Tempered glass

Description

A high strength Plate glass that has been reheated and held above its annealing point (650C or 1200F), then flash cooled. Tempered glass was first used in 1942. The tempering process makes the glass 3-5 times stronger than ordinary plate glass of the same thickness (Konrad, 1995). However, it cannot be cut, shaped, drilled, or ground. On impact or damage, the entire piece of tempered glass will shatter into small, granular pieces with round-edges. Tempered glass is typically used for large doors and windows, display cases, tables, shelves, aquariums, refrigerator trays, cookware, and mobile screen protectors. Automobile windows are also made of tempered glass with the windshields having an additional laminated layer to provide containment of the particles when shattered.

Synonyms and Related Terms

vidrio templado (Esp.); verre trempé (Fr.); gehard glas (Ned.); vidro recozido (Port.); vidro temperado (Port.); heat-strengthened glass; hardened glass; toughened glass; safety glass; Tuf-Flex [Libbey-Owens-Ford]; Herculite [PPG]

Environmental Risks

Tempered glass is not recyclable.

Physical and Chemical Properties

The glass has tensile stresses within the body that are balances by compressive stresses on the surface. When viewed through a polarizing filter, tempered glass shows variations in stress

Working Properties

Can not be cut or shaped. Must be made to size and shape prior to tempering.
Smoothing edges and drilling holes must also be done prior to tempering.
Tempered glass is most susceptible to failure due to damage at the edge.

Resources and Citations

Wikipedia: Tempered glass Accessed Oct. 2023
K.Konrad, K. Wilson, W. Nugent, F.Calabrese, "Plate Glass", in Twentieth-Century Building Materials, T. Jester (ed.), McGraw-Hill: New York, 1995.
Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
Thomas C. Jester (ed.), Twentieth-Century Building Materials, McGraw-Hill Companies, Washington DC, 1995
Encyclopedia Britannica, http://www.britannica.com Comment: "industrial glass." Accessed 2 Dec. 2004.