MIRROR—

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Mirrors predate glass.

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In the ancient world, reflective surfaces were made from polished stone, obsidian, copper, and bronze. Metal was hammered thin, ground, and burnished until it returned an image. The reflection was dim and required continual polishing as the surface oxidized.

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By the late medieval period, glassmakers on the island of Murano developed methods for producing clear glass backed with metal. Their techniques were closely guarded and protected by the Venetian state. Glass sheets were backed with tin and mercury, creating a brighter and more consistent reflection than polished metal alone.

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These mirrors required skill. Mercury used in the silvering process exposed glassmakers to poisoning over time.

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In the 19th century, chemical silvering replaced mercury amalgam. A thin layer of silver was applied to glass, producing clearer and more stable mirrors. This method remains the basis for modern mirror production.

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A mirror reflects light from a smooth surface. Light strikes and returns at equal angles. The clarity of the image depends on the flatness of the glass and the condition of the metal behind it.

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