"Oh, think about how nice it would be if we could go through the mirror! I'm sure there are some beautiful things inside! Let's make sure there's a way to go through it, let's have it all become like a light veil of fog ... but look ... it's transformed! It will be easy to pass now! "
Lewis Carroll in Alice in Wonderland
The first methods to observe one's own image undoubtedly exploited water. Rivers, lakes, puddles offered a blurred reflection of their face. Subsequently, with the discovery of metals and their reflecting characteristics, Etruscans, Egyptians and Greeks preferred the use of primordial mirrors, which consisted mainly of polished and decorated bronze plates.
For those who know the French advice, consult the page of the Louvre museum in Paris that describes the mirror on the side. In the meantime, the blackening of the bottom of glass sheets began, using lead. This made the mirrored glass surface. The Romans started small productions, but without great results.
In the 12th century, in Germany and in Lorraine, glass was begun to be metallised with lead and tin, but it did not arrive at the production of large mirrors. In 1540 Vincenzo Redor, a Venetian, refined a process of leveling the glass slabs that laid the foundations for a production of mirrors of the highest quality, known as Venetian mirrors and soon known throughout the world.
The working process foresaw that sheets of tin were pressed onto the glass surface thanks to a mercury bath. Moreover, the frames were very accurate and varied: covered with strips of cut mirror, leaves and glass flowers. For this reason the Venetian mirrors were very valuable and destined to decidedly affluent classes.
The silvering process, introduced in the second half of the nineteenth century, made the production of mirrors less expensive and the same as we know it today.
(from "Reflections on mirrors in art" by Roberta Lapucci, from the book "Titian in Milan: Woman in the Mirror", edited by Titian, Valeria Merlini, Daniela Storti, Skira, 2010)