You probably haven’t given much thought to the fact that there’s a slab of chemically strengthened glass in your pocket, deflecting blows from keys or any other hard objects that might scratch against it, or that the hundreds of millions of similar slices of glass lining pockets around the world wasn’t possible not so long ago.
The first huge bump glass got hit in the mid-18th century. It went from being precious and expensive — the stuff of jewellery and fancy shop windows — to being an indispensable material of industry and architecture. An epic, epic unveiling was in order.
When Joseph Paxton’s Crystal Palace was built in London in 1850 for the very first World’s Fair, it was the most massive and arguably most striking building on earth. Constructed from nearly 100,000sqm of glass formed from 293,655 panes, the design used a third of what Britain typically manufactured in a year. It was one hell of an impressive greenhouse.
Thanks to some well-timed tax cuts, which made glass cheaper, and the development of sheet glass, which made glass manufacturing faster, the material was finally able to fill the hole that needed it — and we’re not just talking about windows.
Light. Suddenly, everyone had access to it. And those photons, when allowed in unchanged, were able to do extraordinary things. The same cost and manufacturing leaps that that gave Paxton his glass palace also opened the bricked-up windows of people who previously couldn’t afford the see-through stuff. Trapped light also made way for something else — for the first time in history, people were able to grow plants that didn’t come from their backyard. Seeds schlepped from China, India and North America could now be grown in England with the proper glass cover.
But it also became, um, clear that glass was about more than just its transparency. A large part of why glass is so special is that its atomic structure in its solid form masquerades as a liquid. It resists that repeated structure of crystalline materials, and instead, as liquid glass turns solid, the atoms are frozen into a random arrangement.
It’s also incredibly strong. When glass is free from impurities or scratches, it is much stronger than most metals — like so strong that it can take 2-5 million pounds of pressure per square inch without breaking kind. Sure, that kind of strength is only theoretical, but commercial glass products today still boast an impressive 2000 and 25,000 pounds per square inch before shattering.
When moulded plastic products like auto body parts need a strength booster, they turn to glass, but not the kind that comes in sheets. fibreglass starts as a liquid, just like other manufactured glass products that are awaiting their final shape, but instead of being spread out on plates or blown, the liquid is extruded through hundreds of tiny nozzles. The thin streams of glass are gathered into strands, which can be woven into yarns or made into wool. Because fibreglass is also a top-rate thermal and sound regulator, it’s incorporated into buildings, appliances and plumbing.
And despite the fact that it’s pretty incredible on its own, we’ve figured out how to persuade glass to work even harder for us. Want it to do a better job of standing up to sudden swings in temperature? Dope silica glass — itself very resistant to thermal shock — with titanium oxide and you’ve got a material fit for a deep space telescope. Need something ultra clear? Layering glass with monomolecular coatings will get rid of any underlying reflection, allowing glass to be totally transparent. (Eyeglasses, microscopes, camera lenses — basically anything where it’s super important to limit distortion — benefit from the film). Afraid it might fracture? Etching it with acid, cooling it with air jets or immersing it in a bath of molten alkali salt will do the trick.
Basically, it’s an industrial workhorse — and still precious, just in that we-can’t-live-without-you kind of way.
The Materialist is a regular column about the materials that make up the things we love, want or just plain can’t live without.