The earliest man-made mirrors were of polished stone, some of which have been found in Turkey and date back at least 6000 years (https://www.mirrorhistory.com). Ancient Egyptians used a sheet of polished copper as a mirror. Back-surface mirrors made of metal-backed glass were first produced in Lebanon in the first century AD. Justus von Liebig, German chemist, produced the silver-coated glass mirror in 1835 through the deposition of a thin layer of silver by the chemical reduction of silver nitrate. This technique made the mass production of mirrors possible.