Home » Blog » How Toughened Glass is Made: The Process, Furnace Types, and Leading Machine Brands
Posted on : 10-07-2025 Author : Soumitra T
Toughened glass, also known as tempered glass, is a type of safety glass that is significantly stronger than regular annealed glass. It is engineered to withstand impacts, temperature fluctuations, and stress. Because of its durability and safe breaking pattern, toughened glass is used in buildings, vehicles, appliances, electronic devices, and furniture. Here we explores the step-by-step process of how toughened glass is manufactured, the types of furnaces used, and introduces some of the leading toughening machine brands around the world.
What is Toughened Glass?
Toughened glass is thermally processed to become up to 5 times stronger than regular glass. It is designed to break into small, blunt-edged fragments instead of sharp shards, which reduces the risk of injury. Step-by-Step Process of Making Toughened Glass
The process starts with annealed glass—a standard flat glass that is free from defects like bubbles or scratches. This glass is cut to the required dimensions because toughened glass cannot be cut, drilled, or altered once it is tempered.
The glass edges are polished or ground to prevent cracks from forming during the heating process. Holes or notches are also made at this stage, if required.
Before tempering, the glass is passed through a high-speed washing machine that removes all dirt, grease, or particles. Clean glass is essential to avoid imperfections and potential weak spots.
The clean glass enters a tempering furnace, where it is heated evenly to around 620°C to 700°C. The temperature must be precisely controlled so that the glass softens but does not deform. Heating usually takes 2 to 5 minutes, depending on the thickness (typically 4 mm to 19 mm).
Once the glass reaches the target temperature, it is immediately moved into the quenching section, where high-pressure air jets rapidly cool it from both surfaces. This sudden cooling causes the outer layers of the glass to solidify quickly, while the center remains hot and contracts as it cools. This forms a unique internal stress pattern:
Surface: Compressive stress
Interior: Tensile stress This stress profile is what gives toughened glass its strength and shatter-resistance.
After cooling, the glass is checked for:
Optical distortions
Surface defects
Stress uniformity (using a polarimeter)
Break pattern (on samples)
Defective pieces are rejected or recycled.
Different types of furnaces are used in glass tempering, depending on the product specifications and scale of operation.
Most commonly used. Glass is carried on heat-resistant ceramic rollers. Ensures flatness and uniform heating. Ideal for windows, doors, tabletops, etc.
Glass is suspended and passed vertically through the furnace. Eliminates roller marks. Suitable for thin, decorative, or etched glass.
Uses hot air circulation for even heating. Best for Low-E, coated, or reflective glass. Prevents surface damage from direct radiant heat.
Uses infrared lamps to heat the glass. Typically used in small batch production or R&D labs. Precise but less energy-efficient.
Combines convection and radiation heating. Offers flexibility and energy efficiency. Used for mixed production lines (clear, coated, and decorative glass).
Leading Toughened Glass Machine Brands When it comes to manufacturing high-quality toughened glass, the furnace technology plays a critical role. Here are some of the world’s top manufacturers of glass tempering machines:
1. Glaston (Finland): One of the most trusted brands globally. Known for its Glaston FC Series and RC Series. Offers energy-efficient, digitally controlled furnaces. Excellent support and precision engineering. Ideal for architectural, automotive, and appliance glass.
2. NorthGlass (China): A major supplier of high-capacity furnaces. Known for producing super large-size furnaces (up to 18 meters!). Cost-effective solutions for mass production. Popular in both Asia and Europe.
3. LandGlass (China): Specializes in continuous and flat-bending furnaces. Their Cyclone series is known for energy savings and consistent results. A top choice for architectural and insulated glass units (IGUs).
4. Mappi (Italy): Renowned for compact, high-precision tempering lines. The Fox and ATS series are used widely by small to medium glass processors. Focus on automation, quality, and space-saving designs.
5. HHH Equipment Resources (USA): North American manufacturer and distributor of glass tempering equipment. Provides comprehensive support and training. Focuses on medium-sized glass manufacturers.
6. Keraglass (Italy): Offers flexible systems for flat and bent glass. Strong in custom machinery for specialty glass applications.
Applications of Toughened Glass Buildings: Facades, partitions, doors, skylights
Automotive: Side and rear windows
Home appliances: Oven doors, refrigerator shelves
Furniture: Glass tables, shelves
Electronics: Mobile phone screens, monitor panels
Toughened glass combines strength, safety, and style. The process involves precise heating and rapid cooling using sophisticated tempering furnaces. The choice of machine and furnace type affects product quality, energy usage, and overall productivity. With growing demand for high-performance and safety glass, investing in advanced toughening technology from trusted brands like Glaston, NorthGlass, and LandGlass is essential for manufacturers looking to stay competitive. Whether you're designing a skyscraper or making an oven door, the strength of toughened glass and the machines behind it makes all the difference.
