The story of the mirror does not begin with the advent of the modern silvered mirror. Other materials, such as copper, bronze, tin, mercury, and gold leaf, have been used in mirror-making since antiquity and before. Glass-metal mirrors, or mirrors consisting of a pane of glass with a thin sheet of polished metal behind it, have been known since antiquity, but owing to imperfections in both the glass (clear glass was difficult to make reliably until the 16th century) and the metal, they weren't widespread, but they did exist.

In the middle ages, glass was expensive and probably not within the reach of a peasant's budget, especially not for something as trivial as a mirror, so glass-and-metal mirrors would not have been accessible. However, any polished metal can be used as a crude mirror. Even without polished metal, though, peasants would be able to see their reflections in puddles of water, rivers and lakes, so commoners would certainly know what they looked like.

The proliferation of the mirror as a household item depended on several factors. The two biggest were the development of a cheap, mass-production-friendly process for silvering glass (essentially laying down a thin, even, uniform coat of silver amalgam on the back-side of a pane of glass) by Liebig in 1835, and the dramatic drop in glass prices during the Industrial Revolution in the 19th century. Prior to that, it was still possible to make glass-metal mirrors, but they were extremely pricey, generally small, and reserved for the rich. Mirrors proliferated among the wealthy classes in the 17th and 18th centuries, after glass technology became advanced enough to reliably produce clear glass in uniform panes. The metallizing processes used for the backings of these mirrors were less-advanced and much more expensive than Liebig's process, however.

As a bit of an aside, the development of glass-making technique in Europe to the point where thin, uniform panes of crystal-clear glass suitable for mirrors could be mass-produced is a really fascinating, under-emphasized part of the Renaissance and following period up to the Industrial Revolution and beyond. Astronomy, for one, depended on glass of sufficient clarity and quality, ground into precisely the right shape to form lenses for telescopes. Navigation also relied heavily on telescopes, so the age of exploration in relied heavily on innovations in glass-making technology. Considering how much wealth poured into Europe with Colonialism, and Colonialism's contributions to the accumulation of capital that led to the Industrial Revolution, the modern world owes a lot to glass.