Chemical composition of glass

A glass is an inorganic non metallic material that does not have a crystalline structure.  Such materials are said to be amorphous and are virtually solid liquids cooled at such a rate that crystals have not been able to form.

Typical glasses range from the soda-lime silicate glass for soda bottles to the extremely high purity silica glass for optical fibers.  Glass is widely used for windows, bottles, glasses for drinking, transfer piping and recepticles for highly corrosive liquids, optical glasses, windows for nuclear applications etc. etc.

In history most products have been blown glass.   In recent times most flat glass has been produced using the float process.   Mass produced bottles and decorative products are made using industrial scale blown glass process.  Hand blown glass items are made in art/craft centers throughout the world.

The main constituent of glass is silicon dioxide (SiO 2).  The most common form of silica used in glassmaking has always been sand.

Sand by itself can be fused to produce glass but the temperature at which this can be achieved is about 1700o C.  Adding other chemicals to sand can considerably reduce the temperature of the fusion.   The addition of sodium carbonate ( Na 2 CO 3), known as soda ash,in a quantity to produce a fused mixture of 75% Silica (SiO 2) and 25% of sodium oxide (Na 2O), will reduce the temperature of fusion to about 800o C.   However, a glass of this composition is water soluble and is known as water glass.   In order to give the glass stability, other chemicals like Calcium Oxide (CaO) and magnesium oxide (MgO) are needed.   The raw materials used for introducing CaO and MgO are their carbonates, limestone (CaCO 3) and dolomite (MgCO3), which when subjected to high temperatures give off carbon dioxide leaving the oxides in the glass.