What Is Float Glass (and How Is It Made)?

what is float glass

Float glass describes the high-quality, extremely smooth, and distortion-free type of glass used extensively in (amongst other things) windows and doors. In fact, whichever type of glass you have in your house, it’s highly likely it comes from the float style of manufacturing…

The production of this material involves the process of pouring molten glass onto a bed of molten tin, allowing it to float and spread out, resulting in a uniform thickness and surface. It’s the most popular type, followed by sheet glass which we explained here.

Float glass is the base material for diverse glass products like tinted glass, laminated glass, and tempered glass so can provide you with high-end, functional products way beyond your creative imagination.

The Pilkington Process

Float glass is a type of glass commonly used in windows and other applications where a smooth and distortion-free surface is desired.

It was invented by Sir Alastair Pilkington in the late 1950s as a result of his search for a more efficient and higher quality glass-making process. The Pilkington Process involves floating molten glass on top of molten tin, which creates a smooth and uniform surface.

This technique doubtlessly revolutionised the glass industry and is the primary method used today for producing many styles of glass.

Raw Materials and Composition

The primary raw materials used to produce float glass include sand, limestone, silica, and dolomite.

These components are combined in specific proportions to create a glass-making mix, which is then melted in a furnace at high temperatures. The glass mixture may also be adjusted with other materials, such as sodium carbonate and sodium sulphate, to improve its physical and chemical properties.

Additionally, colourants and refining agents can be added to achieve desired colours and a higher level of purity.

Here’s the science bit…

The production of float glass involves a sequence of carefully controlled steps:

  1. Melting: The raw materials are melted in a furnace at temperatures of around 1500-1600°C.
  2. Flow onto molten tin: The molten glass flows from the furnace onto a bed of molten tin through a ceramic spout lip. Nitrogen and hydrogen are sometimes used to control the atmosphere in the chamber and prevent the tin from oxidising.
  3. Formation of glass ribbon: As the glass floats on the tin, it spreads out and forms a flat, even ribbon. Rollers are used to control the thickness of the glass, which can vary between 0.4mm to 25mm.
  4. Annealing: The glass ribbon slowly moves through a kiln, where it is gradually cooled to release internal stresses and strengthen the glass.
  5. Inspection and cutting: The cooled glass is inspected for defects before being cut into standard sizes or custom shapes.

The result is a high-quality, distortion-free glass that can offer homeowners many advantages when used for double glazing, such as increased strength, durability, and a smooth surface for clear, unobstructed views.

Float Glass Characteristics

Thickness and Width

This glass type oozes versatility as it comes in a range of thicknesses and widths to suit your needs.

The production process allows for precise control over thickness, resulting in uniform and parallel surfaces. Common thicknesses include:

  • 2mm-4mm: suitable for picture frames and display cases
  • 5mm-6mm: suitable for windows and doors
  • 8mm-12mm: suited for thicker applications like tabletops or balustrades

…not forgetting, customised widths that can cater to specific requirements, offering flexibility in design and application.

Optical Qualities

One of the significant advantages of float glass is its optical clarity.

The manufacturing process ensures an extremely smooth, distortion-free surface that provides unobstructed views when used in windows and doors. It’s clarity and transparency make it an ideal base material for other glass types, such as:

  • Tinted glass: heat-absorbing and energy-efficient
  • Laminated glass: added safety and noise reduction features
  • Tempered glass: increased strength and thermal resistance

But just how durable is float glass?

Known for its strength and durability, it’s a great choice for all manner of designs. More substantial than plate glass without compromising its thickness, the result is a dense and super durable product.

Some key durability features of float glass include:

  • Scratch resistance: the smooth surface is resistant to scratches, making it easy to clean and maintain
  • Annealing: a heat treatment process that removes internal stresses, improving the glass’s resistance to breakage
  • Polishing: refined edges created through polishing, enhancing safety and aesthetics

When treated further, the glass can be converted into toughened or tempered glass, which offers even greater durability and safety. Tempered glass is heat-treated to increase its strength, making it more resistant to breakage and less likely to cause injury when broken, as it shatters into small, granular pieces.

Overall, float glass combines thickness, width, optical qualities, and durability to create a versatile material for using in your home design; from windows and doors to safety glass and energy-efficient solutions.

Float Glass Uses

Windows and Doors

Float glass, known for its smooth surface and distortion-free appearance, is widely used in windows and doors. Its crystal-clear transparency will provide you with unobstructed views and bright natural light entering your home.

Float glass can also be transformed into heat-absorbing tinted glass or laminated glass allowing you enhanced safety, not to mention energy efficiency too.

Mirrors and Furniture

The sleek and uniform nature of float glass makes it an ideal choice for manufacturing mirrors and glass furniture components. Its pristine appearance adds a touch of elegance and sophistication to decorative pieces, such as mirrors, tabletops, and shelving units.

High-Rise Buildings

In high-rise building construction, float glass is a popular choice due to its strength, durability, and ease of maintenance. Its ability to withstand extreme weather conditions and resist scratches ensures a long lifespan, making it a cost-effective solution for architectural purposes.

Vehicle Glass

Automobile manufacturers often utilise float glass for producing vehicle windows and windshields. The glass’ smooth surface ensures a clear, distortion-free view for drivers, while its strength contributes to the overall safety and structural integrity of the vehicle.

Soundproof Glass

Float glass is also used as a base material for creating soundproof glass, which is essential in applications where noise reduction is crucial. By incorporating multiple layers or additives, float glass is transformed into a versatile and noise-reducing material, suitable for environments such as recording studios, offices, or residential buildings.

What are the advantages of Float Glass?

Customisation Options

Float glass offers a range of customisation options, making it a versatile material throughout your living space.

The crystal-clear transparency of float glass is ideal for displaying items, such as in retail shop windows, showroom display cases, and countertops, effectively showcasing the beauty of products like expensive watches and jewellery.

Moreover, float glass can be transformed into other forms such as tinted glass (heat absorbing) and laminated glass, catering to different needs.

Low Cost and Availability

One of the significant benefits of float glass is its low cost, which makes it widely available and highly accessible.

Since it is the most common type of glass used in the building industry, float glass can be found in windows, windshields, and other applications. It’s relatively low production cost, combined with its durability and strength, makes it an economical choice for all sorts of projects.

Thermal Stress Resistance

Float glass’s thermal stress resistance adds to its appeal.

The clever manufacturing process enhances the glass’s resistance to thermal stress, as it can withstand wear and tear, making it an excellent choice for projects exposed to the elements, such as windows and outdoor furniture.

Furthermore, the glass’s smooth surface makes it easy to clean, promoting a low-maintenance approach to decorative glassware.

In summary, float glass offers significant advantages, such as customisation options, low cost, and thermal stress resistance.

These features contribute to its widespread use in various applications and industries, making it an especially popular choice for double glazing projects.

Disadvantages of Float Glass

Safety Concerns

While float glass, made up of soda-lime glass, has some strength and durability, it is not as strong as other glass types, such as tempered glass or laminated safety glass.

When it breaks, it can form sharp shards, posing a significant safety hazard.

This makes it unsuitable for certain high-risk applications, necessitating the usage of alternative glass types, like safety glass or laminated safety glass, which offer better resistance to impact and shattering.

Another safety consideration is the limited resistance to heat and extreme temperatures that float glass has compared to other options, such as insulated glass.

For buildings with high exposure to sunlight, using tinted or frosted glass can be a more appropriate choice to control heat absorption and glare.

Environmental Factors

Float glass manufacturing demands significant amounts of energy and raw materials. For instance, soda ash (sodium carbonate) and sodium sulphate are used in large quantities as refining agents in the process.

This high-energy production can contribute to environmental concerns, such as greenhouse gas emissions and natural resource depletion. Additionally, during the manufacturing process, rejected or recycled float glass, known as cullet, can generate significant waste if not properly managed.

Given the significant specific gravity of float glass, the weight of heavier panes can lead to increased consumption of fuel for transportation, contributing to further environmental concerns.

Round Up: Is Float Glass Good?

While the low production costs of float glass do make it an attractive option for many applications, the environmental factors can negate some of its advantages in certain circumstances.

When summarising the pros and cons of float glass it’s transparent – the advantages outweigh the disadvantages. 

The clarity of this high-end product makes it a forerunner for creative architectural features in any living and working space. 

However, it can’t be ignored… float glass brings with it, some safety and environmental concerns.

You’ll want to consider all your options before making a decision to utilise this product into your home-design. 

If float glass proves to be a desirable choice for you then you’ll be embracing durability, energy-efficiency, low maintenance and stunning aesthetics.  That much is clear.

Matt James
Matt James

Hi, Matt here! I started out almost 20 years ago as a teenager working in the family business fitting doors, windows and conservatories. I now run this website to share the best tips and advice for anyone looking to get a good deal on double glazing.

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