Enamel is a hard and timeless material. The colors are preserved in a uniqe way.
At Louvren in Paris you will find Enamel works from the Byzantine Empire 

During the Predynastic period of Egypt 4210-2680 BC , pottery was made by casting lumps of clay in the required shape and then left out in the sun to bake. At the time of the period 2680 BC in the Old Kingdom, the turntable had been invented, so ceramics became more symmetrical in shape and were often covered with enamel.

The enamel used is largely composed in the same way as glass, quartz, soda ash, feldspar, fluorspar, etc., which are mixed and melted. The melt is then rolled between water-cooled rolls so that thin flakes are formed. These are generally called frits and form the base of the enamel itself. The colors or color bodies consist of metal oxides, these are mixed and ground with the frit in ball mills to the right consistency. The color is then set with sodium nitrite or sodium aluminate. You can say that it is a glass mass that can be colored with white, black or colored metal oxides. The enamel artist's canvas is a steel plate 1.5 - 2 mm thick and after coloring the plates with the glass mass I burn them to 820 grades.