Heat Strengthening is appropriate for many applications and materials where a full temper is not possible or desired due to thickness, size, low thermal expansion rate of the base material, or other application requirements. This process does not produce a full “dicing” pattern when the glass is broken and will not meet the requirements of ANSI Z97.1 or CPSC 16CFR1201. Where appropriate, ASTM-C-1048 “Kind HS" may apply.
Heat Tempered soda-lime glass is about four times stronger than annealed glass and can handle approximately 2 to 3 times the thermal shock of annealed glass. Heat tempered glass effectively withstands bending, impact and rapid temperature change because the surface has been put into a state of compression. That process involves heating the glass at about 1200F in a tempering oven. In addition to improved strength, tempered glass is also safer because, if broken, it crumbles into small pieces instead of sharp shards, also known as dicing. Heat tempering can cause some optical distortion. Where optical change is not acceptable, chemical strengthening may be more suitable. Heat tempering is typically appropriate for glass from 1/8″ (3.2mm) - 3/4 (19mm) thick and sizes from 1″ diameter to 92″ x 144″. Heat tempered glass may be verified by performing a surface compression test or break pattern test for compliance. Heat Tempering is appropriate where compliance to any of the following standards is required…
ANSI Z-26.1 – 1990 for Safety Glazing Materials used in Motor Vehicle Equipment. DOT Certified.
Chemical Strengthening is appropriate for thin soda-lime glass or complex-shaped parts where minimal optical distortion is required or additional impact strength is desired, especially for glass materials thinner than 3mm. It provides up to 5 times the impact strength of annealed soda-lime glass. Glass strengthened by this process will not “dice” and therefore cannot be used in those applications requiring small shards. Chemically strengthened glass may be specified according to ASTM-C-1422. Our maximum size for chemically strengthened glass is 28” x 36”. Typical cycle is 8 hours. Enhanced cycle time of 16 hours may be required depending on application.