1-Whats the Float Glass or Flat Glass 

   Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and various low melting point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces.[1]

Modern windows are made from float glass. Most float glass is soda-lime glass, but relatively minor quantities of specialty borosilicate[2] and flat panel display glass are also produced using the float glass process.[3] The float glass process is also known as the Pilkington process, named after the British glass manufacturer Pilkington, which pioneered the technique (invented by Sir Alastair Pilkington) in the 1950s at their production site in St Helens, Merseyside.

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Types of Glass From the Float Process

There are two types of glass made by the float process, clear glass and tinted glass. Most of the flat glass made by the float process is clear glass. As its name implies, clear glass is transparent and colorless. Depending upon its thickness, clear glass allows about 75 to 92 percent of the visible light to pass through.

Tinted glass (also called heat absorbing glass) is made by adding coloring agents to the batch mix. These agents include bronze, gray, green and blue. As the glass gets thicker, the density of the color also increases. This causes the glass to transmit less visible light. The light transmittance of tinted glass varies from 14 to 83 percent depending upon its color and thickness.