Tempered glass is a safety glass whose durability is enhanced by a special heat treatment. Glass sheets are heated to approximately 650–700°C and then rapidly cooled by high-speed air blowing. This process creates a tight compressive stress on the outer surface of the glass and a tensile stress in the inner part, significantly increasing its fracture resistance. It is 4 to 5 times more durable than standard flat glass. This structure has made its use widespread, especially in areas requiring safety and impact resistance.

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Physical and Mechanical Properties

Tempered glass exhibits high resistance to impact, bending, and thermal shocks. When broken, it shatters into small, non-sharp pieces, which makes it advantageous for safety. For example, while a normal flat glass is likely to crack with a sudden temperature change of 150°C, tempered glass can withstand sudden temperature changes up to 250–300°C. Additionally, the bending strength of tempered glass is generally above 120 MPa, although it varies depending on the type of glass.

Quality Control and Test Methods

Quality tests are mandatory after the tempering process. The most common tests include:

• Thermal Shock Test: Measures the glass's resistance to temperature differences.
• Impact Test (Hammer or Ball Test): The fracture behavior of the glass is observed by dropping a hammer or metal ball from a certain height.
• Fragment Count: Fragments scattered in a 5 cm x 5 cm area are counted. For example, in flat glass with a thickness of 4–12 mm, this number should be a minimum of 40.
• Bending Test: The flexibility limits of the glass are measured.
• Optical Quality Tests: Visual distortion, glare, and light transmittance are checked.

Surface Treatments and Innovative Production Techniques

Recently developed partially matted tempered glass with reduced surface roughness offers both aesthetic and functional advantages. Special chemical polishing processes with hydrofluoric acid (HF) increase the glass's transmittance rate to 90.4% and its gloss to 33.7. These glasses show twice the scratch resistance of matted glass (0.8 N). Additionally, features such as "anti-fingerprint" and "anti-glare" are added, providing functional value, especially in white goods and interior design.

Vision-Based Quality Control Systems

Today, manual controls such as human eye-based crack counting in tempered glass are being replaced by systems based on image processing techniques. Embedded systems consisting of cameras, light platforms, and morphological analysis algorithms work with grayscale simplification, contour determination, and shape classification steps. These systems have a 91.1% success rate and largely eliminate human error.

Areas of Use

Tempered glass is used in many areas, from the construction industry to transportation:

• Architecture: Facade claddings, glass balconies, glass railings.
• Interior Design: Shower cabins, glass table tops, showcases.
• White Goods: Oven doors, glass hob surfaces.
• Transportation: Vehicle windows, train and aircraft interior partitions.
• Security: Inner layer of bulletproof glass combinations.

Tempered glass can be colored, patterned, or combined with laminated structures to offer more advanced security solutions, depending on the requirements of its application area.