Heat-strengthened glass has been subjected to a heating and cooling cycle and is generally twice as strong as annealed glass of the same thickness and configuration. Heat-strengthened glass must achieve residual surface compression between 3,500 and 7,500 PSI for 6 mm glass, according to ASTM C 1048. Please contact Guardian regarding thicker glass standards.
- Heat-strengthened glass has greater resistance to thermal loads than annealed glass and, when broken, the fragments are typically larger than those of fully tempered glass.
- Heat-strengthened glass is not a safety glass product as defined by the various code organizations.
- Heat-strengthened glass is intended for general glazing, where additional strength is desired to withstand wind load and thermal stress.
- Heat-strengthened glass does not require the strength of fully tempered glass and is intended for applications that do not specifically require a safety glass product.
- Heat-strengthened glass cannot be cut or drilled after heat-strengthening and any alterations, such as edge grinding, sand blasting or acid etching, can cause premature failure.
When heat-treated glass is necessary, Guardian recommends the use of heat-strengthened glass for applications that do not specifically require a safety glass product.