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 alehr. The finished product has near-perfect parallel surfaces.
The side of the glass that has been in contact with the tin has a very small amount of the tin embedded in its surface. This quality makes that side of the glass easier to be coated in order to turn it into a mirror; however that side 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.
Laminated glass is manufactured by bonding two or more layers of glass together with layers of PVB, under heat and pressure, to create a single sheet of glass. When broken, the PVB interlayer keeps the layers of glass bonded and prevents it from breaking apart. The interlayer can also give the glass a higher sound insulation rating.
There are several types of laminated glasses manufactured using different types of glass and interlayers which produce different results when broken.
Laminated glass that is made up of annealed glass is normally used when safety is a concern, but tempering is not an option. When broken, the PVB layer prevents the glass from breaking apart creating a “spider web” cracking pattern.
Tempered laminated glass is designed to shatter into small pieces, preventing possible injury. When both pieces of glass are broken it produces a “wet blanket” effect and it will fall out of its opening.
Heat strengthened laminated glass is stronger than annealed, but not as strong as tempered. It is often used where security is a concern. It has a larger break pattern than tempered, but because it holds its shape (unlike the “wet blanket” effect of tempered laminated glass) it remains in the opening and can withstand more force for a longer period of time, making it much more difficult to get through.
Toughened (or 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. Using toughened glass on automobile windshields would be a problem when a small stone hits the windshield at speed, as it would shatter into small squares endangering the driver and passengers. In commercial structures it is used in unframed assemblies such as structurally loaded applications, frameless doors, and vision sidelites adjacent to doors. Toughened glass is typically four to six times the strength of annealed glass.
Insulated glazing, or double glazing, consists of a window or glazing element of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space between the layers. This type of glazing has functions of thermal insulation and noise reduction. When the space is filled with an inert gas it is part of energy conservation sustainable architecture design for low energy buildings. Insulated glass is most typically used in storefront framing and curtain walls.
Heat-strengthened glass is glass that has been heat treated to induce surface compression, but not to the extent of causing it to “dice” on breaking in the manner of tempered glass. On breaking, heat-strengthened glass breaks into sharp pieces that are typically somewhat smaller than those found on breaking annealed glass, and is intermediate in strength between annealed and toughened glasses.
Starfire glass features a clearer surface. Starfire glass does not change the color of anything behind it. As clear glass gets thicker the green cast becomes more noticeable. Sometimes this is not important, but if you want to display true colors that are seen through glass,starphire glass is key in allowing to do so. The use of Starfire glass keeps the colors true to life. Starfire glass is a lead free, low iron product that represents the very best in glass. A slight blue tint is evident in the mostly-clear products, so it is not clear enough to be called “crystal”, but its properties hold for much clearer viewing than regular glass.