Glass sheets and plate glass consist of flat glass materials in the form of thin or wide slab planar structures. Glass sheets and plate glass are commonly used in architecture as windows, transparent walls, and glass doors. They are also used in automotive and marine applications, for car and boat windows and windshields. Glass sheets and plate glass are also used in industrial applications, including as covers for meters or as optical glass windows.
Glass sheets and plate glass, also simply called flat glass, is typically made using float glass technology. In the float glass process, a layer of melted glass is poured onto a molten tin surface, forming a smooth, uniformly thin layer. The tin bath is progressively cooled until the glass layer can be removed onto rollers for further cooling and processing. Glass sheets and plate glass made using the float glass process are usually made from soda ash, sand, limestone, dolomite, and sodium sulfate. The addition of other elements may enhance the characteristics of the glass or give it a specific color. Glass sheets and plate glass can also be manufactured by other processes, including rolling; overflow downdraw, which is used to make flat panels for displays; blown plate, which is used to make mirrors; broad sheet; cylinder blown; and many others.
Glass sheets and plate glass come in a wide variety of shapes, sizes, thicknesses, and with a multitude of physical and chemical characteristics. Glass sheets and plate glass can be clear or transparent, or treated with other elements to give an opalescent or iridescent quality. The glass can also be textured or patterned to obscure images behind the glass, while still allowing light through, providing a measure of privacy. Dichroic glass is glass that has been layered with metal oxides to give the glass a unique color and texture.
Other glass sheets and plate glass are made for special purposes, such as bulletproof glass or tempered glass. Bulletproof or bullet resistant glass is made by using layers of glass sheets or by using a transparent polycarbonate thermoplastic. Tempered glass is stronger and more durable than regular glass sheets and plate glass. Tempered glass is used in a wide variety of products, including vehicle windows and specialty items like scuba diving equipment, marine vehicles, and some cookware. Tempered glass is made by heating and then rapidly cooling the glass to induce residual compressive stresses in the surface of the glass. The glass will not break until the residual compressive stresses are exceeded. Tempered glass sheets and plate glass are designed to fracture into small fragments rather than shards, minimizing the likelihood of injury.
Glass sheets and plate glass can also be strengthened chemically using an ion exchange process. In this process, the glass is immersed in a molten bath of alkali salt that contains ions larger than the ions in the glass. The smaller sodium ions in the glass are replaced with the larger ions in the molten salt. The larger ion induces strain in the structure, strengthening the glass material.