Mirror
Mirrors are objects with reflective surfaces.
History[edit | edit source]
The earliest manufactured mirrors were produced by polishing stone such as obsidian, a volcanic glass. Obsidian's high melting point would prevent prehistoric people from reshaping these mirrors so they would likely be small. Obsidian is also brittle so these mirrors would be fragile.
In the Bronze Age, mirrors started being produced by polishing pieces of copper, tin, silver, or other metals. Metals are more durable than stone and can more easily be reshaped, but tarnish with exposure to air and would need to be polished again over time.
In the Middle Ages, mirrors started being produced by depositing tin onto sheets of glass. The glass would be used as the front surface of the mirror to protect the metal and prevent tarnishing. Mercury vapor was often used to deposit the tin, making this process hazardous to workers.
In the Industrial Revolution, mirrors started being produced by reducing a solution of silver nitrate in water onto sheets of glass (used in Tollen's test). This remains the most widely used method of mirror production as the amount of silver required is very low, keeping costs reasonable.
Since 1920, mirrors for optical and scientific purposes have been made by sputtering metals such as aluminum directly onto glass. This is more expensive than the wet silver deposition process so is not found in standard mirrors.
Fire Starting[edit | edit source]
Concave mirrors such as parabolic mirrors can be used to focus sunlight and ignite carbon-containing materials.
Dependencies[edit | edit source]
References[edit | edit source]
| This article uses material from the Wikipedia article mirror, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors). | 
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