A history of glazing – how glass became a construction material

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In our modern world, glass is something most of us take for granted, and many people rarely stop to think about. But the world of glazing is constantly evolving, and even in the last few decades, huge leaps have been made in what can be achieved with glass in construction.In our modern world, glass can be used for everything from cutting-edge architecture to modest home improvements. New technologies mean that things like insulation are now industry standard measurements.

But how did we get to this stage? How has glass come all the way from the crude windows of centuries ago, to the awe-inspiring structural wonders we now see on a daily basis? And what are the implications for the future of construction, both in our homes, and our society in general?

What is glass?

In layman’s terms, glass is simply liquid sand that has been reformed. Sand is made up mainly from silicone dioxide, which melts at a rather warm 1700 degrees C. When it cools down, the molecular structure of the sand is completely reconfigured to form what we recognise as glass.

The result is a material that’s both strong, and highly practical. Because glass can be either completely clear, or coloured for more creative use, it’s been a staple of the construction industry for centuries. But the use of glass more broadly dates back even further:

The birth of glass

Humans have been using glass as a practical material for, astonishingly, thousands of years. Obsidian – a naturally occurring glass formed by sand melting as a result of volcanic eruptions – was used as a material to create spear tips.

The earliest evidence for man made glass goes back as far as 4000 BC. Archaeologists have found that evidence for glass being used in a simple way to coat stone beads for decoration. By 1500 BC, the use of glass had advanced, and people had created a way to make hollow containers by pouring molten glass over a shaped central core of cold sand and clay. Crude it may be, but this was nonetheless the start of one of the biggest developments in construction for humankind.

How was glass made?

Possibly the most interesting thing about the development of glass from a basic crafting material to an intrinsic part of construction, is the change in the ways in which it has been made. As with all raw materials, our ability to manipulate glass has evolved over centuries, which has in turn led to entirely new possibilities.

Throughout history, the basic processes in glass making have been improved and honed significantly. The very earliest uses of glass involved molten sand that was almost always applied and shaped, in a variety of ways, around a ‘core’ piece. While techniques in glass creation did advance, it wasn’t until the 1st Century BC that a significant leap was made in the form of glass blowing.

Discovered by the Romans on the Syro-Judean coast, glass blowing completely changed both the use and perception of glass as a construction material forever. Blown glass vessels became cheaper to produce than pottery, and in some respects, glass became the plastic of Rome.

While glass was a popular way to create glazed materials, impurities in the raw materials (and a lack of any way to remove them) meant that glass wasn’t clear. It would be a few more centuries until clear glass could be created – and used in windows. With the ability to create translucent glass, that allowed a significant amount of light to pass through it, a whole new era of possibility was reached for craftsmen.

Techniques continued to develop over the course of the next few hundred years; ‘slab glass’ (molten glass poured onto a flat surface) and ‘crown glass’ (made by bursting a blown bubble of glass, spinning it into a flat disc, and then cutting it to shape), opened up even further possibilities. As time went by, glass started to become widely used in many civilisations.

Glass in buildings

glass building

After glass creation had advanced to such a stage where production was easily achievable, it wasn’t long before people realised its potential for use in building construction – and in particular, windows. While we may automatically associate the term ‘window’ with a glass panel, this is in fact inaccurate: a window is simply a hole in a surface created to allow daylight into a space. Even by the 16th Century, most windows weren’t glazed at all, and would be covered with things like oiled cloth.

As the Tudor dynasty brought with it a period of bountiful prosperity, large glass windows became a way to demonstrate wealth. Designs regularly included a lattice of lead frames which held small, thin glass plates in place, but tastes started to shift during the Italian Renaissance, in which sash windows featuring the previously mentioned ‘crown glass’ were developed.

By the mid 17th Century, glass was being used to construct windows regularly, but was associated with heavy taxation. Between 1745 and 1845, a tax on the number of windows in a property meant that the glazing industry remained exclusively in the remit of the wealthy, and didn’t really take off until the mid 1800s. During this time steps were taken to improve the construction of windows, notably with the rising popularity of sash windows, which started to feature thinner frames.

While for a long time they remained almost exclusively for the wealthy, glass windows had been in use for some time, evidence of which can be found in any number of churches across Britain and Europe. Stained glass – coloured and painted glass pieces held in an intricate lead frame design to form a religious image – were emblematic of the status and wealth of the church for hundreds of years.

Use in modern buildings

glass-building

While steady improvements were made in the way windows and glass were constructed throughout the 17th, 18th, and 19th Century, windows still remained a far cry from the glazing installations we see today. The largest development in the use of glass in modern design was arguably the creation of ‘float glass’, in 1959.

One of the biggest hindrances of glass panels up until this point came from the fact that it was extremely difficult to create a completely flat glass surface. A visit to any building with windows that date back to the 1800s or earlier is enough to see that while the designs of windows improved, the surface of glass panels were determined in large part by the quality of the mold, cast, or craftsman. Float glass changed this.

Between 1953 and 1957, Sir Alastair Pilkington perfected the technique of creating a continuous ribbon of completely flat glass, for the first time. The process involved allowing molten glass to cool on top of a layer of molten tin, as gravity pulled the sheet down at an angle, creating a flawlessly flat panel. This process was a turning point, and float glass is still the primary method by which modern windows are made.

The impacts of this have been huge, and mass production of perfect, uniform glass for the construction market became possible. The technique allowed for the development and rise in popularity of double glazing in the 1970s, and completely redefined modern construction.

With this new possibility, glazing firms have changed from simple construction businesses to pioneers of architectural design, and have been able to focus on innovation – from creating curved glass panels, to designing state of the art glazed atrium roofs.

Cutting-edge and modern glazing

In the modern world, glass isn’t just used for simple windows. Glaziers are still finding new ways to use glass as a raw construction material, as techniques for glass toughening develop. This coupled with all kinds of other innovations mean that the cutting edge of glass technology has become quite something to behold.

Possibly the most significant development in the last few decades has been the evolution of ‘architectural glazing’ – which involves using glass not as a way to enhance a building, but as an integral part of the architecture and design. Incredible glazed constructions, such as London’s now-iconic Shard or the instantly recognisable pyramid in front of the Louvre in Paris, are now viable. It’s particularly exciting that the techniques used to create such structures have become increasingly accessible, and can now be applied to home renovations too.

Other developments have led to glass that is in itself innovative. Glass panels that are imbued with new features, such as heat-resistant glass, switchable glass (panels that can change opacity at the press of a button, via an electric current) and laminated glass that doesn’t shatter when broken have opened the door to a new era of architecture.  

What does this all mean?  

The key takeaway from understanding the development of glass throughout history is that we’ve gone from creating what we can with the materials we have, to a period of glass construction in which what can be achieved is only inhibited by imagination. Glass is no longer simply a tool for letting in light; it’s become a viable tool in the construction of homes, buildings, and other designs.

Possibly the most exciting thing is that this is being tailored to the specific needs and expectations of people living and working today. Offices are being designed with enough glazing to ensure plenty of natural light (which has been found to boost productivity). Homeowners are being offered glass solutions that don’t just look great, but are designed to reduce energy bills and improve insulation. As our lifestyles change, and more people work remotely, glaziers are designing things like glass offices for people’s homes.

As we move into a new age of architectural consciousness, in which emphasis is being placed on wellness design and ‘green’ buildings, glass is at the heart of new developments. From ‘living skyscrapers’ to the first all-glass living environment constructed to study the effects of natural light on sleep, glass has gone from a primitive and difficult-to-use material, to an integral part of the society we’re building.  

 

 

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