Float Glass is made by a process which creates perfectly smooth, flat and clear glass.
In a contained atmosphere of 100% nitrogen, a thin layer of molten glass is poured onto a tank of molten tin. Being less dense than the tin, the glass floats at the top and forms a perfectly smooth, glossy surface on both sides and maintains an even thickness. Besides the fact that this creates the smoothest, most clear glass possible, it is more economic than grinding and sanding.
After the glass is poured onto the tin, it is slowly cooled. The sheet is then put onto tin rollers and cooled gradually. Otherwise, cracks and imperfections would result if it annealed, or changed from liquid to solid, too quickly. The nitrogen is present so that the glass will not oxidize and no longer be transparent. The process allows some tin to be absorbed into one side of the sheet of glass, but it is only visible under an ultraviolet light.
For centuries prior to the development of float glass, crown glass was the most common form of window making. In that process, one would blow a bottle or crown shaped glass. It would then be cut before it hardened into a relatively flat piece. That would then be spun in a manner similar to a potter’s wheel until flat. A window pane could then be cut from it, and it would harden. Besides being a more difficult and labor-intensive process, the resulting glass had many imperfections.
Float glass was invented at Pilkington Brothers, an English glass manufacturer in the mid 1950’s by Alastair Pilkington (no relation). The process was not made public until 1959. Until that point in the 20 th century, glass was formed as a puddle on a solid iron surface, ground down to a flat surface and polished until gleaming.
Low-E Glass has a thin layer of oxidized metal on one side of it. This makes a glass that is a useful insulator. Heat and light are allowed into a room or building, but the thin sheen on the inner side will not allow it back out. The glass is still transparent both ways. The metal oxide can either be applied as soon as the sheet of glass leaves the tin bath or afterwards with magnetically-enhanced cathode sputtering. The name “Low-E” stands for Low Emission and refers to the low levels of heat and light emitted from your home after entering through the Low-E glass.
There are many varieties of Low-E depending upon your climate or needs.
All Climate, All Season: This type of glass maximizes the temperature you set either by heating or air-conditioning (or both) in your home. It allows light in but insulates from excessive heat entering or heat escaping.
Solar Control: Solar Control glass is engineered for the maximum insulation from the sun’s rays and maintenance of cool air from air conditioning. It isn’t tinted at all at resembles normal glass.
Glare Control: This type of glass does have a small amount of tint. What it does is absorb the light from the sun, muting its sharp rays and only allowing a soft glow to permeate your home. The glass will be warmer to the touch than normal glass, but not to a dangerous degree.
Winter Climate Glass: Winter Climate Glass offers the best protection from cold air. It allows for the most penetration of warmth and sunlight while offering a seal that won’t let as much warmth from heat escape.