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Glass

GlassIs an amorphous solid material which is often transparent and has widespread practical, technological, and decorative usage in things like window panes, tableware, and optoelectronics.2History of GlassPeople had used naturally occurring glass, especially obsidian (the volcanic glass) before they learned how to make glass.The ancient Roman historian Pliny suggested that Phoenician merchants had madethe first glass in the region of Syria around 5000BC.But according to the archaeological evidence, the first man made glass was in Eastern Mesopotamia and Egypt around 3500BC and the first glass vessels were made about 1500BC in Egypt and Mesopotamia. For the next 300 years, the glass industry was increased rapidly and then declined.

The ancient Roman historian Pliny suggested that Phoenician merchants had madethe first glassin the region of Syria around 5000BC. But according to the archaeological evidence, the first man made glass was in Eastern Mesopotamia and Egypt around 3500BC and the first glass vessels were made about 1500BC in Egypt and Mesopotamia. For the next 300 years, the glass industry was increased rapidly and then declined. In Mesopotamia it was revived in the 700BC and in Egypt in the 500s BC. For the next 500 years, Egypt, Syria and the other countries along the eastern coast of the Mediterranean Sea were centers forglass manufacturing.In the beginning it was very hard and slow to manufacture glass.Glass melting furnaceswere small and the heat they produced was hardly enough to melt glass. But in the 1st century BC, Syrian craftsmen invented the blow pipe. This revolutionary discovery made glass production easier, faster and cheaper. Glass production flourished in the Roman Empire and spread from Italy to all countries under its rule. In 1000 AD the Egyptian city of Alexandria was the most important center of glass manufacture. Throughout Europe the miraculous art of making stained glass on churches and cathedrals across the continent reached its height in the finest Chatres and Conterburycathedral windowsproduced in the 13th and 14th centuries.3

Glassblowingis a glassforming technique that involves inflating moltenglassinto a bubble (or parison), with the aid of ablowpipeGlassblower Romeo Lefebvre in his workshop inMontreal, 19424Materials

A particular sand deposit that contains almost nothing but silicate minerals.The most common sand forming mineral is quartz.Other components of silica sand: cristobalite, tridymite, aluminum, feldspar The primary ingredient for glass productionAlso called as INDUSTRIAL SANDSilica sand deposits are most commonly surfacemined in open pit operations, but dredging and underground mining are also employedSilica Sand

Country House Silica Sand Quarry

Sodium Carbonate (Na2CO3)also known as washing soda, soda ash and soda crystalsmain use in glass making is that it acts as a flux for silicaThere are two main sources of sodium carbonate:a) from salt and calcium carbonate (via the ammonia soda (Solvay) process)b) from sodium carbonate and hydrogen carbonate ores (trona and nahcolite)acts as a flux for silica- lowers the melting point of the mixture

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THE SOLVAY PROCESS

trona(Na2CO3.NaHCO3.2H2O) nahcolite (NaHCO3)

Limea manmade chemical which is produced from a sufficiently pure sedimentary rock by heating it to high temperature in a kiln. This process is referred to as"calcining"the limestone.The word "lime" originates with its earliest use as building mortar and has the sense of "sticking or adhering.Addition of lime increases the hardness and chemical durability and insolubility of glassMAGNESIUM OXIDE AND ALUMINIUM OXIDE can also be used to enhance the properties of glass.2 Types of Lime:a. Quicklimeb. Hydrated Lime

Calcining=A chemical decomposition of limestone into the oxide and carbon dioxide11

THE LIME CYCLEAfter processing, products derived from limestone have the unique ability to return to their original chemical form. The lime cycle consists of first burning of limestone to form quicklime. Hydrated lime can then be produced by adding water to the quicklime. At this point, carbon dioxide in the atmosphere or from industrial processes react with hydrated lime to convert it back to limestone. This cycle is called the lime cycle. The time it takes for quicklime or hydrated lime to be converted back to limestone can span from less than an hour with the aid of certain industrial processes to several years if left at atmospheric conditions.

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Limestone Quarry in New ZealandAdditives:

1. Lead Oxidehas better reflective properties and therefore the glass seems to sparkle.

"oxide" is a chemistry term used when oxygen is attached to another element,formingan ionic or covalent bond.14Additives: 2.Boric Oxide-Pure form of B2O3-changes the thermal and electrical properties of the glass

used to make Pyrex glassware which can withstand extremes of heat and cold.

Pure B2O3is needed for the production of certain types of glasses including optical and telescope lenses, medical glasses (ampoules), electronic glasses and glass-ceramic composites. The general benefits of using B2O3in glass formulations are reduction of melting temperature, increased thermal resistance and mechanical strength, and enhanced aqueous and chemical durability.15Additives: 3.Potassium Oxide-mostly used to make stained glass windows for medieval cathedrals.

16Additives: 4.Zinc Oxide-excellent raw material for manufacturing optical glass-also used for UV-blocking sunglasses

17Additives: 5. Barium Oxide-replaced lead (II) oxide in the production of certain kinds of glass such as optical crown glass.

18Additives: 6. Germanium Oxide- added to glass to increase the index of refraction

19Requirements to Produce GlassThe quality of the glass depends largely on the quality of the sand. For example only the purest sand can be used for the production of optical glass.Clay materials are objectionable.Melting process should be permanently controlled.Pass the thermal shock testing, rain testing and strain testing (depends on type of glass).slight impurities, especially small quantities of iron, tend to destroy these effects. The sand should be nearly white in color; it should be of medium fineness (passing a 20 to 50 mesh horizontal sieve); the grains should be uniform in size, even, and angular, or, less preferably, they may be rounded.Cloud the glas. A simple chemical test may be employed by heating the sand in a dilute acid. Effervescence indicates the presence of lime; loss of color shows the presence of clay impurities.s3. 21Types of Glass(according to intended application )

Annealed Glassthe basic flat glass product that is the first result of the float process. It is common glass that tends to break into large, jagged shards. It is used in some end products and often in double-glazed windows.

Annealingis a process of slowly cooling hotglassto relieve internal stresses after it was formed. The process may be carried out in a temperature-controlledkilnknown as alehr.

The glass is heated until thetemperaturereaches astress-relief point, that is, theannealing temperature(also calledannealing point) at aviscosity, at which the glass is still too hard todeform, but is soft enough for the stresses to relax. The piece is then allowed to heat-soak until its temperature is even throughout23

Toughened Glassfar more resistant to breakage than simple annealed glass and designed to break in a more predictable way when it does break, thus providing a major safety advantage in almost all of its applications.

Laminated GlassRegarded as safety glass.manufactured by combining two or more annealed or heat treated glass sheets bonded with one or more of PVB (polyvinyl butyral) interlayers and subjected to heat and pressure, in order to ensure perfect adhesion between the constituent elements.

Coated GlassSurface coatings are applied to glass to modify its appearance and give it many of the advanced characteristics and functions such as low maintenance, special reflection/transmission/absorption properties, scratch resistance, corrosion resistance, etc.

Mirrored Glassa metal coating is applied to one side of the glass. The coating is generally made of silver, aluminium, gold or chrome. For simple mirrored glass, a fully reflective metal coating is applied and then sealed with a protective layer. To produce "one-way" mirrors, a much thinner metal coating is used, with no additional sealing or otherwise opaque layer.

Patterned Glassflat glass whose surfaces display a regular pattern.mostly used in internal decoration and internal architecture. It is typically used for functional reasons, where light but not transparency is desired.

Extra Clear Glassmade with a very low iron content in order to minimize its sun reflection propertieslets as much light as possible through the glass.

Moldavite, a natural glass formed bymeteorimpact, fromBesednice, Bohemia29