Have you ever driven in a car with a small crack in its windshield (or windscreen, if you will)? Chances are, you have. At the very least, you’ve been in a car when a small rock hit the window – no doubt startling the driver, but otherwise leaving everyone without any injuries. The reason for this is safety glass (specifically, laminated glass) – without this technology even a small crack could prove devastating for a vehicle traveling at high speeds.
Of course, there are other applications, such as skylight windows, glass doors, storefronts et cetera – in other words, any glass with which people interact regularly. In this case, safety refers to the glass breaking down safely. It won’t stop a bullet, but, when breaking due to impact or pressure, the laminated glass pane will not break into dangerous shards, capable of seriously maiming someone. Instead, it’s held together by an elastic coating. The concept is simple enough – but it didn’t appear until early 20th century.
The person credited with the discovery is French chemist Edouard Benedictus. One day in 1903 Benedictus happened to drop a flask on the floor – you know, these things happen. To the scientist’s surprise, the flask didn’t shatter – but not because it withstood the impact. It broke, but its pieces were still held together. After further inspection, Benedictus noted that the glass flask was coated with plastic cellulose nitrate – the vessel contained the solution which evaporated, leaving only a thin film on the inside. He realized that this could be the solution to the growing traffic safety problem.
At the time, the automotive industry did not really prioritize safety – driver or pedestrian – when it came to accidents. To give you an idea of how bad it was, here’s an excerpt from the book The American Automobile Industry and the Development of Automotive Safety, 1900-1966, by Joel W. Eastman:
"Early windshields sometimes fractured as a result of the normal stresses of operating an automobile on the highway, and a minor collision or a rock thrown up by a passing vehicle could completely shatter a windshield, sending a shower of razor-edged pieces of glass flying through the interior of the motorcar. A front-end collision in which the driver and passengers were thrown forward into the windshield could prove even more hazardous, and when the first fully enclosed body styles were introduced — featuring glass windows on all four sides--many people were, at first, understandably hesitant about purchasing and riding in them."
Benedictus used his accident to develop laminated glass for car windshields in 1911. However, his solution was deemed too expensive for mass production. The technology, however, was found useful – gas masks used during WWI had laminated eyepieces, and eventually safety concerns outweighed costs. Joel Eastman continues:
"Henry Ford, in his characteristic way, brushed aside considerations of cost and production difficulties, and ordered that the new glass be installed in the windshields of all the new models. Thus, when the Model A 179 initially appeared in late 1927, it was not just the only car in the low or medium priced class with the new windshield, but one of the few cars of any price in which it was available."
Soon enough the feature became a staple among car manufacturers, and while the technology has improved, the core principle remains the same – layers of glass and a special coating which effectively saves thousands, if not millions, from injuries, or worse.
