In the fifteenth and early sixteenth century this technique was renewed by Venetian artisans and particularly in the nineteenth century an almost exact imitation of the antique techniques of mosaic glass making was established in Venice, as well as in Bohemia and Silesia. It was the antique Romans, however, who produced this kind of glass for a broader use. In Mesopotamia, the earliest manufacture of mosaic glass was substantiated for the second millennium BC. Mosaic glass, alternatively described as millefiori glass, represents a very special kind of multifariously coloured artistic glass and was used for the creation of exceptional vessels as well as decoration plates for furniture and various architectonical elements. The remaining fragment consisting of a K-pronounced but still Na-bearing glass matrix was most likely produced during the Middle Ages or later. Pb was used as yellow colouring agent, as a flux material and as a stabiliser for the colourant crystals. Mixing of ionic colouring agents and opacifying colourants led to a more differentiated palette of colours. Calcium antimonates, lead antimonate and cuprite are the colourants responsible for white, yellow and red colours, respectively, and additionally serve as opacifiers. Ionic colouring agents are Mn 3+ for violet, Cu 2+ for light blue, Co 2+ for deep blue and Fe 3+ for brown translucent colours. Minor differences in composition are unsystematic, not reflecting the stylistic classification. Eleven of them display a Na-pronounced recipe with low K, Mg and P contents, typical for the Roman period. Twelve representative fragments were studied by electron microprobe analysis and Raman microspectroscopy. About 100 fragments of Roman mosaic and millefiori glass were stylistically attributed to a Hellenistic type, a Ptolemaic and Romano-Egyptian period type and an early imperial period type.

Calcium color materials studio