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  Quote +Protagorist Quote  Post ReplyReply #21 Posted: 22-Jan-2014 at 14:14

волја, креативност и слободоумност



јасно може да се импровизира и со мала [1] или електрична [2] иако секогаш може да се набави и на готово која и да е печка за стакло [1][2][3] а може и да се рента некоја услуга пр. во izo-staklo или во комшии кај konkav-konvex

за фузираното стакло може да се импровизира и со електрична печка за глина, доколку се внимава на температурата
Universal Heat
To properly make glass art using a pottery kiln, the firing process needs to be slowed down. A slower firing allows the kiln to achieve universal heating similar to a glass kiln.
Glass vs. Ceramic Kilns
The primary difference between a glass kiln and a ceramic kiln is that glass kilns heat from a single top layer, while ceramic kilns heat from multiple layers on the sides of the kiln. This is because most glass objects are relatively flat in comparison to ceramic objects; many glass objects must be heated evenly, with the entire face of the glass exposed to the same temperature at the same time to prevent cracking. Ceramic objects need more multi-level, multi-surface heating. http://www.ehow.com/about_6688483_glass-kilns-vs_-furnaces.html#ixzz2r8BChY1S








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  Quote +Protagorist Quote  Post ReplyReply #22 Posted: 02-Feb-2014 at 12:00
  

жед, конкуретност и трговија

јасно импровизации нема, освен ако не чоек има лихварско потекло пардон банкарско



Edited by +Protagorist - 10-Jun-2015 at 23:22
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  Quote +Protagorist Quote  Post ReplyReply #23 Posted: 17-Feb-2014 at 00:01

   



Edited by +Protagorist - 18-Feb-2014 at 14:31
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  Quote +Protagorist Quote  Post ReplyReply #24 Posted: 18-Feb-2014 at 14:25
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  Quote +Protagorist Quote  Post ReplyReply #25 Posted: 26-Feb-2014 at 14:52

(archived from the Borax Pioneer Magazine, 1994-2001)

Borax In Glass - Ancient Or Modern?

Just how long borax has been used by man is a question unlikely to be resolved. According to legend, Babylonians brought borax from the Far East more than 4,000 years ago to be used by goldsmiths, and writings have frequently cited ancient Egyptians as using it in metallurgy, medicine, and mummification, but none of this can be substantiated. The nitron baurak of the Greeks, the borith of the Hebrews, the baurack of the Arabians, the boreck of the Persians, and the burack of the Turks might all appear to express the same substance, borate of soda (i.e. borax). However, there is little evidence to show when or whether these names described the substance we now know as borax (Na2B4O7.10H2O). In fact, they are all transliterations of the Arabic word meaning to glitter or shine.

It seems probable that real borax was known to and used by craftsmen, scholars, and alchemists of the great Islamic civilization before 800 AD, and it is possible that Harun-al-Rashid's traders transported borate to China around that time; however if so, its origin is unknown. It wasn't until the Middle Ages that borax from Tibet was regularly imported into Europe. It was very expensive, and this limited it principally to the precious metal trade. Goldsmiths used it as a soldering agent and in the refining of metals and assaying of ores. The quantities traded were small, its method of production was secret, and its source remained a mystery until the second half of 18th century.

By the early 1500s, glass making was widely practiced in Europe, however there are no references to the use of borax. In trying to fix the first use of borax in glass, it needs to be remembered that prior to the 19th century, many accounts of glass were written by observers who were not themselves involved in the art. Technical secrets were passed on by word of mouth and practical instruction, and those who knew most were not given to writing for the benefit of others.

The earliest reference to borosilicate glass comes from China, where Zhao Rukuo described glassmaking by Arabs and others in 1225: "Borax is added so that the glass endures the most severe thermal extremes and will not crack". The earliest European mention of borax in glass occurs in a German work by Johann Kunckel in 1679, giving recipes for artificial gems.

In 1739, another German, Johann Cramer, recommended for crystal glass three parts of prepared flints (silica), one part of purest alkaline salt (potash), and one part burnt borace (borax). In 1758, Robert Dossie reported the best looking glass plates were ones containing 56 percent white sand, 23.5 percent pearl ashes (potash), 14 percent saltpeter, and 6.5 percent borax. He also notes that borax helps glass to receive certain colors.

Early use of borax in enamels and ceramics

The art of enameling began to take form in the early Byzantine era, but borax was not used in the frits applied to metals until the middle of the 18th century. The early borate-containing frits were colored ground glass used almost entirely for decorative purposes, and then in small quantities. The main increase in the use of borax did not come about until the enameling of iron created a new industry in the 19th century.

Enamel was first applied to sheet iron and steel in Austria and Germany about 1850. Cast-iron shapes such as cooking pots were pre-heated in furnaces. Frit was dusted on to the hot metal as a dry powder which sintered and stuck to the iron. The article was then returned to the furnace where the enamel melted to a smooth glaze. In this way, several coats of glass were normally added one by one to achieve the desired color and finish. The enamel frits had to be easily fusible, and borax became an important ingredient. By the end of the century, a worldwide trade had developed in all kinds of household goods, as well as durable advertisement displays, street names, and signs of all kinds, as enamel frit became the largest single use of borax.

Allied to enameling is the glazing and decoration of ceramics. The history of glazing, starting with the ancient Egyptian, Chinese, Babylonian, and Greek civilizations, is lengthy and complex. The earliest evidence of B2O3 use comes from China during the Liao dynasty (916 to 1125 AD). In recently discovered green shards, the glaze contains 13 percent boric oxide. The next examples come half a millennium later in the reign of Kangxi in China (1662 to 1722) and in Japan in 1699.

During the 18th century, potters and glassmakers in many parts of the world began to gain knowledge about the glazing properties of borax, but its price - £750 a ton in London in 1750 - remained far too high for general application. Then in the 19th century, technical developments in the ceramics industries coincided with new borate discoveries first in Italy, later in Turkey and the Americas which led to substantial reductions in price - less than £100 a ton in 1850, less than £20 by the 1890s. For the first time in history, borax became viable for modestly priced, mass-produced goods. Whereas Josiah Wedgwood's Etruria Works used no borax during his lifetime, less than a century later Staffordshire earthenware and soft porcelain glazes often contained between 12 and 25 percent borax.

For glazes and enamels, B2O3 is unique in that it acts simultaneously as a glass former, as a flux, and as a viscosity stabilizer that prevents the glaze from running too much while it is being fired. Perhaps most important of all, B2O3 reduces the thermal expansion of the glaze so that it can be matched to the expansion of the underlying ceramic or metallic body. At the same time, it improves aqueous and chemical durability while adding to the brilliance of the glaze.

Glass science - the borosilicate breakthrough

A scientific understanding of the way in which B2O3 could enhance the quality and performance of glass itself first began when Otto Schott persuaded Ernst Abbé from the University of Jena to join him and Karl Zeiss in forming the Jena Glassworks of Schott and Sons in Germany in 1884. Up to this time, there were only six elements commonly used in glass: silicon, oxygen, sodium, potassium, calcium, and lead. Schott and Abbé systematically investigated the introduction of a wide range of chemical elements into glass compositions. From this work they found that in the visible spectrum, glass containing B2O3 affected short wave length dispersion, so that it became a valuable constituent of optical glasses.

Schott and Abbé succeeded where others had failed in improving the optical properties of glass and at the same time increasing its resistance to water and chemical attack. They also discovered that glasses containing B2O3 could be formulated to withstand sudden changes in temperature. This led to the commercial manufacture of many products based on borosilicate glasses.

Beginning in the early 1900s, they invented a group of borosilicate glasses that were commercialized under the name of Jena Apparatus Glass. This was resistant to thermal shock and suitable for the chemical laboratory. By lowering the alkali content and increasing alumina, another group of glasses was developed which became known under the name Supremax of Schott and Genossen.

Low expansion borosilicate glass was first produced in the United States by Corning around the turn of the century for use by the railroad in signal lanterns. With the outbreak of war in 1914, supplies of laboratory glassware from Germany were no longer available, and Corning Glass Works became a new center for the production of borosilicate glasses. This led to a patent (by Sullivan and Taylor in 1915) for a low expansion borosilicate that was soon to revolutionize laboratory glassware and bring glass into the kitchen as cooking ware - Pyrex. With that the modern era of borosilicate glass technology can be said to have begun.

http://www.borax.com/library/articles/news-and-events/news-release/borax-in-glass---ancient-or-modern-

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  Quote +Protagorist Quote  Post ReplyReply #26 Posted: 09-Jul-2014 at 13:42

www.ilo.org/safework_bookshelf/english?content&nd=857171018

Glass

General profile
Glass was formed naturally from common elements in the earth’s crust long before anyone ever thought of experimenting with its composition, moulding its shape or putting it to the myriad of uses that it enjoys today. Obsidian, for instance, is a naturally occurring combination of oxides fused by intense volcanic heat and vitrified (made into a glass) by rapid air cooling. Its opaque, black colour comes from the relatively high amounts of iron oxide it contains. Its chemical durability and hardness compare favourably with many commercial glasses.

Glass technology has evolved for 6,000 years, and some modern principles date back to ancient times. The origin of the first synthetic glasses is lost in antiquity and legend.

Faience was made by the Egyptians, who molded figurines from sand (), the most popular glass-forming oxide. It was coated with natron, the residue left by the flooding Nile river, which was composed principally of calcium carbonate (), soda ash (), salt (NaCl) and copper oxide (CuO). Heating below 1,000 °C produced a glassy coating by the diffusion of the fluxes, CaO and into the sand and their subsequent solid-state reaction with the sand. The copper oxide gave the article an appealing blue colour.

According to the definition given by Morey: “Glass is an inorganic substance in a condition which is continuous with, and analogous to, the liquid state of that substance, but which, as the result of a reversible change in viscosity during cooling, has attained so high a degree of viscosity as to be, for all practical purposes, rigid.” ASTM defines glass as “an inorganic product of fusion that has cooled to a rigid condition without crystallizing.” Both organic and inorganic materials may form glasses if their structure is non-crystalline-that is, if they lack long-range order.

A most important development in glass technology was the use of a blow pipe (see figure 84.5), which was first used in approximately 100 years BC. From then onwards, there was a rapid development in the technique of manufacturing glass.



The first glass was coloured because of the presence of various impurities such as oxides of iron and chromium. Virtually colourless glass was first made some 1,500 years ago.

At that time glass manufacturing was developing in Rome, and from there it moved to many other countries in Europe. Many glass works were built in Venice, and an important development took place there. In the 13th century, many of the glass plants were moved from Venice to a nearby island, Murano. Murano is still a centre for the production of hand-made glass in Italy.

By the 16th century, glass was made all over Europe. Now Bohemian glass from the Czech Republic is well known for its beauty and glass plants in the United Kingdom and Ireland produce high-quality lead crystal glass tableware. Sweden is another country that is home to artistic glass crystalware production.

In North America the first manufacturing establishment of any sort was a glass factory. English settlers started to produce glass at the beginning of the 17th century at Jamestown, Virginia.

Today glass is manufactured in most countries all over the world. Many products of glass are made in fully automatic processing lines. Although glass is one of the oldest materials, its properties are unique and not yet fully understood.

The glass industry today is made up of several major market segments, which include the flat glass market, the consumer houseware market, the glass containers market, the optical glass industry and the scientific glassware market segment. The optical and scientific glass markets tend to be very ordered and are dominated by one or two suppliers in most countries. These markets are also much lower in volume than the consumer-based markets. Each of these markets has developed over the years by innovations in specific glass technology or manufacturing advancements. The container industry, for example, was driven by the development of high-speed bottle-making machines developed in the early 1900s. The flat glass industry was significantly advanced by the development of the float glass process in the early 1960s. Both of these segments are multi-billion-dollar businesses worldwide today.

Glass housewares fall into four general categories:

1. tableware (including dinnerware, cups and mugs)
2. drinkware
3. bakeware (or ovenware)
4. top-of-stove cookware.

While worldwide estimates are difficult to obtain, the market for glass housewares is undoubtedly on the order of US$1 billion in the United States alone. Depending upon the specific category, a variety of other materials compete for market share, including ceramics, metals and plastics.

Manufacturing processes
Glass is an inorganic product of fusion which has cooled to a rigid condition without crystallizing. Glass is typically hard and brittle and has a conchoidal fracture. Glass may be manufactured to be coloured, translucent or opaque by varying the dissolved amorphous or crystalline materials that are present.

When glass is cooled from the hot molten state, it gradually increases in viscosity without crystallization over a wide temperature range, until it assumes its characteristic hard, brittle form. Cooling is controlled to prevent crystallization, or high strain.

While any compound which has these physical properties is theoretically a glass, most commercial glasses fall into three main types and have a wide range of chemical compositions.

1. Soda-lime-silica glasses are the most important glasses in terms of quantity produced and variety of use, including almost all flat glass, containers, low-cost mass-produced domestic glassware and electric light bulbs.
2. Lead-potash-silica glasses contain a varying but often high proportion of lead oxide. Optical glass manufacture makes use of the high refractive index of this type of glass; hand-blown domestic and decorative glassware makes use of its ease of cutting and polishing; electrical and electronic applications takes advantage of its high electrical resistivity and radiation protection.
3. Borosilicate glasses have a low thermal expansion and are resistant to thermal shock, which makes them ideal for domestic oven and laboratory glassware and for glass fibre for plastic reinforcements.

A commercial glass batch consists of a mixture of several ingredients. However, the largest fraction of the batch is made up of from 4 to 6 ingredients, chosen from such materials as sand, limestone, dolomite, soda ash, borax, boric acid, feldspathic materials, lead and barium compounds. The remainder of the batch consists of several additional ingredients, chosen from a group of some 15 to 20 materials commonly referred to as minor ingredients. These latter additions are added with a view to providing some specific function or quality, such as colour, which is to be realized during the glass preparation process.

Figure 84.6 illustrates the basic principles of glass manufacture. The raw materials are weighed, mixed and, after the addition of broken glass (cullet), taken to the furnace for melting. Small pots of up to 2 tonnes capacity are still used for the melting of glass for hand-blown crystalware and special glasses required in small quantity. Several pots are heated together in a combustion chamber.

Figure 84.6.    The processes and materials involved in the manufacture of glass



In most modern manufacture, melting takes place in large regenerative, recuperative or electric furnaces built of refractory material and heated by oil, natural gas or electricity. Electric boosting and cold top electric melting were commercialized and became extensively utilized globally in the late 1960s and 1970s. The driving force behind cold top electric melting was emission control, while electric boosting was generally used in order to improve glass quality and to increase throughput.

The most significant economic factors concerning the use of electricity for glass furnace melting are related to fossil fuel costs, the availability of various fuels, electricity costs, capital costs for equipment and so on. However, in many instances the prime reason for the use of electric melting or boosting is environmental control. Various locations worldwide either already have or are expected soon to have environmental regulations that strictly restrict the discharge of various oxides or particulate matter in general. Thus, manufacturers in many locations face the possibility of either having to reduce glass melting throughputs, install baghouses or precipitators in order to handle waste flue gases or modify the melting process and include electric melting or boost. The alternatives to such modification may in some cases be plant shutdowns.

The hottest part of the furnace (superstructure) may be at 1,600 to 2,800°C. Controlled cooling reduces the glass temperature to 1,000 to 1,200°C at the point where the glass leaves the furnace. In addition, all types of glass are subjected to further controlled cooling (annealing) in a special oven or lehr. Subsequent processing will depend on the type of manufacturing process.

Automatic blowing is used on machines for bottle and lamp bulb production in addition to traditional hand-blown glass. Simple shapes, such as in insulators, glass bricks, lens blanks and so on, are pressed rather than blown. Some manufacturing processes use a combination of mechanical blowing and pressing. Wired and figured glass is rolled. Sheet glass is drawn from the furnace by a vertical process which gives it a fire-finished surface. Owing to the combined effects of drawing and gravity, some minor distortion is inevitable.

Plate glass passes through water-cooled rollers onto an annealing lehr. It is free from distortion. Surface damage can be removed by grinding and polishing after fabrication. This process has largely been replaced by the float glass process, which was introduced in recent years (see figure 84.7). The float process has made possible the manufacture of a glass that combines the advantages of both sheet and plate. Float glass has a fire-finished surface and is free from distortion.

Figure 84.7. Continuous float process



In the float process, a continuous ribbon of glass moves out of a melting furnace and floats along the surface of a bath of molten tin. The glass conforms to the perfect surface of the molten tin. On its passage over the tin, the temperature is reduced until the glass is sufficiently hard to be fed onto the rollers of the annealing lehr without marking its under surface. An inert atmosphere in the bath prevents oxidation of the tin. The glass, after annealing, requires no further treatment and can be further processed by automatic cutting and packing (see figure 84.8).

Figure 84.8.      Ribbon of float glass exiting from lehr after being annealed



Libbey-Owens-Ford
______________________________________________________________________


The trend in new residential and commercial architecture toward the inclusion of more glazing area, and the need to reduce energy consumption, has put increased emphasis on improving the energy efficiency of windows. Thin films deposited at the surface of the glass provide low emissivity or solar control properties. The commercialization of such commodity-coated products requires a low cost, large area deposition technology. As a result, an increasing number of float glass manufacturing lines are equipped with sophisticated on-line coating processes.

In commonly used chemical vapour deposition (CVD) processes, a complex gas mixture is brought into contact with the hot substrate, where it pyrolytically reacts to form a coating at the surface of the glass. In general, the coating equipment consists of thermally controlled structures which are suspended over the width of the glass ribbon. They may be located in the tin bath, the lehr gap or the lehr. The function of the coaters is to uniformly deliver the precursor gases over the ribbon width in a temperature-controlled fashion and to safely extract the exhaust gas by-products from the deposition region. For multiple coating stacks, multiple coaters are used in series along the glass ribbon.

For the treatment of the exhaust gas by-products generated by such large-scale processes, wet scrubbing techniques with a conventional filter press are normally sufficient. When the effluent gases are not easily reacted or wetted by aqueous solutions, incineration is the primary option.

Some optical glasses are chemically strengthened by processes which involve immersing the glass for several hours in high-temperature baths containing molten salts of, typically, lithium nitrate and potassium nitrate.

Safety glass is of two major types:

1. Toughened glass is made by pre-stressing by heating and then rapidly cooling pieces of flat glass of desired shape and size in special ovens.
2. Laminated glass is formed by bonding a sheet of plastic (usually polyvinyl butyral) between two thin sheets of flat glass.

Synthetic Vitreous Fibres

General profile
Synthetic vitreous fibres are produced from a wide variety of materials. They are amorphous silicates manufactured from glass, rock, slag or other minerals. The fibres produced are both continuous and discontinuous fibres. In general, the continuous fibres are glass fibres drawn through nozzles and used to reinforce other materials, such as plastics, to produce composite materials with unique properties. The discontinuous fibres (generally known as wools) are used for many purposes, most commonly for thermal and acoustical insulation. Synthetic vitreous fibres, for purposes of this discussion, have been divided into continuous glass fibres, with the insulation wools made of glass, rock or slag fibres, and refractory ceramic fibres, which are generally aluminium silicates.

The possibility of drawing heat-softened glass into fine fibres was known to glass makers in antiquity and is actually older than the technique of glass blowing. Many early Egyptian vessels were made by winding coarse glass fibres onto a suitably shaped mandrel of clay, then heating the assembly until the glass fibres flowed into one another and, after cooling, removing the clay core. Even after the advent of glass blowing in the 1st century AD, the glass fibre technique was still employed. Venetian glassmakers in the 16th and 17th centuries used it for decorating glassware. In this case, bundles of opaque white fibres were wound onto the surface of a plain transparent blown glass vessel (e.g., a goblet) and then fused into it by heating.

Despite the long history of generally decorative or artistic uses of glass fibres, widespread use did not arise again until the 20th century. Initial commercial US production of glass fibres occurred in the 1930s, while in Europe the initial use occurred some years earlier. Rock and slag wools were produced several years earlier than that.

The manufacture and use of synthetic vitreous fibres is a global multi-billion-dollar industry since these useful materials have become an important component of modern society. Their uses as insulations have resulted in tremendous reduction in energy requirements for heating and cooling buildings, and this energy savings has resulted in significant reduction in global pollution associated with energy production. The number of applications of continuous glass filaments as reinforcements for a plethora of products, from sporting goods to computer chips to aerospace applications, has been estimated to be in excess of 30,000. The development and widespread commercialization of refractory ceramic fibres occurred in the 1970s, and these fibres continue to play an important role in protecting workers and equipment in a variety of high-temperature manufacturing processes.

Manufacturing processes

Continuous glass filaments
Glass filaments are formed by drawing the molten glass through precious-metal bushings into fine filaments of nearly uniform diameter. Due to the physical requirements for the fibres when used as reinforcements, their diameters are relatively large compared to those in the insulation wools. Almost all continuous glass filaments have diameters of 5 to 15 mm or greater. These large diameters, coupled with the narrow range of diameters produced during the manufacture, eliminate any potential chronic respiratory effects, as the fibres are too large to be inhaled into the lower respiratory tract.

Continuous glass fibres are made by the rapid attenuation of drops of molten glass exuding through nozzles under gravity and suspended from them. The dynamic balance between the forces of surface tension and mechanical attenuation results in the drop of glass taking on the shape of a meniscus held at the annular opening of the nozzle and tapering to the diameter of the fibre being drawn. For fibre drawing to be successful, the glass has to be within a narrow range of viscosities (i.e., between 500 and 1,000 poise). At lower viscosities, the glass is too fluid and falls away from the nozzles as drops; in this case surface tension dominates. At higher viscosities, the tension in the fibre during attenuation is too high. The rate of flow of glass through the nozzle can also become too low to maintain a meniscus.

The function of the bushing is to provide a plate containing several hundred nozzles at a uniform temperature and to condition the glass to this uniform temperature so that the fibres drawn are of uniform diameter. Figure 84.9 shows a schematic diagram of the principal features of a direct-melt bushing attached to a forehearth from which it takes a supply of molten glass very near the temperature at which the glass will pass through the nozzles; in this case, therefore, the basic function of the bushing is also its sole function.

______________________________________________________________________

Figure 84.9.     Schematic of direct-melt bushing



In the case of a bushing operating from marbles, a second function is required-namely, to first melt the marbles before conditioning the glass to the correct fibre-drawing temperature. A typical marble bushing is shown in figure 84.10. The broken line within the bushing is a perforated plate which retains the unmelted marbles.

______________________________________________________________________

Figure 84.10. Schematic of a marble bushing



The design of bushings is largely empirical. For reasons of resistance to attack by molten glass and stability at the temperatures needed for fibre drawing, bushings are made from platinum alloys; both 10% rhodium-platinum and 20% rhodium-platinum are used, the latter being more resistant to distortion at elevated temperatures.

Before the individual fibres being drawn from a bushing are gathered and consolidated into a strand, or a multiplicity of strands, they are coated with a fibre size. These fibre sizes are basically of two types:

1. starch-oil sizes usually applied to fibres intended for weaving into fine fabrics or similar operations
2. keying agent plus film-former sizes applied to fibres intended for the direct reinforcement of plastics and rubber.

After the fibre is formed, a protective coating of organic sizing is applied at an applicator and the continuous filaments are gathered into a multifilament strand (see figure 84.11) before being wrapped on a winding tube. Applicators function by allowing the fan of fibres, when about 25 to 45 mm wide and on their way to the gathering shoe below the applicator, to pass over a moving surface covered with a film of fibre size.

______________________________________________________________________

Figure 84.11.     Textile glass filaments being pulled through bushing. Filaments are gathered into strands and wound into packages for processing



Owens Corning
______________________________________________________________________


There are basically two types of applications:

1. roller applicators, made of rubber, ceramic or graphite, in which the fibre runs over the surface of the roller coated with a film of fibre size
2. belt applicators, in which at one end the belt passes over a driven roller which dips the belt into the fibre size and at the other end passes over a fixed hard chrome steel bar at which position the fibres touch the belt to pick up the size.

The protective coating and the fibre-gathering process can vary depending on the types of textile or reinforcement fibre being produced. The basic objective is to coat the fibres with size, gather them into a strand and locate them on a removable tube on the collet with the minimum necessary tension.

Figure 84.12 shows the process of continuous glass manufacturing.

______________________________________________________________________

Figure 84.12.     Continuous filament glass manufacturing



Insulation wool manufacturing
In contrast to continuous filaments, the fibres of the insulation wools and refractory ceramic fibres are made in very high energy processes in which molten material is dropped into either spinning discs or a series of rotating wheels. These methods result in the production of fibres with a range of diameters much wider than seen with continuous filaments. Thus, all of the insulation wools and ceramic fibres contain a fraction of the fibres with diameters of less than 3.0 mm; these could become respirable if fractured into relatively short lengths (less than 200 to 250 mm). Extensive data are available on exposures to respirable synthetic vitreous fibres in the workplace.

Several processes are used to manufacture glass wool, including the steam blowing process and flame blown process; but the most popular is the rotary forming process developed in the mid-1950s. The rotary processes have largely replaced direct blowing processes for the commercial production of glass-fibre insulation products. These rotary processes all employ a hollow drum, or spinner, mounted with its axis vertical. The vertical wall of the spinner is perforated with several thousand holes uniformly distributed around the circumference. Molten glass is allowed to fall at a controlled rate into the centre of the spinner, from where some suitable distributor forces it to the inside of the vertical perforated wall. From that position, centrifugal force drives the glass radially outwards in the form of discrete glass filaments issuing from every perforation. Further attenuation of these primary filaments is achieved by a suitable blowing fluid emerging from a nozzle or nozzles arranged around and concentric with the spinner. The net result is the production of fibres with a mean fibre diameter of 6 to 7 mm. The blowing fluid acts in a downwards direction and so, as well as providing the final attenuation, it also deflects the fibres towards a collecting surface situated below the spinner. On the way to this collecting surface, the fibres are sprayed with a suitable binder before being uniformly distributed across the collecting surface (see figure 84.13).

______________________________________________________________________

Figure 84.13.     The rotary process for making glass wool fibres



In a rotary process, glass wool fibres are made by allowing molten glass to run through a series of small openings which are situated in a revolving spinner and then attenuating the primary filament by air or steam blowing.

Mineral wool, however, cannot be produced on the rotary spinner process and historically has been produced in process with a series of horizontal spinning mandrels. The mineral wool process consists of a set of rotors (mandrels) mounted in a cascade formation and rotating very rapidly (see figure 84.14). A stream of molten stone is continuously transferred to one of the upper rotors and from this rotor distributed on the second and so on. The melt is uniformly spread on the outside surface of all the rotors. From the rotors, droplets are thrown out by centrifugal force. The droplets are attached to the rotor surface by elongated necks which, under further elongation and simultaneous cooling, develop into fibres. The elongation is, of course, followed by a decrease in diameter which, in turn, causes an accelerated cooling. Thus, there is a lower limit for the diameter among fibres produced in this process. A normal distribution of fibre diameters around the mean value is, therefore, not expected.

______________________________________________________________________

Figure 84.14.     Mineral wool process (rock and slag)





Edited by +Protagorist - 10-Jul-2014 at 08:07
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  Quote +Protagorist Quote  Post ReplyReply #27 Posted: 23-Jul-2014 at 09:18

Quartz glass is one of the most extraordinary materials used in industry and research. Due to the combination of a number of very specific properties not given by any other material, quartz glass has cleared the way for many high-tech applications. Examples are the fabrication of computer processors and chips, modern laser technology or water treatment with UV lamps. Three aspects are crucial for most applications: purity, light and heat.
A number of unique optical, mechanical and thermal properties have made quartz glass an indispensable material in the fabrication of high-tech products. Among these are:
  • high chemical purity and resistance,

  • high softening temperature and thermal resistance,

  • low thermal expansion with high resistance to thermal shocks,

  • high transparency from the violet to the infrared spectral range,

  • high irradiation resistance.
    Long-time experience and constant development have given Heraeus Quarzglas the competence to manufacture this extraordinary material in well-established and innovative production processes and to tailor its properties to the intended application.

       
    Introduction to quartz glass

    The introduction lists the physical and chemical properties of “ordinary“ glass and quartz glass as the purest form of glass respectively. In the first part, the properties of “ordinary” glass will be elucidated. The historical background of glass as one of the oldest materials forms the basics with the connection to quartz glass and a short overview on its unique material properties. The exceptional position of quartz glass as high end product for the microchip industry will be introduced.

    General about SiO2:
    The following paragraph describes the correlation between:
    Silicon Dioxide – Glass – Quartz – Fused Silica.

    Silicon Dioxide (SiO2) is the simple chemical composition of glass. Quartz is the most stable crystal modification at normal temperature and pressure conditions. The mineral is a widely spread mineral in the earths crust. Glass (from “glasa”, Germanic for amber, the shiny or shimmery) also consists of silicon and oxide, but is a uniform amorphous solid material. Many glass varieties are clear and transparent respectively. This means transmissibility for the visible spectrum of light. In general such glasses are associated with glass. Transparent materials allow light to pass through them without diffusing (scattering) the light.

    Most common types of glass:
    At least 2000 years ago we learned how to lower the softening temperatures by adding lime an soda before heating, which resulted in a glass containing sodium and calcium oxide. Glass – Additives and the industrial use of glass The use of glass as one of the oldest, but also very important materials for the industry is linked with the application of additives. Chemical like soda (Sodium carbonate, Na2CO3) and in the past also potash (potassium carbonate, K2CO3), manganese oxide and metal oxides influence the properties of glass. Manufactured glass is a material formed when a mixture of sand, soda and lime is heated to a high temperature and stays in a molten, liquid state. Glass can be made from pure silica, but quartz glass (also referred as quartz) has a high glass transition point at around 1200°C, which makes it difficult to mound into panes or bottles.

    Quartz glass is the purest form of SiO2 and therefore the most valuable and sophisticated variety. Extremely clear glass can be used for optical fibers. Therefore synthetic quartz glass is used to transmit light across many kilometers. Lots of glasses are impermeable for ultraviolet radiation, but only pure fused silica (only SiO2) is permeable for wavelengths
    < 350 nm (UV). Quartz glass also exists as an opaque variety and with different coloration to change the physical and chemical properties like transmission or absorption for specific wavelength (filter glass). The opaque material at Heraeus, OM 100, is also used as a heat barrier or for diffuse scattering of IR radiation.

    http://heraeus-quarzglas.com/en/quarzglas/introduction/Introduction.aspx
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      Quote +Protagorist Quote  Post ReplyReply #28 Posted: 13-Aug-2014 at 18:41



    World's thinnest glass shatters records -- by accident

    At just one molecule thick, researchers at Cornell and Germany's University of Ulm have discovered the world's thinnest sheet of glass -- by accident.

    The “pane” of glass, so impossibly thin that its individual silicon and oxygen atoms are clearly visible via electron microscopy, was identified in the lab of David A. Muller, professor of applied and engineering physics and director of the Kavli Institute at Cornell for Nanoscale Science.

    The work that describes direct imaging of this thin glass was published in January 2012 in Nano Letters, and the Guinness records officials took note. They published the achievement in early September for inclusion in the 2014 book, and the breakthrough is featured in the publication’s 21st Century Science spread.

    Just two atoms in thickness, making it literally two-dimensional, the glass was an accidental discovery, Muller said. The scientists had been making graphene, a two-dimensional sheet of carbon atoms in a chicken wire crystal formation, on copper foils in a quartz furnace. They noticed some “muck” on the graphene, and upon further inspection, found it to be composed of the elements of everyday glass – silicon and oxygen.

    They concluded that an air leak had caused the copper to react with the quartz, also made of silicon and oxygen. This produced the glass layer on the would-be pure graphene.

    Besides its sheer novelty, Muller continued, the work answers an 80-year-old question about the fundamental structure of glass. Scientists, with no way to directly see it, had struggled to understand it: It behaves like a solid but was thought to look more like a liquid.

    Now, the Cornell scientists have produced a picture of individual atoms of glass, and they found it strikingly resembles a diagram drawn in 1932 by W.H. Zachariasen – a longstanding theoretical representation of the arrangement of atoms in glass.

    “This is the work that, when I look back at my career, I will be most proud of,” Muller said. “It’s the first time that anyone has been able to see the arrangement of atoms in a glass.”

    What’s more, two-dimensional glass could someday find a use in transistors, by providing a defect-free, ultra-thin material that could improve, for example, the performance of processors in computers and smartphones.

    The paper, “Direct Imaging of a Two-Dimensional Silica Glass on Graphene,” was published in Nano Letters on Jan. 23, 2012, with first authors Pinshane Huang, a Cornell graduate student, and Simon Kurash, a University of Ulm graduate student. It includes collaborators from the University of Ulm, Germany; the Max Planck institute for Solid State Research in Germany; University of Vienna; University of Helsinki; and Aalto University in Finland.

    The work at Cornell was funded by the National Science Foundation through the Cornell Center for Materials Research.

    http://www.news.cornell.edu/stories/2013/09/shattering-records-thinnest-glass-guinness-book


    ...
    The snippet of video shows atoms rearranging in the glass, with different atomic behaviors in four different regions of the material. “Everyone thought it was impossible to see atoms moving in a glass, and suddenly we were able to do it with this new, ultrathin glass,” Huang says.
    ...
    http://ceramics.org/ceramic-tech-today/video-dancing-atoms-in-worlds-thinnest-glass

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      Quote +Protagorist Quote  Post ReplyReply #29 Posted: 30-Oct-2014 at 21:12
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      Quote +Protagorist Quote  Post ReplyReply #30 Posted: 31-Oct-2014 at 17:55

    веројатно за cut-out комбинации неопходно е ласерски цо2 катер [1] ко кинескиов иако кај ефтините ето велат не се знае што ќе стигне, евентуално ако микросам имаат нешто конкуретно на лагер

    инаку освен сечење истиот е иделен и за гравирање иако ручни рад му е мајката за уникати со душа
    Originally posted by +Protagorist

    ова резбаново стакло е фина уметност иако полуавтоматски се резба [1][2][3][4] зато поќеиф ми прават рачни стаклени резбарии [5]


    но и ова не ет за потценување

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      Quote +Protagorist Quote  Post ReplyReply #31 Posted: 02-Nov-2014 at 14:38

    Originally posted by pbanks

    имам еден бениген проблем. Ме вади од кожа огледалото што се замаглува, неможам да се избричам како човек. Мислев дека отворен прозорец ќе биде доволно но ништо од тоа. Не сакам да го бушам ѕидот и да вградувам вентилатор. Едно од решенијата се влошки со греачи кои се поставуваат позади огледалкото и работат на струја. Ефектот е како жиците на задното стакло во колата. Такви греачи кај нас ниту во комшилук нема ни за лек, луѓе ме гледаат бело кога прашувам. Офтопик овдека, но...


    да не кршам клечки пошто и јас не би купил ова анти-фог фолијава, ама доколку ти збоктисало од то пареата, а ето не ти се става вентилација, види набави ваква фолија http://www.fsicti.com/index.php?pid=34&lid=1

    имаш и кинески на алибаба, а кои можеби се и поисплатливи за diy комбинации, но и fsi фолијава сигурно ќе ја биде доколку ја дадеш профи стаклар да ја залепи
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      Quote Max Quote  Post ReplyReply #32 Posted: 24-Nov-2014 at 22:33
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      Quote Max Quote  Post ReplyReply #33 Posted: 09-May-2015 at 10:52



    Matiranje Stakla - Sam Svoj Majstor - 9/1987 

    Ramadan Mujacic iz Brckog pita kako se staklo matira sa fluorovodicnom kiselinom i da li je kiselina stetna za zdravlje i gdje se moze nabaviti

    Fluorovodicna kiselina se ne prodaje u trgovackoj mrezi, vec je morate nabaviti direktno od proizvodjaca. Njome treba posebno oprezno postupati, jer osim sto je izuzetno agresivna - isparavanja su vrlo stetna po zdravlje pa treba raditi pri dobroj ventilaciji ili na otvorenom prostoru.

    Obavezno morate imati zastitne rukavice, masku i naocale, a preporucujemo vi i staru odjecu. Fluorovodicnu kiselinu za nagrianje stakla treba razrijediti s oko 20 posto vode. Napominjemo da se ovom tehnologijom ne postize tako dobar efekt matiranja kao s peskarenjem, pa je ovaj nacin nagrianja stakla povoljniji pri izradu natpisa reklama i ornamenata na staklu, negoli kod matiranja.

    http://en.wikipedia.org/wiki/Glass_etching [1][2]

    ~

    сепак денес ласер или повпечатливо пескарење се норма  


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      Quote Max Quote  Post ReplyReply #34 Posted: 10-Jun-2015 at 23:05


    самото стакло како појава е убаво само по себе, слично ко човечка душа чии особини можат да се оплеменат, надополнат или истетовираат, но можат и да се избистрат доколку наново се препечат, битно да внимава човек како ги куландрисва бидејки некои парчиња двапати неможат да се имаат в рака, иако и скршени муабети можат да се лепат, но истите потем најчесто служат за украс 

    [1] http://www.tokecity.com/forums/

    блазе си им на оние кои се сами свои мајстори иако и ним им требало учител некогаш, та ксметлии се оние ко сакаат и имаат каде да научат, само што денес нели за занает, уметност или хоби време не се наоѓа, чинам се помалку и виртуелно

    http://www.warm-glass.co.uk/online-education-cms-62.html





    Edited by Max - 28-Sep-2015 at 14:25
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      Quote Max Quote  Post ReplyReply #35 Posted: 11-Jun-2015 at 12:07
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      Quote Max Quote  Post ReplyReply #36 Posted: 11-Jun-2015 at 15:51


    http://en.wikipedia.org/wiki/Tessera#Historical_tessera

    http://www.sussex.ac.uk/byzantine/mosaic/browse/structures

    http://www.inlandcraft.com/howto/mosaic/mosaic1.htm [1

    [1] песок место хартија и лепак ко фиксер е далеку полесен начин за аранжирање иако помалку прецизен

     


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      Quote Max Quote  Post ReplyReply #37 Posted: 24-Jun-2015 at 18:28


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      Quote Max Quote  Post ReplyReply #38 Posted: 07-Jul-2015 at 00:18

    едноставноста навистина плени

    http://www.blueskiesglassworks.com/glass_home.htm

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      Quote nenad Quote  Post ReplyReply #39 Posted: 10-Jul-2015 at 09:38
    Прозорско стакло - иако иѕгледа дека сите стакла се исти постојат многу разлики, а и науката длабоко се инволвира во производство на квалитетно стакло кое има зголемени изолациони и физички својства.


    карактеристики на модерно проѕорско стакло



    гларија на рани видови стакло
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      Quote mukial Quote  Post ReplyReply #40 Posted: 27-Jul-2015 at 08:11
    Dear all.
    Good day!

    we produce the PDLC film for smart switchable glass, it is laminated by EVA film at 80 degree.
    This kind of glass can turn opaque to transparent through controlling the power supply( also you can control it by remote.

    The transparency is up 80% when turns on, and maximum size is 1800*3000meter.




    EVA film for laminated glass and smart switchable glass manufacturer based in China.
    contact: mukial@huichiglass.com
    website:www.decorglasss.com
    skype: mukial zhang
    whatsapp:+8618922173106
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