Glass is one of the basic industrial and construction materials. Transparency of glass is a qualitythat enables us to use it in a number of branches. As for its chemical composition, it usually contains silica sand, soda, oxides of alkali metals, calcite and other admixtures/additions/, according to the qualities desired. It is biologically inactive material. It´s not freely decomposable in the nature. It cannot be found in the nature therefore it must be produced. Glass in produced industrially for various purposes (decoration, construction material, packing material, automotive and engineering industry).
There are many admixtures added into glass in order to achieve the required qualities according to the purpose of use.
Flat glass (sheet glass, plate glass)is mostly used in the building industry and automotive industry. Flat glassdoes 1/3 of the world glass production. The world annual productionof flat glass does about 48,000,000 tons. Due to its qualities,which enable us to use it in thebuilding or automotive industry, its productiongrows by 6 % a year.
We must realize that the smelting furnace for flat glass works continuously, with the capacity of up to 1000t of molten glass / day. In case that the sales are low, the glass is being broken and the shards are molten down and returned back to the production process. This is how primary sources of raw material are saved up to 40%.
However, there is no flat glass production (float glass) in Slovakia. All flat glass is being imported from the Czech Republic, Poland, Hungary and Ukraine.
Flat glass is processed by various methods in order to achieve desired qualities. One of them is the heating-up of glass to very high temperatures. We call this process glass hardening or tempering. Tempered glassusually breaks into many pieces. These pieces are not sharp and one does not get hurt if being hit by them.
