Metal mirrors have existed for millennia, evolved from their older polished-stone predecessors. Metal mirrors first emerged around 6000 years ago in Ancient Mesopotamia and Ancient Egypt and have since been fashioned from a huge range of different metals. Some have been chosen for purely practical purposes, some for aesthetics, and some for their specific properties. From the earliest mirrors made from whatever reflective materials were available to the specific metal mirrors we construct today for use in specialised functions, here we’ll break down the various metals used in mirrors over the ages and take a closer look at their features.
Copper and bronze were some of the earliest metals to be made into smooth surfaces and polished for a reflective effect. Popular across Ancient Egypt and Mesopotamia, these metals are more malleable than cast iron and are able to be polished to a bright finish. However due to their colour they are much more effective at reflecting the red spectrum of light and will not return a true colour reflection like more modern silver mirrors do.
Aluminium and beryllium are two commonly-used metals for silver mirrors today. Aluminium is often used as a thin coating for standard glass mirrors while beryllium is used in things like cameras and telescopes due to its light weight and is common in space and military applications. Aluminium can also be used in moving mirrors as it is easy to sculpt into specific, complex shapes.
Rhodium and chromium are both specialized metals used for specific purposes. Rhodium is used for its durability, even though it is less reflective than silver and aluminium. Rhodium is commonly used in dental mirrors, which is why the more robust metal is preferred! Chromium has similar properties but is highly toxic, so it couldn’t be used in medical or dental settings. Instead, chromium is usually found on vehicle mirrors, the wings and the rear-view.
Like aluminium, silver is often used in standard mirrors, but it suffers from a dip in reflectivity around the ultra-violet end of the light spectrum, so it cannot be used for space telescopes and other machines of this nature. Like copper and bronze, gold doesn’t return a colour-true reflection, and so is rarely used in regular mirrors. Gold is used in applications with polarised lasers as it does not disrupt the polarization, due to its reflectivity at any angle, it is also used commonly in scanners.