Advantages and Production Process of Float Insulated Glass
Release date:
2025-09-01
Currently, the glass used in the custom window and door manufacturing industry is all float glass. But what exactly is this type of float-insulated glass? And what are the key advantages of float glass? Let’s find out below:
Float glass:
Float glass was first introduced to China in the late 1970s when the Luoyang Glass Factory pioneered the adoption of a Royal Float Glass production line from the UK.
It is produced in a tin bath, where the glass floats on the surface of the molten tin. As a result, this type of glass boasts excellent flatness and is free from water ripples.
Used for mirrors and automotive glass—no distortion, which is one of its major advantages.
The mineral quartz sand used for float glass is of excellent quality. As a result, the glass produced is pure, brilliantly white, and boasts exceptional clarity—bright, colorless, and free from imperfections like glass inclusions or bubbles.
Float glass has a dense, heavy structure and feels smooth to the touch. For the same thickness, it’s heavier per square meter compared to flat glass, making it easy to cut yet highly resistant to breakage. All over 30 production lines across the country strictly adhere to national standards, ensuring this type of glass remains the top choice for residential construction.
Production process:
The forming process in float glass production is carried out in a tin bath filled with protective gases (N₂ and H₂). Molten glass continuously flows from the tank furnace and floats on the surface of the denser tin liquid. Under the influence of gravity and surface tension, the molten glass spreads evenly across the tin bath, flattening into a uniform sheet with smooth upper and lower surfaces. After hardening and cooling, the glass strip is guided onto a transition roller table. As the rollers on the table rotate, they pull the glass strip out of the tin bath and into the annealing lehr. Following annealing and cutting, the final product emerges as high-quality flat glass.
Compared to other forming methods, float glass offers several key advantages: it enables highly efficient production of superior-quality flat glass—free from wave marks, with consistent thickness, perfectly flat upper and lower surfaces, and precise parallelism. Additionally, the scale of the production line is not constrained by the limitations of traditional forming techniques, resulting in low energy consumption per unit of product. This method also boasts a high yield of usable finished products, making it easy to implement advanced scientific management practices and achieve full mechanization and automation—leading to significantly higher labor productivity. Moreover, the continuous operation cycle can extend for several years, ensuring stable, long-term production. Finally, float glass technology provides an ideal platform for manufacturing innovative new glass varieties on-site, such as electrically floated reflective glass, coated glass produced during annealing, and cold-end surface-treated glass products.
The forming process in float glass production is carried out in a tin bath filled with protective gases (N₂ and H₂). Molten glass continuously flows from the tank furnace and floats on the surface of the denser tin liquid. Under the combined effects of gravity and surface tension, the molten glass spreads evenly across the tin bath, flattening into a uniform sheet that gradually hardens and cools before being transferred onto a transition roller table. As the rollers on the table rotate, they pull the glass ribbon out of the tin bath and guide it into the annealing lehr. After annealing and cutting to size, the final product emerges as high-quality flat glass.
Compared to other forming methods, float glass manufacturing offers several key advantages:
- It’s ideal for efficiently producing premium-quality flat glass characterized by features such as the absence of wave marks, consistent thickness, perfectly flat upper and lower surfaces, and precise parallelism between them.
- The production line can be scaled up without being constrained by the limitations of traditional forming techniques, resulting in lower energy consumption per unit of product.
- It boasts a high yield of usable finished products, minimizing waste.
- The process is highly conducive to scientific management and enables full mechanization and automation, significantly boosting labor productivity.
- Continuous operation can extend for several years, ensuring stable and reliable production.
- Moreover, float glass production provides an optimal environment for manufacturing innovative new glass varieties on-site—such as electrically conductive reflective glass produced via the electrofloat method, coated glass with films applied during annealing, or cold-end surface-treated glass products.
What's the difference between ordinary flat glass and float glass?
Both ordinary flat glass and float glass are types of flat glass—though they differ in their manufacturing processes and quality.
Ordinary flat glass is produced by blending raw materials such as quartz sandstone powder, silica sand, potash feldspar, soda ash, and mirabilite according to a specific ratio. The mixture is then melted at high temperatures in a melting furnace and formed into transparent, five-colored flat glass using either the vertical draw method, the flat-draw method, or the roll-press method.
Ordinary flat glass is categorized into three grades based on appearance quality: selected grade, first-class grade, and second-class grade. It is also available in five thicknesses: 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm.
Float glass is produced by blending raw materials such as sea sand, quartz sand powder, soda ash, and dolomite in precise proportions. The mixture is then melted at high temperatures in a furnace, where the molten glass flows continuously from the tank furnace and floats on top of a layer of molten metal. This forms a uniform, flat glass ribbon that is polished with fire to achieve exceptional smoothness and clarity. After cooling and hardening, the glass is carefully detached from the metal surface, followed by annealing and cutting to create transparent, five-colored flat glass panes.
One of the standout features of float glass is its exceptionally smooth, even surface and remarkably consistent thickness, resulting in minimal optical distortion.
Float glass is categorized into three quality grades based on appearance: first-class, premium, and standard-grade products. Additionally, it is available in seven standard thicknesses: 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, and 12 mm.
The quality grade of ordinary flat glass is determined based on the number of defects such as wave marks, bubbles, scratches, sand particles, bumps, and streaks. For float glass, the quality grade is assessed according to the presence of defects like optical distortion, air bubbles, inclusions, scratches, streaks, and haze spots.
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