Flat glass
Flat glass is found in virtually every building these days. Right from transparent walls, to windows and even doors such glass is used. Many modern restaurants and cafes use such flat glass to spruce up the look of their interiors. In most office spaces, flat glass is used too. In automobiles, this kind of glass is widely used in the windshields.
Origins of flat glass
It seems the first people to recognize and make flat glass were the Romans. In fact, ruins at Pompeii show that the bathhouses in those times had flat glass like glass on them. This had a blue-green color to it.
What is it made of
Flat glass is a kind of safety glass, which can either be as per the laminated glass structure or as in tempered glass. In laminated glass, there is a polyvinyl butaryl or PVB film present in the middle flanked on either side by two or even more pieces of glass. This lends the glass a high tensile strength, which prevents the glass flying off even on impact. In the case of tempered glass the glass is heated to a high temperature and then quickly cooled off. This lends high strength to the glass. Flat glass is found in both these varieties.
Process of manufacture
There are many different methods of manufacturing flat glass. There is the rolling method, also known as figure rolling or rolled plate. Then there is the overflow downdraw, broad sheet, blown plate, cylinder blown, window crown, fourcault, machine drawn and cylinder sheet process as well as plate polishing technique. All of these are industrial techniques and there are specialized machinery for conducting such processes.
Float glass technique
There is also one other technique commonly used to make flat glass called float glass process. The central place where all the activity takes place is inside a tin bath. Here the hot and molten glass flows out from the furnace into the bath comprising molten tin. This molten glass flows evenly into the bath in a ribbon-like formation. Once the molten glass has accumulated on the tin bath it is cooled gently through the passage of nitrogen and hydrogen. The rate at which the hydrogen flows is determined by oxygen carry-over and dissolved sulphur inside the glass. In fact, if there is more sulphur and oxygen dissolved then there will be more need of hydrogen to facilitate reaction. This reaction will eventually result in flat glass. The incoming nitrogen will help to dilute hydrogen to a 4 or even 10% concentration. If the concentration of hydrogen is high inside it will cause bubbles underneath the glass. Here, the hydrogen comes out from the tin. One of the main purposes of the environment inside the tin bath is to prevent infiltration of air inside. This is achieved by preventing the float tank to exit outside. Through this method, flat glass is manufactured. At times, the glass maybe bent to be suitable for a different end usage. The common kinds of flat glass are called soda lime glass.
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