Heat-Strengthened Glass

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.

Fully tempered glass is approximately four times stronger than annealed glass of the same thickness and Configurations  and residual surface compression must be over 10,000 PSI for 6mm according to ASTM C1048. According to ASTM C 1046, fully tempered glass must 7800 kgf/cm2 to max of 24400 kgf/cm2. When broken, it will break into many relatively small fragments which are less likely to cause serious injury.

The typical process to produce tempered glass involves hearing the glass to over 1,000 degrees Fahrenheit then rapidly cooling to lock the glass surfaces in a state of compression and the core in a state of tension as shown in the diagram. Tempered glass is often referred to as  “safety glass” because it meets the requirement of the various code organizations that set standards for safety glass.

Tempered glass is intended for general and safety glazing such as sliding doors, swing doors, building entrances, barth and shower enclosures, interior partitions and other uses requiring superior strength and safety properties.

Tempered glass cannot be cut or drilled and any alterations. Such as edge-grinding, sandblasting or acid-etching can cause premature failure.

Fully Tempered glass from GLASTON (HELSINKI FINLAND) ANSI Z 97.1 must have a capacity energy efficient frequency converter controlled blower system for thick glass tempering up to 19mm thickness.

SGI tempered glass also called toughened glass, makes the glass four to five times stronger than annealed glass thickness. This process gives the glass greater resistance to thermally induced stress than annealed glass.  Tempered glass typically breaks into small granules which are considered harmless and is best suited to be used as safety glass.