Reflections Through Time: The Evolution of Mirror-Making

-Karthik Gurumurthy

Ever wondered how mirrors are actually made? It’s got a pretty fascinating history!

People have been obsessed with checking themselves out forever – whether from vanity, curiosity, or who knows what else. The Egyptians were already making mirrors around 2500 BC, using super polished bronze, silver, or even gold.

But glass mirrors? Those didn’t come around until much later. The first commercial ones were created in Venice back in 1564. They made them by flattening blown glass and coating the back with this weird mixture of mercury and tin. The Venetians basically cornered the European mirror market for centuries after that!

The modern method we use today didn’t show up until 1840, when this German chemist named Justus Liebig figured out a new technique. He used silver-ammonia compounds and mixed them with reducing agents like invert sugar, Rochelle salt, or formaldehyde. This process deposits metallic silver evenly across the back of a smooth glass pane.

What’s funny is that regular mirrors actually create multiple reflections – you get a slight reflection from the front glass surface plus the stronger reflection from the silvered back. You don’t really notice this in everyday use, but for scientific equipment like telescopes, that tiny distortion from light passing through glass is a major problem.

That’s why telescope mirrors are coated differently – they’re silvered on both the front AND back. These days, they don’t even use silver anymore since it tarnishes too easily. Instead, they use aluminum or an aluminum-chromium mix.

The process for making these high-tech mirrors is super cool – they use vacuum deposition, where they heat metal on a coil inside a vacuum chamber. The metal vaporizes and deposits an incredibly thin film (we’re talking millionths of an inch) onto specially shaped glass. Science mirrors make your bathroom mirror look pretty basic by comparison!