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What would our life be without Glass?
     

Glass is an inorganic material, usually transparent or translucent, which is hard, brittle and impervious to the natural elements and which is a poor conductor of heat and electricity.
People like glass especially for it's luminous transmittance and because it is hard, inert, impervious and because it is a poor heat conductor. It's therefore the ideal material for windows, food containers and drinkware.

A property of glass: Breakable
A property of glass: breakable



The 'invention' of glass

Glass is an amazing material. The luminous transmittance must have been a miracle for the person who first, long long ago, saw this material.
 
The ancient-Roman historian Pliny (AD 23-79) describes that the discovery of glass was probably done about 5000 BC by Phoenician traders in the area of Syria. While cooking near or maybe even on top of their merchandise, nitrate stone blocks. The blocks melted, the melted material mixed with the sand and formed a transparent glassy substance!
Now 7000 years later glass is one of the most important materials we know. It is used for many different purposes around the house and in all industrial sectors.    
White wine glasses of the 
Chef&Sommelier series
(Arc International)
White wine glasses of the  Chef&Sommelier series (Arc International)


The glass formula

Everyday glass, the so called soda-lime glass, is made out of sand (silica or silicon dioxide), soda (sodium carbonate),and limestone (calcium carbonate). These materials are mixed and then heated up in an oven until the molten mixture has a temperature up to1675°C. At these temperatures the liquid has a low enough viscosity, so that it can easily be handled (blowing, pouring, forming, etc.).
 
Little changes in the formula have sometimes great effect on the properties. 
So do trace impurities in the raw materials cause that the glass can have a slight, unwanted color. For instance, glass becomes slightly green from Iron oxide in the sand. When a little Manganese oxide is added the glass becomes colorless again.
On the other hand are metal oxides used to make colored glass. Addition of Copper oxide colors glass light blue, Cobalt oxide gives glass a dark blue color and by adding Gold red glass can be made. (See also our colored glass page for more info.)

Another example of an additive which changes the properties extensively is Lead oxide. Lead oxide lowers the melting temperature and makes the final product softer. The reduction of the hardness makes the final glass easier to cut and therefore this lead oxide containing glass, or crystal, is used by crystal manufacturers. Another effect of lead oxide is that the refractive index, a measure for the 'sparkle, increases. (For more information about crystal see 'What is Crystal').

Crystal Artware - a vase by Artel
Crystal Artware - a vase by Artel


The addition of Boron oxide has a positive effect on the thermal shock resistance. It also makes the glass more resistant to corrosion. This type of glass is usually used for technical purposes like laboratory glassware but also in the house it can be found as bakeware. (See also the page 'Borosilicate glass'.)
Barium oxide is added to glass to increase the absorption of X-ray. It also increases the refractive index a bit. Because it's ability to absorb X-ray this type of glass is used for TV-screens (the old type!).

For sheet glass a little Magnesium oxide is usually added to the basic formula and for hollow glassware a little aluminium oxide, to give it the right properties.
A typical formula for packaging glass is: 74 SiO2, 13 Na2O10.5 CaO, 1.3Al2O30.3 K2O, 0.2 SO3 and 0.2 MgO.     

The glass industries 

Glass is a bulk product. Most people know that glass is used for windows, as a packaging material, for tableware and jewellery but glass is used for many other products.
The glass industry can be divided into four sectors:
                                                                        - Flat glass industry (or sheet glass industry)
                                                                        - Hollow glass industry
                                                                        - Fibre glass industry
                                                                        - Special applications

First factory of Riedel Glas Austria
(1760)
First factory of Riedel Glas Austria

The flat glass industry is the largest component of the glassware industry. Sheet glass is used in the construction of buildings, as windows, wall panels and facades for sky scrapers. Another big business for flat glass is the use as windshields in the automotive industry. All mirrors are made from flat glass and many furniture like tabletops.
A quickly growing part of this industry sector are the solar panels.

The second largest sector of the glass industry is the holloware sector. The holloware sector is responsible for all the packagings like bottles and jars, and that what we call glassware, like tableware, barware, vases, etc. The featured companies in our World of Glassware are all from the holloware sector.

Fibre glass, from the fibre glass sector, is used for making glass wool, which is used as an insulator in the construction and also as one of the basic materials for new composites. 
Another important product of this sector is the fibre optics. All data transfer, telephone and internet, which used to go through copper wire goes more efficiently through fibre optics. Hence all copper wire networks are replaced by fibre optics.

The last and smallest sector of the glass industry is the 'special applications'. In this sector we find producers of lenses, radiation shielding and other technical applications. The production of jewellery stones is also a part of this sector and some of the featured companies in our World of Crystal belong to this sector.

As you can see there is a lot of glass used for many purposes. If you want to read more about the glass industry then a portal like www.glassonline.com is interesting to visit or a site like wikipedia.