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Heat Strengthened Glass

• Knowledge > Glass > Heat Strengthened Glass

What is heat strengthened glass?

• Standard: BS EN 1863 for heat strengthened soda lime silicate glass.
• Heat strengthened glass is producing by slowly heating, and then quickly cooling, annealed glass. The cooling process is more rapid than for annealed glass but not as rapid as for toughened glass. The speed of cooling determines the strength - the quicker the cooling, the stronger the glass.
• There are no internationally-recognised standards for heat-strengthening and it should be noted that US glass is generally strengthened to a ‘higher’ standard than European glass, resulting in a product which is much closer to thermally toughened glass than European heat strengthened glass.
• In North American terminology, heat strengthened glass is sometimes referred to as "partially tempered" glass.

Advantages of heat strengthened glass

• Heat strengthened glass is stronger than annealed glass of the same thickness.
• Heat strengthened glass does not suffer from the problems associated with NickelSulfide inclusions.

Disadvantages of heat strengthened glass

• Heat strengthened glass is not a safety glass. It breaks into shards in the same manner as annealed glass.
• Heat strengthened glass is generally more expensive than thermally toughened glass of the same thickness. This is due to the time and care needed to control the cooling process.

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