On Cobalt in the Old Russian Lead Glass

Abstract

The objective of this work is to consider all now known cases of cobalt usage in the Old Russian lead glass and to estimate the availability of cobalt blue in the pre-Mongolian time. In the Old Russian glassmaking, beginning in XI cen. AD and based on the production of lead glass, the use of cobalt was very rare. Until recently only three assured cases of cobalt using for blue coloration of bracelets and beads were described. In addition, two cases of probable cobalt coloration also published, but owing to weakness of reliable analytical methods at that time, the use of cobalt was not confirmed. Seven more another glass artifacts containing cobalt were obtained during the last twenty years by the author. All these bracelets and beads of potash-lead glass have been excavated in Old Russian towns and cities such as Novgorod, Vladimir, Smolensk, Tver, Suzdal etc. and occurred in the strata of pre-Mongolian time XI-XIII cen. One more blue bracelet of this type is originated from Bolgar, the city of medieval Volga Bulgaria, and analyzed in Kazan University taken into account also. The single early Russian artifact, taking place from St. Sophia Cathedral in Kiev, could be considered as product of Russian workshop only with high portion of doubt. As opposed to all other analyzed artifacts it is a piece of tessera from one of the earliest Russian temples, and has an extremely high content of cobalt, enhanced content of sodium and contains antimony, acting as opacifier. In Russian lead glass antimony is used rarely and is detected only for one other considered here sample else. In two artifacts, one of which with enhanced manganese content, the blue coloration has not been achieved with cobalt blue using, These facts confirm the opinion that cobalt blue was imported in Russia on occasion from different sources and tradition of its usage in the pre-Mongolian time has not obtain own development.