Float glass – is a sheet glass which is manufactured by using the method of thermoforming on the molten metal. This method is the most modern in the manufacture of sheet glass, as well as the most popular. This method is also called the float method. Float glass is a basis for the production of a large number of new and improved multiple glass units and it is also often used in laminated glazing. This type of glass is characterized by low optical distortion, excellent surface quality and uniform thickness.
M1-M2 marks of the float glass have high light transmitting capability, glossy surface and excellent optical properties – this glass does not distort the image.
Float glass is used in the construction industry, furniture industry and the automotive industry as a source material. It is also the source material for its derivatives such as energy-saving glass mirror cloth, etc. After passing through the various kinds of processing, float glass takes the form of finished products, which is constantly in our everyday lives. It can be multiple glass units, furniture, decorative glass, or full glass constructions.
Float method appeared in 60-th. Company “Pilkington” has developed this method, which gave impetus to its further use in production. That’s when many countries around the world began to produce float glass using a new method based on the float bath filled with molten tin.
Here are the main stages of the float glass production:
1. Molten glass falls into the float bath from the glass furnace. Float bath has a protective nitrogen-hydrogen atmosphere and is filled with molten tin.
2. Due to the forces of gravity, surface tension, and because of the fact that the molten glass spreads over the surface of molten tin with no problems, perfectly flat glass surface forms.
3. Next, tape glass mass either stretched or its spreading limited in order to get the glass of desired thickness. Typically, the float glass has a thickness of about 3-19 mm. Of course, it is possible to go beyond that, but in the construction, according to the rules, the thickness of glass must not be less than 3 mm. Showcases glass is a sheet of glass whose thickness exceeds 8 mm.
4. Due to the spreading glass mass forms a continuous band, which floats on the surface of molten tin. Then it’s removed and put to the annealing furnace. This stage is very important in the float glass manufacturing process. During the annealing of glass tension, which is accumulated as a result of fairly rapid cooling, lessens. This stress can negatively affect the mechanical strength of the glass.
Process of annealing of float glass itself has its own peculiarities. For example, cooling or heating of the manufactured products goes with the highest possible speed in order to avoid breakage. The temperature is chosen specifically in order to prevent deformation of the product and provide the necessary speed to eliminate temporary stress at the same time. Next the product is gradually cooled – at this point the lowest annealing temperature is reached. It does not allow new temporary stresses to occur again. Rapid cooling takes place last; the speed of the process at this stage is limited only by the thermal stability of the product. Eventually, finished float glass is cut and packaged.
