The development of glassmaking technology from small, fragile artefacts to structurally sound glass partitions is an illustration of how rapidly technology can develop with the right breakthrough.
Whilst entire offices and commercial buildings can be built out of different types of exceptionally strong glass with an expectation that even the hardest impacts will not cause them to shatter entirely, the path to get there took centuries.
The path to modern structural glass involves the development of several other technologies, many moments of serendipity, and starts with a moment of history that may, in fact, have never happened.
Vitrum Flexile?
Whilst the use of glass started with the shaping of naturally occurring obsidian during the Stone Age and the first glassmaking was seen in Egypt, the development of glass blowing in the first century BC Syria and its adoption by the newly-formed Roman Empire led to it spreading throughout the early world.
Within a century of the birth of this glassmaking industry, there was a desire for a glass that would not shatter and the potential worth of an unbreakable glass would lead to a story being widely spread of what was known as “vitrum flexile” (flexible glass).
The story, chronicled by Pliny the Elder, tells of an unnamed inventor who travelled to the court of Emperor Tiberius Caesar to showcase a drinking bowl made of a glass that claimed would not break.
After it was stress tested, it had a large dent, but it was not shattered, and the inventor easily fixed the glass back to the way it was with a tiny hammer.
The Emperor asked if anyone other than this inventor knew how to make this glass, and when the inventor responded that he was the only person alive who knew the technique, he was beheaded, allegedly because such a material would be so valuable it would ruin the glassmaking industry.
This story was widely shared at the time and has been retold since the Middle Ages, but whilst it is unlikely to have happened as described, it did plant the seeds for the next two millennia of glass development as people strove to create stronger, better glass technologies.
Droplets Of Curiosity
Whilst no proof of vitrum flexile was ever discovered, there was another discovery that potentially emerged from that era that would begin the development of the making of stronger glass.
Whilst known as Prince Rupert’s Drops due to the person who brought them to Britain and immediately made them a conversation piece for the intelligentsia of the era, the method to make them was believed to date as far back as the Roman Empire.
These tadpole-shaped glass droplets were a point of utter fascination because whilst the slightest touch of the tail would cause them to shatter into almost powder-like shards, the bulbous head could withstand intensely strong forces.
As later experiments would find out, this even included bullets due to the exceptionally unique way in which they were tempered.
Whilst at the time they were largely a thought experiment and were more commonly used as a metaphor than as a potentially practical glass technology, they would ultimately play a role in the development of three glass technologies that would help lead to glass strong enough to step on or use for structural purposes.
Three Approaches To Stronger, Safer Glass
The rediscovery of Prince Rupert’s Drops would have a direct effect on the parallel development of three strengthened glass technologies, each of which would contribute to the modern office as we know it today.
The first and most direct analogue was found in 1874 with the development of a process to create practical tempered glass without the problems found in Rupert’s Drops.
The French inventor Francois Royer de la Bastie would be the first to take the traditional method of creating Rupert’s Drops through the quenching of molten glass and create practical tempered glass as a result.
This is why in some places toughened glass is still known as Bastie glass, although the technique he used was quickly replaced by two other approaches.
Friedrich Siemens of Germany found pressing the glass in cooled moulds created toughened glass that was stronger than what was produced through Mr Bastie’s process. By 1900, a third process developed by Rudolph Seiden was patented in the United States in the 1930s.
This delay, caused in no small part by international tensions, a world war and the growth of tensions that would lead to a second might in some respects explain why two other technologies grew in parallel alongside tempered glass.
The second glass technology was Frank Shuman’s Georgian Wired Glass, often known generically as wire mesh glass. Unlike tempered glass, which is completely clear and requires advanced cameras and instrumentation to see where it gets its strength, wire mesh glass is more straightforward.
Inspired by reinforced concrete, wired glass has a mesh of metal wire that supposedly increases its strength and its ability to resist heat, making it a popular material for fire doors for nearly a century.
Surprisingly, however, wired glass is actually weaker than conventional unwired glass, precisely because the wire mesh creates fault points that can cause it to shatter.
This, along with the wire causing the pieces that do shatter to have a greater risk of causing injury, has led to it being banned in certain countries as a safety material.
The final technology, laminated glass, was discovered largely by accident. Édouard Bénédictus was experimenting with cellulose nitrate, one of his flasks was covered in it and did not break apart when it was dropped. The shattered pieces were held in place by the plastic layer.
This technology would be most commonly seen with car windshields, skylights and structural glazing in areas prone to hurricanes and other major natural disasters.
All of these technologies would lay the groundwork for a rapidly developing world of strengthened glass ideal for a wide range of purposes, which includes entire office buildings that are made out of the material and are a prominent part of the skylines of modern towns and cities.
