All elements with 2 or more isotopes show natural variation in their isotopic composition as a rseult of isotope fractionation during physical processes and/or (bio)chemical reactions. Determination of the isotopic composition of an element in ancient glass and comparison to those in raw materials possibly used in its manufacturing can provide information on the provenance of the effectively used raw material. Cu can be present in glass as a colorant, Sb as a decolorzer and Ti as a result of Ti contamination of the sand used. The isotopic analysis of these elements in the context described is envisaged.