invented by 16th-century Venetian glassmakers on the island of Murano, the method of making mirrors out of plate glass was to have a profound influence on the role of the fireplace. Full-length mirrors sitting above the marble fireplaces served to emphasize the importance of the fire. The fire itself was also a source of light and the mirror with candle sconces on either side brought considerable light to the rooms.For over 100 hundred years Venice retained its monopoly of the secret of the mercury process used to produce these mirrors and Venetian mirrors decorated the palaces of Europe. As with all things, industrial espionage resulted in the secret of the process arriving in the workshops of Paris and London. The French, in particular, succeeded in developing a large scale process that ultimately resulted in mirrors being affordable by the masses. The toxicity of the mercury used in the process remained a considerable problem.