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The requirements for making a good mirror are a surface with a very high degree of flatness preferably but not necessarily with high reflectivityand a surface roughness smaller than the wavelength of the light. The earliest manufactured mirrors were pieces of polished stone such as obsidiana naturally occurring volcanic glass.
Examples of obsidian mirrors found in Anatolia modern-day Turkey have been dated to around B. Mirrors made of other metal mixtures alloys such as copper and tin speculum metal may have also been produced in China and India. Stone mirrors often had poor reflectivity compared to metals, yet metals scratch or tarnish easily, so they frequently needed polishing.
Depending upon the color, both often yielded reflections with poor color rendering. If well used, however, the mirror can aid moral meditation between man and himself. Socrates, we are told by Diogenesurged young people to look at themselves in mirrors so that, if they were beautiful, they would become worthy of their beauty, and if they were ugly, they would know how to hide their disgrace through learning.
The mirror, a tool by which to " know thyself ," invited man to not mistake himself for God, to avoid pride by knowing his limits, and to improve himself. His was thus not a passive mirror of imitation but an active mirror of transformation.
Because the surface of glass is naturally smooth, it produces reflections with very little blur. In addition, glass is very hard and scratch-resistant.
However, glass by itself has little reflectivity, so people began coating it with metals to increase the reflectivity. Metal-coated glass mirrors are said by the Roman scholar Pliny the Elder to have been invented in Sidon modern-day Lebanon in the first century A.
These circular mirrors were typically small, from five to eight inches cm in diameter. These ancient glass mirrors were very thin, thus very fragile, because the glass needed to be extremely thin to prevent cracking when coated with a hot, molten metal.
Due to the poor quality, high cost, and small size of these ancient glass mirrors, solid metal-mirrors primarily of steel were usually preferred until the late nineteenth century. This was accomplished by coating the mirror with the amalgam, and then heating it until the mercury boiled away, leaving only the silver behind.
This was overcome when people began mixing sodalimestonepotashmanganeseand fern ashes with the glass. There was also no way for the ancients to make flat panes of glass with uniform thicknesses.
The earliest methods for producing glass panes began in France, when people began blowing glass bubbles, and then spinning them rapidly to flatten them out into plates from which pieces could be cut. However, these pieces were still not uniform in thickness, so produced distorted images as well.
A better method was to blow a cylinder of glass, cut off the ends, slice it down the center, and unroll it onto a flat hearth.
This method produced the first mirror-quality glass panes, but it was very difficult and resulted in a lot of breakage. Even windows were primarily made of oiled paper or stained glassuntil the mid-nineteenth century, due to the high cost of making clear, flat panes of glass. The Venetians began using lead glass for its crystal-clarity and its easier workability.
Some time during the early RenaissanceEuropean manufacturers perfected a superior method of coating glass with a tin-mercury amalgam, producing an amorphous coating with better reflectivity than crystalline metals and causing little thermal shock to the glass.Fulfillment by Amazon (FBA) is a service we offer sellers that lets them store their products in Amazon's fulfillment centers, and we directly pack, ship, and provide customer service for these products.
Washtenaw Impressions Table of Contents This list was prepared from an index at the Museum on Main Street. The original index authors are unknown. Beginning in , articles appearing in Impressions are indexed in the Periodical Source Index or alphabetnyc.com with your local library about accessing PERSI through HeritageQuest (currently available at all participating Michigan public.
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