Heat-strengthened (HS) 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.
- HS 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.
- HS glass is intended for general glazing, where additional strength is desired to withstand wind load and thermal stress.
- HS glass does not require the strength of fully tempered glass and is intended for applications that do not specifically require a safety glass product.
- HS 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.
The requirements on heat-strengthened glass and the properties are defined in the EN 1863.