Most sheet glass made today using the float glass process. This process spreads molten glass over a bath of molten tin which is flat and very smooth. This allows the glass to form a sheet of glass with very flat surfaces on both sides. The process is a continuous one with molten glass flowing onto the tin which cools the glass as it moves along the bath. By the time that it reaches the end of the bath the glass has been made into a sheet of glass. The sheet is then cut into manageable sections for further processing or can be used immediately. During the cooling process, some of the tin will combine with the molten glass. This results in the side of the glass that was in contact with the tin fluorescing when lit by an ultraviolet light.