A Short History of Mirrors
In ancient times, obsidian stones were used to make mirrors, as these stones when highly polished were able to reflect with an incredible clarity. As humans evolved, technology did too. Gradually, the properties of metals such as gold, silver and aluminum were used to create mirrors in the similar manner as the obsidian stone. In about 1600 A.D., the silvering process, which is used even today, was discovered and became the most popular way to make mirrors.
The process of making mirrors is simple. It involves coating a glass sheet (which needs to be cut in the requisite shape prior to coating) with silver or aluminum with the help of a chemical process. It is very important that the glass is polished to perfection as any dip, well or impurity left on it would cause waves in the mirror, which would cause distortion of the image reflected.
There are many ways in which the glass is coated with the chosen metal to form a mirror. In high-precision, industrial productions, this is done by bringing the metal to a boil in special chambers and then having it condense on to the glass sheet to form a thin but perfect coating of the metal. For this process to take place, highly specialized machines are needed, such an evaporator and metal boilers, which cannot be installed or used at home. The back of the mirror is painted to protect the metal coating from damage.
The Silvering Process
The process of silvering is simple enough to be duplicated at home without the need of any highly technical or heavy-duty equipment through a series of simple chemical reactions. You need to make two solutions, one that contains silver nitrate, ammonia and distilled water and the other containing Rochelle salts dissolved in the distilled water. When these solutions are mixed, you get the liquid silver in its pure form without having to boil it.
This is the result of chemical reactions between these solutions that isolate the silver while maintaining it in liquid form long enough to be spread on the sheet of glass. This mixture has to be poured over the highly polished glass, during which time it cools down a little and clings on to the surface evenly. The quality of the mirror thus created would heavily depend upon how clean and clear the glass is.
Finalizing the Silvering Process
Though the process of silvering is easy, it will require a little practice before you could get perfect results, as you would need to understand and gauge correctly the temperature and conditions for the solutions to be mixed so the chemical reaction takes place as required. Alternatively, you could always use the ancient process of polishing a thin slab of obsidian stone or metal (silver, aluminum, copper or gold) to create a very unusual handcrafted mirror.
Originally found on: http://www.ehow.com/how-does_4569519_how-mirrors-made.html