Tempered Glass

Temper, temper!

By Kirsti Scott 

sea glass windshield glass

Have you ever found a little cube of glass on the beach? It could be from a car window.

When ordinary glass breaks, the resulting glass pieces can be sharp and dangerous. In a car accident, these shards could cut or injure passengers, so the side and back windows of cars are made with tempered glass, which is much sturdier than ordinary glass panes and is designed to break into small pieces when broken. Tempered glass is created by using chemicals to heat and cool the glass, creating equilibrium throughout the glass so when it breaks it breaks uniformly in small pebble-like pieces of glass. Car windows have been made of this “safety glass” since the 1950s.

 

windshield tempered safety sea glass

Though these cute little pebbles of glass are often called “windshield glass,” windshields are actually made with laminated glass, comprised of two pieces of tempered glass with a layer of plastic sandwiched in between. Developed in the 1930s, this type of glass is called “shatterproof” because when it breaks, the shards stay attached to the plastic and don’t fly all over the place. Windshields tend to break in a “spiderweb” pattern that holds together after breaking, thanks to the plastic inside.

 

fold model t with windscreen

 

Windshields were optional on the first Ford Model T Touring car, show in this 1908 ad from Life magazine.

So when you find a tiny glass cube on the beach, softened by years in the waves, be sure to look around to see if you can find any more of the shattered window from a long-lost car.

Photo credits, top to bottom, left to right: Mary T. McCarthy. Mary T. McCarthy, Mary T. McCarthy, Christy Macomber.

This article appeared in the Beachcombing Magazine November/December 2021 issue.

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