How Glass is Made

Glass is made from very basic substances. But when those basic ingredients  go through our process, they transform into the durable and advanced building material that we love.

Take some high quality sand (the kind you’d imagine on your dream beach), soda ash, limestone, saltcake and dolomite and melt at white heat to a high consistency and you’ve got glass.

All those raw materials we mentioned before – we call them the batch. And the first thing we do is make sure the batch is up to scratch – that is, each component is measured out rigorously and blended to ensure the mix stays consistent and within our tight tolerances for these things. Only then can the batch pass through the furnace. 

We use world leading technology to apply coatings that impart clever thermal properties and other desirable benefits to the glass. There are a number of coatings that can be applied depending on the end-product. One common coating is low emissivity (Low E) coating, which could go on to improve the energy performance and comfort of your space, if the end-product ends up near you.

Another form of coating is the pyrolytic coating process – or so-called “hard coating” process – deposits and fuses microscopically thin layers of metal oxides to the surface of the glass, producing extremely durable coated products that can easily be handled, transported and processed.

Since the glass we send you isn’t generally still firing hot, you might have guessed we have a cooling process.

The annealing lehr, which is essentially a very long cooling rack for the glass “ribbon” produced at the hot-end of the process, removes stresses in the glass by carefully cooling it down from 600°C to room temperature. Careful controls applied in this process ensure that the glass can be smoothly cut when fully cooled – both for cutting the ribbon into the large stock sheets that come of here at the manufacturing line, and for all the subsequent cutting and processing of those sheets after they’ve been shipped out to processing factories.

This makes sure that in the end, you get a sheet of glass that’s of the highest standard for clarity, flatness, and edge quality, with almost no optical distortion and residual stresses in the glass.

After we determine that the batch is ready,an automated conveyor progressively adds the mix to the filling end of the gas fired regenerative furnace. The blank of solid granules of the newly introduced batch mix rest briefly on the surface of the already molten glass, before the 1550°C temperatures in the melter see them melt and combine. The molten glass stays in the furnace long enough to allow the components to combine and react together and allow bubbles of gas to escape – ensuring glass of consistent colour and density, and as free from distortion and faults as practically possible.

We make some glass in bulk so that it can be used by glaziers and fabricators to suit almost any use they need. We call these stock laminates. Essentially, they are big bits of glass stuck together with a polymer interlayer.

Laminating glass is the process of bonding two or more sheets of glass together, with an interlayer in between. As you might have guessed – all the glass in our range of stock laminates is laminated.  

Our stock laminates are sold out into the market as stock sheets which can be subsequently cut to the sizes and shapes needed for specific applications. In essence, they are a way of getting safety glass out into the hands of glaziers and fabricators in a form that they can modify themselves on site and even off the back of the truck if necessary. (This is in contrast to toughened glass, which is made in a toughening furnace and can’t be altered thereafter – so needs to be made in the right shape and size from the outset.)

Put simply, the laminating process creates glass which holds itself together if broken (rather than falling in a heap on the floor). Used appropriately it can act as a safety glass to protect people and possessions. Bulk laminate sheets offer a way making these properties available out in the market in a form which can be cut and shaped to the demands of specific projects.

You might have guessed the silvering process applies to mirrors, but there’s a little more to it than that.

Silvering is a process by which a thin layer of metallic silver is deposited on the surface of the glass. Left exposed, the silver would oxidise just as silverware tarnishes. To prevent this a special protective paint is applied specifically designed to maintain the look of the silver.

The same process that applies silver in the silvering process can be reprogrammed to apply matte colour. This produces an annealed, cuttable workable stock sheet of colour-backed glass for use where block colour with subtle surface reflection is desired.  Again, wardrobe doors are a common example..  

Equivalently, the same vinyl backing process is also available to prepare a product which stays in place if broken.

On top of standard mirrors, we also offer “vinyl-backed” safety mirrors.

Vinyl-backing involves applying a sheet of tough vinyl film on the back of the glass. This film acts in a manner similar to the interlayer material in a laminate – holding the glass in place if broken. This is ideal for use in sliding wardrobe doors.

Our custom processing allows us to create products that are bespoke to purpose. Through these processes we can transform glass into something that is particularly suited to a specific purpose in your home or office.

Cutting the glass is how we can give you the shape and style of glass you need.

But glass is a brittle material – if it starts to crack it tends to do so completely – so you might think this would make it difficult to cut. But this actually works to our advantage in the cutting stage – the glass needs only to be scored on the surface and then lightly pressured to break cleanly along that line.  (The neatness of that cut comes down to the amount of residual stress held in the glass as it was cooled at manufacture – so cutting quality and accuracy actually starts right back at the float line!)

Although you’d usually see glass in squares and rectangles, we can cut it into almost any shape you can think of. That being said, we know what works and what doesn’t when dealing with glass, so there are a number of cutting guidelines and limiting dimensions that we apply to ensure that the glass will perform well in practice.

Edgework is applied to glass to make it safer to handle, more resilient to damage and better to look at.

Any time you cut glass, you create an edge. As cracks in glass most commonly begin at the edges of the glass, the “quality” of the edge makes a big difference to the resilience of the glass overall. Any imperfection in that edge can provide a point where the stress generated by a load on the glass, even from something as small as someone leaning on it, can become concentrated and start a crack. So edges matter.

Technically the most resilient edge is the edge formed naturally when the glass is cut – a clean-cut edge. In a sense this is the state the glass “chose” to be in when it was scored and broken-out during cutting.

However, because of its near 90 degree corners, a clean-cut edge can be susceptible to crushing, chipping and other incidental damage during further handling, install, and use.

So we can take the sharp corners off the clean-cut glass (arising), or go further to create other forms of edges including rounded, mitred, polished – each suitable for different looks and purposes in the life of the glass. 

Many applications of glass call for holes notches and cut-outs to be incorporated into the final design, for example notches for hinges in frameless shower-screens, holes for power-points in splashbacks, cut-outs for pet-doors  and more.

All these things are possible, but just as with cutting and shaping the glass, there are various guidelines and limiting dimensions we adhere to when preparing the glass.

In almost all circumstances, glass with holes, notches and cut-outs will need to be toughened.

All architectural glass starts its life flat from the float line. But it can be bent to suit purposes like creating curved windows, food display cabinets, or balustrades.

It’s a process similar to the initial stages of toughening. A pre-cut or shaped piece of glass is heated to the temperature at which it just starts to cease being solid, and is then rolled backwards and forwards over rollers which have a prescribed curvature in them. From that, you end up with a curved sheet of glass.

Heat treatment refers to Toughening, Heat-Strengthening or Heat Soaking.

Toughening and Heat-Strengthening are essentially the same operation but applied to a different degree. Glass is heated in a specially designed and highly controlled furnace to a point where it just starts to cease being solid, and is then rapidly cooled with air.  

This sets stresses within the body of the glass which act to compress the outside few millimetres of the glass. This effectively makes the glass able to “bend” further before it cracks.

The more stress set in the glass, the greater the load it can withstand before breaking. Toughened glass can withstand approximately five times the load of ordinary glass before breaking. Toughened glass can also withstand higher temperature differences across the surface of the glass without breaking due to thermal expansion – making it perfect for splashbacks for instance.

However, the stresses “locked-into” the glass mean that the glass can’t be further altered – attempting to cut or alter the shape of the glass will almost certainly cause it to break.

If toughened glass is broken, it releases a great amount of energy very quickly –  generating the characteristic breakage pattern of toughened glass, where the glass forms small cubes of glass rather than the sharp shards you’d expect from non-toughened glass. 

Heat Strengthening

Heat Strengthened glass is almost exactly the same as toughened, but the cooling process is less intense. This results in glass which is less strong, but breaks with less energy, so you get  larger “plate-like” sections that tend to stay in place, rather than crumble away.  

Heat Soaking

Heat Soaking is a process for confirming the absence of specific physical contaminants and imperfections in toughened glass that may cause it to “spontaneously” break throughout its life.  This phenomenon is extraordinarily rare, but in many applications it is worth taking steps to all but eliminate this possibility – that’s where heat soaking comes in.

The heat soaking process seeks to simulate conditions where spontaneous breakage could occur if the imperfection was to be present in the toughened glass. That way, any glass will break in the heat-soak oven in the factory, not after it has been installed.

IGUs – Insulating Glass Units – is a fancy, more formal, title for double glazing (or triple or beyond!).  Manufacturing insulating glass units involves bringing together two pieces of glass, both adhered to a spacer. So essentially we create a sandwich of glass:gas:glass.

This is a factory-sealed unit, assembled in controlled conditions, for quality-assured performance and long-life. Various glass types, spacer materials, and gasses can be combined to deliver different appearances, properties, and thermal performance levels depending on what the glass is going to be used for.

We like to think of this as the icing on the cake – the finishing touches in the form of applied treatments and additions to the glass that can be added to enhance its performance in use. 

We can apply a number of additional treatments to change the functionality and finish off your glass.

There’s a number of preparations and chemical treatments that can be applied to glass post-processing. 

One of the most common is painting – colour-backed glass finds its ways into many thousands of homes and other buildings every year as splashbacks and wall panelling.  Other treatments applied in the factory can impart properties to the glass to make it water repellent, easier clean, and lower in condensation.

Some uses of glass call for specific visibility motifs to be applied to the glass – this can be achieved by screen printing the surface with a special ceramic paint (generally prior to toughening) or with an adhesive design. 

Self-adhesive films that cover the whole surface of the glass are also available – these offer a range of benefits including protecting the surface from vandalism and other damage.  They can also play a role in security and impact protection as part of an purpose-designed system.