90% of the world's flat glass is produced by the float glass process invented in the 1950s by Sir Alastair Pilkington of Pilkington Glass, in which molten glass is poured onto one end of a molten tin bath. The glass floats on the tin, and levels out as it spreads along the bath, giving a smooth face to both sides. The glass cools and slowly solidifies as it travels over the molten tin and leaves the tin bath in a continuous ribbon. The glass is then annealed by cooling in an oven called a lehr. The finished product has near-perfect parallel surfaces. A very small amount of the tin is embedded into the glass on the side it touched. The tin side is easier to make into a mirror. This "feature" quickened the switch from plate tofloat glass. The tin side of glass is also softer and easier to scratch. Glass is produced in standard metric thicknesses of 2, 3, 4, 5, 6, 8, 10, 12, 15, 19 and 22 mm. Molten glass floating on tin in a nitrogen/hydrogen atmosphere will spread out to a thickness of about 6 mm and stop due to surface tension. Thinner glass is made by stretching the glass while it floats on the tin and cools. Similarly, thicker glass is pushed back and not permitted to expand as it cools on the tin.
It is a sandwich made of one piece of plastic Poly Vinyl Butyral between two or more glasses. The PVB sticks with the glass, forms chemical as well as mechanical bonds. When laminated with annealed glass, the layer maintains the geometric integrity of the pane in case of breakage. Also it gives acoustic insulation as well as gives protection against damage caused due to UV radiation because it cuts almost 99% of UV radiation present in the sunlight. A Laminated glass is regarded as a safety glass by most of the standards. Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered.
Also known as tempered glass is a type of safety glass that has increased strength and will usually shatter in small, square pieces when broken. It is used when strength, thermal resistance and safety are important considerations. At home you are likely to find toughened glass in shower and sliding glass patio doors. In commercial structures it is used in unframed assemblies such as frameless doors, structurally loaded applications and any glass where there is a danger of human impact. Toughened glass is typically four to six times the strength of annealed glass.
Although toughened glass is most susceptible to breakage via edge damage, breakage can also occur from impacts in the centre of the glass pane. Tempered glass is made from normal annealed glass via a thermal tempering process in which the glass is subjected to heat till its softening point and then rapidly cooled. This gives the glass its strength. A fully tempered glass is 4 to 5 times stronger then an annealed glass of similar thickness. A fully tempered glass is regarded as a safety glass and when it breaks it disintegrates into small blunt pieces which greatly reduce the chances of injuries and if there are any then they are superficial in nature.
Ordinary tinted glass is popular because it reduces heat gain and carbon emmissions, although it also marginally reduces visible light transmission.High Performance or Low-e tinted glass or spectrally selective tinted glass reduces solar heat gain to below that of ordinary bronze/ gray tint but has a visible transmittance closer to clear glass. The tint has little effect on the U-factor but reduces solar gain considerably, which can reduce the need for air conditioning in the summer. Tinted glass is useful in controlling glare - especially for those windows facing east or north east. Return the sunlight not glare into your home!
Features and Benefits of Tinted Glass:
Tinted glass can reduce UV transmittance and visible light, so when strategically placed, it will reduce the transfer of heat and improve comfort. In fact, tinted glass can reduce the solar heat transmission by 30-50% when compared to ordinary clear float glass, especially if used in an insulated glass unit for double glazed windows and doors. The solar energy is attracted to the darker shade of glass and is absorbed while the air draws this heat away from the building and its users. Also, it can be an alternative to Low-e glass in double glazed units, when glass colour is important.
