Enamel (vitreous alloy) is deposited on the metal surface, using mostly as a basis for copper, less often silver or gold, and fired several times at a temperature from 600 to 900 degrees. Oxides of different metals within the alloy, give different colors. Polychrome, never burning up and not faint colors of enamel caused a persistent interest in this type of artistic creativity. For several centuries, the ways and methods of manufacturing enamel changed and improved: from a simple coating the surface of one color pattern to the polychrome, decorative boxes, painted multi-image compositions, landscapes and portraits. Technique of production gave the names of different types of enamel - cloisonne, notched, painted.

Read more http://artinvestment.ru/news/exhibit...hermitage.html