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Clear Float Glass VS Tempered Glass

Views: 11     Author: Site Editor     Publish Time: 2023-11-23      Origin: Site

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We draw on our expertise as glass line manufacturer through this article to provide a comprehensive guide to distinguishing between clear float glass and tempered glass, focusing on their pros and cons and best use cases.

What is clear float glass?

Clear float glass is produced through the float glass manufacturing process, a method widely used in the glass industry.

In a float glass production line, the process begins with raw materials such as silica sand, soda ash, limestone, and other additives being mixed and melted in a furnace at extremely high temperatures. The molten glass is then fed onto a bath of molten tin, forming a continuous ribbon that floats on the tin surface due to its lower density. As the glass ribbon moves along the tin bath, it undergoes controlled cooling, annealing, and polishing processes. This results in a flat, distortion-free sheet of clear glass with uniform thickness and excellent optical quality, which is called clear float glass.

clear float glass

Advantage of float glass

1. The surface of float glass is very flat and smooth.

Since the float glass manufacturing process involves floating the molten glass on a bath of tin, this helps create glass with minimal defects. This meticulous production method not only enhances the beauty of the glass but also adds to its versatility. The smooth surface of float glass makes it ideal for a variety of uses, such as windows and display cabinets, where clarity and original finish are crucial for visual appeal.

2. High transparency, good visibility and aesthetics.

Float glass typically has a light transmittance of over 90%, making it ideal for scenes that require clarity and clear views. This advantage is particularly valuable in architectural and design contexts where light-filled and visually appealing spaces are required, making float glass the first choice for projects that emphasize transparency and brightness.

3. Float glass is more economical.

On the one hand, because the process is simpler, the cost of float glass itself will be lower than that of tempered glass;

On the other hand, even after forming, it can be cut or even reprocessed according to size and shape requirements. The flexibility of reprocessing enables cost-effective customization options for a variety of projects.

Shortcomings of float glass

1. Float glass is not as safe as tempered glass and has greater safety risks.

When float glass breaks, sharp glass fragments are produced, and the fragments are large, creating a safety hazard. Therefore, sometimes additional processing is required, such as adding a frame or using a mezzanine to make it safer.

2. Float glass has lower strength than tempered glass. 

Since there is no tempering treatment, it is more likely to break when impacted by external forces.

What is tempered glass?

Tempered glass is created by heating and rapidly cooling high-quality float glass. It can be said that if there is no float glass production line, tempered glass may not be made.

The process involves cutting the glass to the desired size and shape, polishing the edges, and removing impurities, etc. The glass is then sent to a tempering furnace where it undergoes rapid cold extraction, creating thermal stress differences between the surface and interior. This increases the glass's hardness and stress, resulting in tempered glass.

Advantages of tempered glass

1. Tempered glass is different from ordinary glass in that it is not prone to cracking or shattering due to exposure to high temperatures.

This is because the tempering process increases the strength of the glass and increases its heat resistance. This allows tempered glass to be used in environments where heat is a concern, such as near stoves or fireplaces.

2. Tempered glass is great for thermal insulation and has excellent insulation properties.

On the one hand, tempered glass is generally thicker than ordinary glass, which can reduce heat loss and achieve better thermal insulation effects. On the other hand, during the production process of tempered glass, a layer of good compressive stress is formed on the surface of the glass, making the thermal expansion coefficient of tempered glass smaller than that of ordinary glass, thereby reducing heat transfer.

3. Tempered glass leads the way in terms of safety.

When tempered glass breaks, the fragments will not form a sharp shape like float glass, but will take on the appearance of a cube, and the fragments will be very small, which greatly reduces the risk of injury to people near the glass. This makes tempered glass a common choice for applications where safety is a priority, such as shower doors or car windows.

tempered glass

4. Tempered glass has high strength and excellent impact resistance.

Because tempered glass has experienced intense heating and rapid cooling during the production process, its strength is five to six times that of float glass, and it has strong impact resistance and scratch resistance. Therefore, it is often used as a choice for glass doors, storefront windows and other areas with a higher risk of damage.

Shortcomings of tempered glass

1. Further processing of tempered glass is limited.

Once tempered glass is formed, it cannot be further processed such as cutting, drilling, or it will break into small pieces. This limitation can be a significant disadvantage if the glass installation requires a custom shape or size. This makes planning the design before making tempered glass crucial.

2. The edges of tempered glass are easily damaged.

When tempered glass is under pressure, the external force must first offset the compressive stress on the surface of the glass, thereby improving the load-bearing capacity of the glass. From this we can know that the reason why tempered glass has good impact resistance is that its surface has compressive stress.

However, the corner areas of tempered glass tend to have stress concentration and are relatively fragile areas, so they are easily broken when knocked on the edge.

For example, the side window glass of a car is tempered glass. The instructions for using the escape hammer say to tap the corners of the side window glass. The reason is that tapping the corners of the side window glass will easily cause cracks in the glass, and the stress release will cause the entire glass to break. It becomes a slag for easy escape.

3. The transparency of tempered glass is lower compared to float glass.

The light transmittance of tempered glass is above 80%. The main reason why tempered glass is less transparent than float glass is that the tempering process can cause some deformation or slight clouding, which will affect the clarity of the glass.

4. The cost of tempered glass is higher than float glass.

The additional manufacturing process and enhanced strength and safety features result in a higher price for tempered glass.

5. Tempered glass may undergo sudden, spontaneous breakage.

If the installation gap is relatively small when installing tempered glass, or the tempered glass is in direct close contact with the frame, due to the different expansion coefficients of different materials, it is easy to cause extrusion deformation between the glass and the frame when temperature changes occur, causing the tempered glass to break. This means you need to be more professional and careful when installing tempered glass.

In addition, if the original glass piece of tempered glass has more impurities and bubbles, the higher the self-explosion rate. Therefore, it is very important to choose a good manufacturer.

Key differences between Clear Float glass and Tempered glass

The following summarizes the characteristics mentioned above in table form to more clearly show the main differences between clear float glass and tempered glass:


Clear Float Glass

Tempered Glass

Production Process

Manufactured through the float glass process involving high-temperature melting on a bed of molten tin.

Produced by heating and cooling high-quality float glass, followed by a tempering process for added strength.

Surface Characteristics

Very flat and smooth surface due to the float glass manufacturing process.

Smooth and polished surface with enhanced strength and safety features.

Transparency and Visibility

High transparency with over 90% light transmittance. Ideal for applications requiring clarity and clear views.

Above 80% light transmittance, slightly lower than float glass due to the tempering process, but still suitable for various applications.


More economical as the manufacturing process is simpler.

Higher cost due to additional processing and enhanced features like strength and safety.

Safety Features

Breaks into large, sharp shards, posing safety risks.

Shatters into small, relatively harmless pieces, reducing the risk of injury.


Lower strength compared to tempered glass. More prone to breakage upon impact.

Higher strength, five to six times that of float glass. Excellent impact resistance and scratch resistance.

Customization and Alteration

Can be cut or reprocessed according to size and shape requirements after forming.

Cannot be cut or drilled without breaking into small pieces.

Heat Resistance

Typically used in applications with lower heat exposure.

Higher heat resistance, suitable for environments where heat is a concern, such as near stoves or fireplaces.

Applications of Float glass and tempered glass

From the above list of the advantages and disadvantages of the two types of glass, it is not difficult for us to summarize the application scenarios of float glass and tempered glass.

Float glass is often used for standard windows where safety concerns are minimal and cost is important. It is also commonly used in homes, buildings, or picture frame glass where safety regulations do not require the additional strength of tempered glass. Where safety glass requirements are not a priority, float glass may be a cost-effective option.

window glass

Tempered glass is the preferred choice for shower enclosures, exterior doors and windows, automotive windows, glass railings, tabletops and countertops, electronic equipment and storefronts due to its enhanced security features and resistance to breakage. Because of its strong wind pressure resistance and protective effects, it is widely used in glass curtain walls of high-rise buildings.

building glass

How to differentiate between tempered glass and float glass

In addition to distinguishing tempered glass and float glass by observing the manufacturer's mark and the shape after damage, we can also distinguish the two through the following methods:

1. Check the edges of the glass.

Tempered glass edges are usually darker or a different color than float glass edges. The tempering process changes the edge appearance.

2. Use polarized lenses or look at the glass diagonally through sunlight.

When viewed through polarized light, tempered glass may exhibit stress patterns that appear as colored bands or irregularities.

3. Can test the resistance of glass.

Tempered glass is more resistant to impacts, scratches and thermal stress than float glass.

4. Use the scratch test, but use this method with caution.

While not foolproof, float glass surfaces are generally more susceptible to scratches than tempered glass. If appropriate, perform a small, inconspicuous scratch test.

5. Because tempered glass is fired at high temperatures, the surface flatness will change.

Basically, the surface of tempered glass below 10 mm will have a slightly wavy state, while the surface flatness of float glass will be higher than that of tempered glass.

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