— Ch. 1 · Polished Stone And Bronze —
Mirror.
~7 min read · Ch. 1 of 6
Archaeologists have uncovered polished obsidian mirrors at Çatalhöyük in Anatolia, dating to around 6000 BCE. These early artifacts represent the first manufactured reflective surfaces created by human hands. Before glass existed, people relied on still pools of water or shiny stones to see their reflections. The requirements for a good mirror involve a surface with high flatness and roughness smaller than the wavelength of light. Polished copper mirrors appeared in Mesopotamia from 4000 BCE and in ancient Egypt from 3000 BCE. By the Bronze Age, most cultures used discs made of bronze, copper, silver, or other metals. The people of Kerma in Nubia developed skilled techniques for manufacturing these metal mirrors. Remains of their bronze kilns were found within the temple of Kerma. In China, bronze mirrors were produced as early as 2000 BC by the Qijia culture. Such metal mirrors remained the standard through Greco-Roman Antiquity and into the Middle Ages. During the Roman Empire, servants widely used silver mirrors. Speculum metal, an alloy of copper and tin, served as a highly reflective material until just a couple of centuries ago. These mirrors originated in China and India but were hard to produce. Only wealthy individuals could own mirrors made of speculum metal or precious metals. Common metal mirrors tarnished easily and required frequent polishing. Bronze mirrors suffered from low reflectivity and poor color rendering. Stone mirrors performed even worse in this regard. These defects explain the New Testament reference in 1 Corinthians 13 about seeing darkly in a mirror.
Glass And Silvering Processes
Glass began appearing in mirrors during the 1st century CE with the development of soda-lime glass and glass blowing. Pliny the Elder claimed artisans in Sidon coated glass with lead or gold leaf to create reflective surfaces. The metal provided good reflectivity while the glass offered a smooth surface that protected it from scratches. No archaeological evidence exists for glass mirrors before the third century. Early glass mirrors involved blowing a bubble and cutting off a small circular section measuring 10 to 20 cm in diameter. Their surfaces were either concave or convex, causing imperfections that distorted images. Lead-coated mirrors had to be very thin to prevent cracking from the heat of molten metal. Poor quality, high cost, and small size kept solid-metal mirrors common until the late nineteenth century. Silver-coated metal mirrors emerged in China as early as 500 CE using an amalgam process where mercury boiled away. Glassmakers in France developed flat plates by spinning bubbles rapidly to flatten them. A better method perfected in Venice by the 16th century involved unrolling cylinders onto hot plates. Venetian glassmakers adopted lead glass for its crystal clarity and workability. Fire-gilding techniques produced tin coatings using tin-mercury amalgams evaporated by heating. This caused less thermal shock than older methods. By the 16th century, Venice became a center for mirror production using this technique. These Venetian mirrors reached up to square dimensions and served as luxury decorations. In the late seventeenth century, Countess de Fiesque traded an entire wheat farm for one mirror. The secret leaked through industrial espionage at the end of that century. French workshops succeeded in large-scale industrialization despite mercury vapor toxicity. The invention of the ribbon machine during the Industrial Revolution allowed modern panes to be produced in bulk. German chemist Justus von Liebig invented the silvered-glass mirror in 1835. His wet deposition process deposited metallic silver via chemical reduction of silver nitrate. This adaptation led to mass manufacturing and affordable availability. Contemporary technologies often use electroplating or vacuum deposition methods. John D. Strong used evaporation coating to create aluminum-coated telescope mirrors in the 1930s. The first dielectric mirror appeared in 1937 created by Auwarter using evaporated rhodium.