How is glass produced?

Glass is a versatile material with many uses, from the screens of our smartphones to glass partition walls in an office. Glass is made from natural raw materials, which are abundantly available. Additionally, it is a material that can be recycled and reused, helping reduce waste.

How is this transparent and versatile material made? In this guide, we look at how glass is manufactured and the different types of glass produced for glazing.

But first, what is used to make glass?

What is glass made of?

Glass is made by melting sand (silica) and mixing it with soda ash (sodium carbonate) and limestone (calcium). The melting point of sand is around 1,700 degrees. The soda helps to reduce the sand's melting point to save energy. While limestone makes the glass stronger and water resistant.

Other substances or chemicals can be added during production to produce glass variations. For example, cobalt salt makes a blue-tinted glass.

How is glass manufactured and formed?

The sand, soda ash and limestone are heated in a furnace and become molten liquid. During production, recycled or broken glass (cullet) is normally added to the mix to reduce waste and energy consumption. The mixture then cools and solidifies to become glass.

Glass is structurally similar to liquids at high temperatures but behaves like solids at lower temperatures. Technically, glass is an amorphous solid where the atoms and molecules are not arranged in regular arrays.

Glass can be shaped and formed using different techniques. For example, blowing air into the molten glass and shaping it by manipulating it while it is still hot and pliable, usually to form bespoke, handmade items such as jars and drinking glasses.

Another technique is moulding. This involves pouring or pressing the molten glass into moulds to form containers, bottles, and other household items.

Glass can also be poured to produce flat sheets - called float glass. Float glass is the most common form of glass produced and can be used to make mirrors, windows, car windshields, glass balustrades and partitions.

How is float glass produced?

Float glass sheets are formed by pouring molten glass onto a molten liquid-metal bath - often a metal with a low melting point, like tin. The molten glass does not mix with the liquid metal and forms a floating ribbon with a smooth, flat surface on both sides and an even thickness.

The temperature is slowly reduced so rollers can pull the glass ribbon off the bath at a controlled speed. Changing the speeds allows for glass sheets of varying thickness, normally ranging from 2mm to 19mm.

Annealing glass

When glass is heated and cooled rapidly, it can develop internal stresses and is very brittle. To avoid this, the glass is slowly cooled - a process called annealing. The glass is passed in an annealing oven or kiln, known as a lehr, to reduce the internal stresses created during production.

Cutting and finishing glass

Once the annealed process has been completed, glass sheets can be cut to size as needed. Additionally, the sheets may be finished to meet specific requirements, such as polished edges or toughening.

Types of glass used to construct glass partition walls and balustrades

Float glass, once annealed, is commonly used to make windows. By adding additional manufacturing processes, float glass can be used as a base product to make other types of glass, such as toughened or laminated glass, common in partitions and balustrades.

Toughened or tempered glass

The toughening glass process uses annealed float glass sheets, cut to size and heated evenly to temperatures above 600C, then rapidly cooled. The glass becomes hardened and significantly stronger and more durable.

Toughened or tempered glass is sometimes referred to as safety glass. It is harder to break. When broken, it shatters into small chunks or cubes of glass rather than sharp-edged shards, reducing the likelihood of serious injury.

TIP: If you want to know if a glass panel is toughened, look for the BS EN number (normally on the corner or side of the glass). If the number is BS EN 12150, then the glass is thermally toughened safety glass.

Laminated glass Laminated glass is made by bonding two sheets of glass with a tough PVB interlayer. These panels are tough to break, and even when broken, the interlayer can hold the panel in place, making it ideal for glass balustrade systems, walk on glass floors and stairs.

Acoustic glass partitions are laminated glass panels with an acoustic resistance interlayer specifically made to help reduce noise transmission. Similarly, bulletproof glass is made of multiple layers of glass and interlayers bonded together.

If you want to know more about the different types of glass and their uses, see our guide on the difference between float glass, toughened glass and laminated glass.

Fire-rated glass

Fire-rated partition glass panels are made using several layers of toughened glass bonded with intumescent interlayers. In the event of a fire, the intumescent interlayer will swell or expand due to heat exposure, helping to slow the spread of fire and smoke.

Panels can also be manufactured with a wire frame. This wire frame helps to hold the panel in place during a fire. Fire-rated glass and partitions have different ratings which measure the integrity, radiation control and insulation. You can find out more in our guide on fire resistant glass partitions

Summary

Glass is made by melting sand, soda ash and limestone. When cooled, it solidifies and can be used in buildings in many ways, such as windows, office glass partitions or glass balustrades. Glass can be treated to be strengthened and bonded with interlayers for additional safety and uses, such as acoustic glass.

If you're wondering what type of glass you need for your next home project or office refurb, call us at +44 (0)208 947 8428 (office hours are Monday to Friday, 9 am to 5 pm). Or, write to us via our contact page.

About the writer: Paulo Ferreira has extensive experience in project management and worked at Prism Glass for two years, where he managed glass installation projects and day to day operations. He also has extensive experience in financial services. His skills include graphic design, branding, content marketing and blogging.

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