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Heat-Treated Glass

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Insulite utilizes three cutting-edge electric horizontal oscillating furnaces to fabricate tempered glass. These furnaces are capable of tempering flat float glass products ranging from 1/8” (3mm) to 1/2” (12mm) in thickness. Notably, each furnace is equipped with two hearths, ensuring enhanced productivity. Additionally, the inclusion of aspirators enables a smoother tempering process for the latest generation of post heat-treatable vacuum deposited reflective and low-e glass products, currently available in the market.

The furnaces are utilized to heat the glass to a consistent temperature of approximately 1200 degrees Fahrenheit. Ceramic rolls are employed to convey the glass through the furnace at carefully controlled speeds, ensuring uniform temperature distribution and minimizing any visual distortions. The heat-strengthening process closely resembles tempering, but with a slightly slower cooling cycle, resulting in surface compression levels that are lower than those found in fully tempered glass.

Heat-strengthened glass possesses roughly twice the mechanical and thermal strength of annealed glass of the same thickness. When heat-strengthened glass breaks, it typically forms larger pieces akin to the break pattern of annealed glass, although other breakage patterns are also possible, as shown on this page. This type of glass is commonly used in areas where additional strength is needed but with a larger break pattern compared to tempered glass. This ensures that if the glass breaks, it will remain in the opening until it can be safely replaced. Heat-strengthened glass is commonly employed in spandrel glass locations. Notably, it cannot be cut or drilled after undergoing the heat-strengthening process.

Heat-strengthened glass fails to comply with safety glazing standards outlined in ANSI Z97.1 and CPSC 16 CFR 1201.

Regarding optical quality:

Some noticeable bowing, warping, and process roll distortion may be observable. These imperfections stem from the inherent nature of the manufacturing process and fall within the acceptable boundaries defined by ASTM Standard C1048.

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Traditional Impact Load

Picture Frame



Enhanced Strength and Properties:

This glass substrate exhibits heightened mechanical and thermal strength compared to annealed glass while still preserving its regular properties like chemical resistance, hardness, expansion, and deflection. Notably, it delivers double the thermal and mechanical strength when compared to annealed glass of equal thickness.


Break Pattern Similar to Annealed Glass:

The break pattern of this glass resembles that of annealed glass, with large pieces being formed upon breakage. The size and shape of these pieces are influenced by various factors, including the applied load, the point of origin of the break, and the temperature of the glass.

Rare Spontaneous Breakage:

Spontaneous breakage caused by machining or edge treatments is an infrequent issue with this glass variety.

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