Float glass is the industry standard, all-purpose clear glass. It may be used as-is or as a base for processing into laminated, tempered, acid-etched, and other processed glass forms. Float glass is generally available in both clear and tinted varieties — clear float glass is transparent, and allows for the transmission of most light on the visible spectrum. Tinted float glass, produced by adding different colouring agents to the glass mix, is slightly more opaque and emphasizes distinctive tones of grey, green, blue, or bronze.
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Float glass is manufactured by pouring molten glass material into a chamber containing a large, shallow pool of molten tin. The effect of the molten glass on the tin is similar to that of oil on water. The molten glass “floats” atop the aluminum (hence the name float glass), spreading evenly so it can be cooled into a uniform sheet. The float process is also referred to as the Pilkington Process, named for the Pilkington brothers, who created the manufacturing process in the mid 20th century. Good quality clear float glass is free from imperfections and distortions, and provides a flat, transparent surface, allowing up to 92 percent of visible light to pass through, depending on the thickness. Tinted float glass of similar quality lets in less light due to the presence of colour additives, making it a good candidate for applications where privacy is a consideration.
The thickness of float glass is determined at the time of manufacture and can vary significantly depending on the intended use. Typically, float glass is manufactured in thicknesses from 1.7mm to 25mm. Very thin float glass, less than 5mm, is typically found in small-scale applications such as commercial picture frames, display cases, and household decor. Very thin float glass is also being increasingly used in technology applications, including phone and TV screens. Medium thicknesses may be used in residential applications such as shower doors and windows, while thicknesses 15mm and up are generally reserved for special purposes and upscale developments.
Clear float glass is prized for its high level of light transmission, and the ease with which it can be tempered, tinted, and otherwise altered to produce a more aesthetically interesting appearance, such as through acid etching or patterning. Since float glass is so widely used and in-demand, it is common for glass manufacturing plants to produce this type of glass on a continuous basis. The process of floating, cooling, and cutting the molten glass can continue 24 hours per day, 365 days per year.