Tempered/Heat Strengthened Glass


Glenny Glass is proud to have state-of-the-art convection furnace technology capable of heat treating almost any flat glass product made.We have the largest furnace in the midwest capable of tempering up to a 106" x 142" size.
There are two different types of heat-treated glass, tempered glass and heat strengthened glass.  Tempered glass is 4 to 5 times stronger than annealed or untreated glass and heat strengthened glass is twice as strong.  tempered glass is used in safety glazing applications and meets the requirements of both CPSC 16 CFR 1201 and ANSI Z97.1.  Heat Strengthened Glass is used where addditional strength is required for thermal stress or wind pressure.
Glenny Glass fabricates tempered and heat strengthened glass on our 2 state-of-the-art TCME tempering furnaces.  Both furnaces utilize high convection technology which allows us to accurately control temperature and air flow in multiple heating zones.  The glass is conveyed into heating chambers where is oscillates on ceramic rollers until it reaches a temperature of approximately 1200°F.  The glass exits the heating chambers and enters the quench chambers where the glass is rapidly cooled.  Tempered Glass is cooled very rapidly and with a very high volume of air through a series of nozzles directing air to the top and bottom sides of the glass.  For heat strengthened Glass the cooling process is slower.  Heating in the furnaces is monitored by Raytek thermal imaging scanners allowing us to maintain consistent glass surface temperature.  Optical distortion inherent in the heat treating process is monitored by LiteSentry Osprey digital imaging scanners allowing us to adjust parameters and minimize distortion.
Tempered Glass, when broken, fractures into small pieces, reducing the likelihood of injuries.  For some applications in windows, doors, railings and shower enclosures, tempered glass is required by building codes.  Tempered Glass is used in many other applications including table tops, counter tops, partitions, shelving and similar applications.
Heat strengthened glass will break in a pattern similar to annealed glass.  When broken, the glass fragments tend to stay in the opening longer than fully tempered glass particles.
With both tempering and heat strengthening, optical distortion is a possibility.  Because of the very high processing temperatures, the glass is inherently susceptible to roller wave, bow and warp while it is being heat treated.  All these can result in optical distortion, but optical distortion can occur for many other reasons including, glazing pressure, wind load, temperature changes, barometric pressure changes or even changes in altitude between our fabrication facility and where it is installed.
Safety is a prime consideration when determining the type of heat treated glass required for a particular application.  Contact us to review your project requirements.

Ask us about:

  • Tempering