material that has become a by-product of one of the most ancient crafts - the manufacture of pottery. It is known that many centuries ago clay was fired to give it strength in sand pits. In those days, reeds or dry straw were usually used to make a fire. Due to the influence of high temperatures, the sand interacted with the main combustion products, resulting in the formation of a transparent, rapidly solidifying mass. Another common version of the origin of glass is the formation of a by-product during copper smelting.
Some scientists adhere to the third version. In their opinion, the glass was formed as a result of high temperature exposure to sand and African soda. According to this legend, Phoenician merchants used to cook their food on a hearth made of African soda, set on the coastal sand. This version of the origin of glass belongs to the ancient historian Pliny the Elder.
Fundamentals of ancient glass production
Glass has a very ancient history. Most scientists have come to the conclusion that this material was accidentally created six thousand years ago. However, the opinions of experts regarding the place of its occurrence are somewhat different. According to various sources, glass originated in the Eastern Mediterranean, Mesopotamia or Phoenicia.
The first glassblowers, no doubt, were the Egyptians: it was they who created glass products in special clay containers. The fritting method was also invented at that time: hot pieces of glass were dipped in cold water, ground to dust, and melted down again. This method of making glass products has been used for many centuries. This fact is confirmed by the fritting tools found as a result of archaeological excavations. At that time, the production of glass required two furnaces: one of them was used for primary melting, with the help of the other, frits were melted.
How glass was made in ancient times
The ancient furnaces used to make glass were built from alumina and stones. Their only drawback was the high consumption of firewood. This is not surprising, because inside the furnace it was necessary to maintain a consistently high operating temperature - up to 1200 degrees, and for penetration it was necessary to melt the furnace to 1450 degrees.
Soda, ashes of various plants and sand were used as raw materials for the manufacture of glass. Many centuries ago, craftsmen learned how to make not only white, but also. In those days, it was customary to use various metallurgical slags as dyes, for example, compounds of manganese, copper and cobalt. The ancient furnace was a low vault, under which clay containers were placed for melting glass. The surrounding forests served as fuel for such stoves, so when they were completely cut down, the firebox had to be moved to another place. In ancient times, glass melting was a very laborious and time-consuming process, resulting in very high prices for glass products.
The most beautiful ancient glass
The heyday of glass-blowing production began with the Roman Empire. But after the great state collapsed, glass production developed very slowly. Subsequently, the glassblowing business was divided into two directions: western and eastern.
For a long time, the methods of manufacturing glass products remained the same, only the technique was improved. The first changes in the technique of creating glass appeared at the end of the first millennium. After a series of experiments, it was possible to partially change the raw materials, but maintain the high quality of glass products. European masters replaced soda with potash, which was obtained by leaching the ashes of coniferous and beech trees. After the replacement of raw materials, Mediterranean and European products have even more differences.
Improvement in glassblowing
The leadership in the manufacture of sheet glass belongs to German glassblowers. Back in the eleventh century, they had the idea of blowing a hollow cylinder, cutting off its bottom, and then rolling the material into a thin sheet, giving it a rectangular shape. Italian masters began to use this technique only in the thirteenth century. Of course, the quality of medieval glass cannot be compared with modern glass, but the same substances are used to this day for the production of glass products. In those days, the cost of glass was very high, so it was used to glaze the windows of palaces, churches and houses of the nobility. Having mastered the improved technology of glass production, European masters for the first time begin to make stained-glass windows, to create which pieces of colored glass are fastened together with metal alloys. By the end of the Middle Ages, Venice became the center of glass-blowing production. Glassmaking here gained incredible popularity; within a few years, more than eight thousand glassblowers worked in Venice. However, very soon Venetian glass was forced to give way to crystal, which was initially made only by English glassblowers. According to historical facts, crystal was invented by George Ravencroft, who was the first to use more advanced raw materials. Instead of potash, the inventor used lead oxide, resulting in a beautiful glass with perfect reflective properties. Moreover, crystal was easy to detail and finely engraved, thanks to which such glass soon found itself out of competition.Industrial glass production
Industrial production of glass began relatively recently - only in the nineteenth century. The founder of the automatic production of glass products was Otto Schott, whose main activity was the study of the influence of various substances on the physical characteristics of glass. Schott has done a lot of research together with Prof. Ernst Ebbi. Another scientist who made a great contribution to the automation of glass production was Friedrich Simmens. It was he who created a unique furnace, allowing several times to increase the volume of glass production. A few years later, Michael Owens invented machinery for the production of glass bottles. This innovation quickly gained popularity: by 1920, more than 200 machines of this type were already operating in the United States. One of the most important methods of glass production was vertical drawing from a furnace. The author of such an invention was the Belgian scientist Foucault. Emile Bischerois, his compatriot, decided to improve this technique by proposing to pass the glass between the rollers to obtain a uniform web. A real revolution in glass production was made by the Pilkington company, which developed the float method: from the melting furnace, the glass mass enters a container with molten tin, after which it is cooled and sent for annealing. The main advantage of this method is to ensure the same thickness around the entire perimeter of the glass sheet. In addition, the Pilkington glass did not need further processing, as it lacked various defects characteristic of products made by any other method.Glass production in Russia
Glass business in Russia arose much earlier than in all European countries. Fine glassware has been made here since the ninth century. Glass production was especially popular under Peter I. In those days, not only window glass and dishes were made, but alsoLong before today, glass making was considered a labor-intensive process, similar to the creation of a work of art. For this reason, its price was very high. During the reign of Tiberius, one of the masters created safety glass, however, by order of the emperor, he was executed, since this discovery could cause a sharp decrease in the cost of glass.
Today, everything has changed, and scientists working in this field are striving to make glass as cheap as possible.
Archaeological finds indicate that the first glass was made in the Middle East around 3000 BC. In the beginning, glass production was slow and expensive. In ancient times, glass was a luxury item and only a few could afford it.
The oldest glass items are beads and pendants, created in the pre-dynastic era in ancient Egypt. The Egyptians also knew glass mosaics. Multi-colored glass plates were heated until fused, and then stretched to obtain thin and very long strips, often depicting simple hieroglyphs. These works were notable for their amazing thoroughness of execution, but at the same time, the Egyptians never sought to achieve the transparency of glass.
In India, Korea, Japan, glass items have been found dating back to 2000 BC. Excavations show that in Russia they knew the secrets of glass production more than a thousand years ago.
It is believed that man-made glass was discovered by accident, as a by-product of other crafts. In those days, the firing of clay products took place in ordinary pits dug in the sand, and straw or reed served as fuel. The ash formed during combustion - that is, alkali - upon high-temperature contact with sand, gave a glassy mass.
Glass is considered by some to be a by-product of copper smelting. And the ancient Roman historian Pliny the Elder (79 - 23 BC) wrote that we owe glass to the Phoenician sea merchants, who, while preparing food at the parking lots, made fires on the coastal sand and supported the pots with pieces of lime, thereby creating the conditions for the formation of glass.
Indeed, the raw materials for the manufacture of glass were sand, lime and alkali - organic (plant ash) or inorganic (soda). Metallurgical slags were used as dyes: compounds of copper, cobalt and manganese.
Today, the main raw material for the manufacture of glass is calcium dioxide - SiO2, which is white quartz sand. Its main advantage, compared to other substances, is that calcium dioxide can pass from a molten state to a solid state, bypassing the crystal formation process. This makes it possible to use it to create various types of glasses. Quartz has an excessively high melting point, which is why every glass shop produces glass containing 50-80% SiO2. To lower the melting point, various auxiliary substances are added to the glass mass: lime, sodium oxide, alumina.
In the last century BC e. glassmaking developed intensively in the Roman Empire. A clear political and economic organization, rapid construction, extensive trade relations - all this created the conditions for the flourishing of the glass industry in the possessions of Rome in the Mediterranean and in Western Europe. During the reign of Emperor Augustus, glass products were exported to France, Germany and Switzerland. It was the Romans who first began to use glass for architectural purposes - especially after the discovery of transparent glass by introducing manganese oxide into the glass mass, which happened around 100 BC. BC e. in Alexandria. Alexandria at that time was also a center for the production of glassware. The world-famous Portland vase (made of two-layer opaque glass) is perhaps the most famous masterpiece of the Alexandrian craftsmen.
In the Middle Ages, after the collapse of the Roman Empire, the movement of technology and the secrets of glassblowing skill slowed down, so eastern and western glassware gradually acquired more and more individual differences. Alexandria remained the center of glass production in the East, where elegant glassware was made.
By the end of the first millennium, the methods of glass production in Europe had changed significantly. First of all, this affected the composition of raw materials for production. Given the difficulties with the delivery of such a component of the mixture as soda, it was replaced with potash obtained as a result of burning wood. Therefore, glass made north of the Alps began to differ from glass made in Mediterranean countries such as Italy.
In the 11th century, German masters, and in the 13th century, Italian masters mastered the production of sheet glass. They first blew a hollow cylinder, then cut off its bottom, cut it and rolled it into a rectangular sheet. The quality of such a sheet was not high, but practically completely repeated the chemical composition of modern window panes. The windows of churches and castles of noble nobles were glazed with these glasses. The same period also saw the flourishing of stained-glass windows, in which pieces of colored glass were used.
At the end of the Middle Ages, Venice became the center of European glassmaking. In that historical period, the Venetian merchant fleet plowed the waters of the entire Mediterranean, which contributed to the rapid transfer of the latest technologies (especially from the East) to the fertile Venetian land. The manufacture of glass products was the most important craft in Venice, as evidenced by the number of glassblowers in this city - more than 8,000 people. In 1271, a special decree was issued that legitimized some protectionist measures to protect the interests of glassmaking, prohibited the import of foreign glass, the employment of foreign craftsmen and the export of raw materials for glass production abroad.
At the end of the 13th century, there were more than a thousand glass furnaces in Venice. However, frequent fires caused by their 24-hour operation forced the city authorities to move production to the nearby island of Murano.
This measure also gave some guarantees in the matter of maintaining the secrets of the production of Venetian glass, since the craftsmen did not have the right to leave the territory of the island.
In the second half of the 15th century, glassmakers on the island of Murano developed a new technology for making extra-clear glass, using quartz sand and potash made from seaweed. By the end of the 16th century, 3,000 of the island's 7,000 inhabitants were involved in the glass industry.
In the 17th century, the leadership in the development of glass production technology gradually passed to the English masters, in particular, thanks to the invention by George Ravencroft in 1674 of a new method for the production of crystal. He managed to get a better composition of glass than the Italian masters. Ravencroft replaced the potash with a high concentration of lead oxide and produced a highly reflective glass that lends itself very well to deep cutting and engraving.
France also did not stand aside from the development of glass production. In 1688, a new process for the production of mirror glass was established in Paris, the optical qualities of which until that time had left much to be desired. The molten glass mass was poured onto a special table and rolled out to a flat state. Then a multi-stage process of polishing the surface began, first with rough cast-iron discs, then with abrasive sand of various fractions, and finally with felt discs. The result was a mirror surface with unprecedented optical properties. High-quality mirrors were obtained from such glass, coated on the reverse side with a layer of silver. The French lured talented Venetian craftsmen with good professional skills and knowledge of the secrets of craftsmanship. The French authorities offered many incentives to the Venetian masters: for example, French citizenship after eight years of work and almost complete exemption from taxes.
But it was only at the end of the 19th century that glassmaking began to develop from handicraft into mass industrial production. One of the "fathers" of modern glass production can be called the German scientist Otto Schott (1851 - 1935), who actively used scientific methods to study the effect of various chemical elements on the optical and thermal properties of glass. In the field of studying the optical properties of glass, Schott teamed up with Ernst Ebbi (1840-1905), a professor from Jena and co-owner of the firm of Carl Zeiss. Another significant figure who contributed to the mass production of glass was Friedrich Simmens. He invented a new kiln that allowed much more glass to be continuously produced than before.
At the end of the 19th century, American engineer Michael Owens (1859–1923) invented the automatic bottle making machine. By 1920, there were approximately 200 Owens machines in operation in the United States. Soon, such machines became widespread in Europe. In 1905, the Belgian Furko made another revolution in the glass industry. He invented a method of vertically drawing a glass sheet of constant width from an oven. In 1914, his method was improved by another Belgian, Emile Bischeroy, who proposed stretching the glass sheet between two rollers, which greatly simplified the process of further glass processing.
In America, a similar process of drawing a glass sheet was developed somewhat later. Then the technology was improved with the support of the American firm "Libbey-Owens" and began to be used for commercial production in 1917. The float method was developed in 1959 by Pilkington. In this process, glass flows from the melting furnace in a horizontal plane in the form of a flat ribbon through a bath of molten tin for further cooling and annealing.
The advantages of this method in comparison with all the previous ones are stable glass thickness, high quality of the glass surface that does not require further polishing, the absence of optical defects in the glass, and high process productivity. The largest size of the resulting glass is usually 6 by 3.21 m, and the thickness of the sheet can be from 2 to 25 mm.
Currently, the world produces about 16,500 million tons of sheet glass per year. What does the glass making process look like today? Before an elegant mirror, a beautiful vase or light glass furniture appears from a set of chemical elements, these substances must go through a series of procedures. When creating glass or a mirror, first of all, substances with a low melting point are melted in huge baths that can hold up to a thousand tons of glass. Then quartz sand is added there, which successfully melts at a temperature of 1000 degrees. But this process cannot be considered complete: it is necessary to degas the resulting glass mass. To do this, it is heated in special regeneration furnaces to a temperature of 1400-1600 degrees. In the process of reaching the surface, the gases contribute to uniform mixing of the glass.
The glass production furnace operates continuously. On the one hand, ingredients are fed there, as a result of mixing which glass will be created. Gradually, they turn into molten glass mass and subsequently enter a special conveyor, on which the glass is cooled and cut into sheets of the desired size. In order to create not an ordinary glass, but a mirror, the craftsmen, in the process of moving the frozen glass along the conveyor, cover it first with a thin layer of silver, then with a layer of copper and, finally, varnish. In one minute of such processing, it is possible to create a mirror 2.5 meters long, and in a month such a furnace produces a mirror with an area of 40,000 square meters. m.
Imagine that you are returning from school, and there are no glasses in the windows of your apartment. Missing in the house and glassware. You want to look at your surprised face in the mirror, but he is not in the apartment either. Yes, and you would not have discovered many other useful things if glass had not been invented at one time. In this story, I will tell you how the history of glass began.
But what about the name of the inventor of glass? But no way. The fact is that it was created by nature itself. Long ago, many millions of years before the appearance of the first man, glass already existed. And it was formed from first red-hot, and then cooled lava, which escaped to the surface from volcanoes.
This natural glass is now called obsidian. But they could not glaze, for example, windows, not only because there were no windows then, but also because natural glass is dirty gray, through which absolutely nothing can be seen.
So how did glass fit for consumption come about? Maybe people have learned to wash it? Alas, natural glass is dirty not from the outside, but from the inside, so even the most modern detergents will not help here.
There are several legends about how people first made glass close to modern glass. They are all very similar and
they say that travelers, having no stones for the hearth at hand, used pieces of natural soda instead. Moreover, this happened in the desert or on the shore of a reservoir, where there was necessarily sand. And under the influence of fire, soda and sand melted, forming glass. People believed in these legends for a long time. But quite recently it turned out that all this is not true, because the heat from the fire is not enough for such an alloy.
People started making glass with their own hands more than 5000 years ago, in Egypt. True, even then it was not transparent, but due to the fact that foreign impurities came across in the sand, it had a green or blue tint. Gradually, the East learned to get rid of it. Judging by the excavations, the first glass items were beads. A little later, glass began to cover the dishes. And to learn how to make it yourself out of glass, it took another 2000 years.
In order to find out the secret of glass production, the government of Venice at the beginning of the 13th century sent special people to the east. By bribery and threats, the Venetians obtained this secret.
They set up their own production and were able to make the glass even more transparent, having guessed to add a little lead.
At first, glass was made in the Venice. The local authorities were very afraid that someone would find out the secret of production, so the area where these workshops were located was always cordoned off by soldiers. None of the workers dared to leave the city. For any attempt to do this, not only the glassmaker himself, but also his entire family was sentenced to death.
In the end, it was decided to move workshops on the island of Murano. It was more difficult to escape from there, and it was difficult to get there.
In 1271 Venetian grinders learned how to make lenses from glass, which at first were not in great demand. But in 1281 guessed to insert them into specially designed frames.
This is how the first glasses appeared. At first they cost so much that they were a wonderful gift even for kings and emperors.
At the end of the fifteenth century, when in Venice learned how to make dishes from glass, Murano products began to enjoy such popularity all over the world that additional ships had to be built to deliver them.
But the improvement of glass continued later. The time has come, and people came up with the idea of covering it with a special composition - an amalgam, so mirrors appeared.
In our country Glass production began a thousand years ago, in small workshops. And in 1634, the first glass factory was built near Moscow.