The forerunners of modern mirrors were polished pieces of obsidian and bronze discs.  But the Romans began to put metal plates under pieces of colored glass,
which led to a better reflection in them of surrounding objects.
 
  In the 13th century, with the beginning of the production of transparent glass vessels, a glassblower poured tin into the interior of such a vessel, and when it cooled, it smashed the vessel. Later, they learned how to roll glass into flat sheets.
mirror
mirror
 
  In the 16th century, amalgam, an alloy of mercury and tin, was first used for the production of mirrors.  Amalgam-coated mirrors gave a pale reflection.  In their manufacture had to deal with toxic substances.  There have been cases when workers were poisoned to death by mercury fumes.
 
  Therefore, after some time, the amalgam was abandoned.  In the 19th century, the German scientist J. Liebig Invented a harmless, unlike mercury, coating for a mirror.  Instead, they began to put on the glass sheet the thinnest layer of silver.  To prevent the delicate silver film from being damaged, they have learned to coat it with a layer of paint on top of it.  These mirrors gave a very good reflection.

mirror
mirror
 Modern mirror consists of glass and a reflecting layer applied to one side, covered with a protective layer of varnish or paint.  There are several basic manufacturing techniques of mirror cloth.

 1. Aging technology.

 Mirrors are made from ordinary glass.  And at first, blanks of the desired shape are cut out of sheet glass, polished edges and, if necessary, drilled holes.  Then the glass is washed with a special solution so that the surface is absolutely clean.  This is followed by the most difficult stage in production - the deposition of aluminum, less commonly titanium or other metals and alloys.  After spraying, a protective coating is applied.  This method is cheap, but the use of aluminum mirrors is limited by their small size.

 2. More modern technology.

 In the manufacture of silver mirrors, a solution of silver is used as a reflective layer, to which then a protective layer of copper or special bonding chemicals is applied, and only then two layers of protective lacquer coating.  The advantage of this technology is the excellent quality of mirrors and large sizes.  Silver mirrors have increased moisture resistance.