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Float Glass

   GOLDEN FAITH FLOAT GLASS is a sheet of glass made by floating the molten glass on a bed of molten tin. This method gives the glass uniform thickness and very flat surfaces.
       Float glass is made by melting raw materials consisting of sand, limestone, soda ash, dolomite, iron oxide and salt cake. The raw materials are mixed together and fed into a large furnace that is natural gas or fuel oil fired. The raw materials, referred to as batch, blend together to form a large pool of molten glass. The molten glass is fed into the float bath (tin bath) through a delivery canal. The amount of glass allowed to pour onto the molten tin is controlled by a refractory gate called a tweel. The tin bath is provided with a protective atmosphere consisting of a mixture of nitrogen and hydrogen to prevent oxidation of the tin. The glass flows out onto the tin surface forming a floating ribbon with perfectly smooth glossy surface on both sides with an even thickness of approximately 4 mm. Thinner glass is made by stretching the glass ribbon to achieve the proper thickness. Thicker glass is made by not allowing the glass pool to flatten to 4 mm. Machines called attenuators are used in the tin bath to control both the thickness and the width of the glass ribbon.
      As the glass flows down the tin bath, the temperature is gradually reduced until the sheet can be lifted from the tin onto rollers. It then passes through the lehr where it is further cooled gradually so that it anneals without strain and does not crack from the change in temperature. The glass travels down the rollers in the lehr for about 100 metres and comes out at the "cold end" where it is cut by machines.
      Some tin is absorbed into the glass, and with a proper ultraviolet light a sheen can be seen which differentiates the tin from the non-tin side.