Heat-strengthened (HS) glass has been subjected to a heating and cooling cycle ans is generally twice as strong as annealed glass of the same thickness and configuration. HS glass must achieve residual surface compression between 3,500 and 7,500 PSI for 6mm glass, according to ASTM C 1048. 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 and initially may remain in the glazing opening.
This type of glass is intended for general glazing, where additional strength is desired to withstand wind load and thermal stress. When heat-treated glass is necessary, SGI Industries recommend the use of heat-strengthened glass for application that do not specifically require a safety glass. HS glass cannot be cut or drilled after heat-strengthening and any alterations, such as edge- grinding, sandblasting or acid etching can cause premature failure.
SGI heat strengthened glass with its lower processing temperature gives the façade less optical distortion. This process makes the glass approximately twice as strong as annealed glass of the same thickness and also exhibits greater resistance to thermal stress when compared to normal glass or annealed glass>
According to the Standards, unless this type of processed glass is laminated, it cannot be considered a safety glass, enables glass to break into larger pieces and remain in the window frame. We recommend the glass be laminated.