Our lack of knowledge of glassmaking technology during the transition between the Bronze and Iron Ages lies partly in the small amount of well-excavated glass artifacts. One site that has produced a range of suitable material is Hasanlu in northwestern Iran, excavated by Robert H. Dyson, Jr., from the University of Pennsylvania. Glass, glaze and faience were analyzed using electron microprobe, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and laser fusionoxygen isotope analysis. The results show that the glasses from Hasanlu were made using different combinations of quartz sand, alkali feldspar, dolomite, copper ore, copper alloy metal, copper refining slag, antimony ore, and lead ore. The oxygen isotope analyses indicate that more than one geological source of quartz was used to make the glasses. The range in major element compositions and oxygen isotope ratios are large and suggest that the glasses were made in more than one factory. The raw materials and procedures identified for the manufacture of the Hasanlu glasses indicate that glassmakers understood the interaction of materials they used. Many of the glasses from Hasanlu are different in major element composition from those of other 2nd millennium BC and early 1st millennium BC glasses. These differences suggest that the glasses from Hasanlu were made either near Hasanlu or imported into Hasanlu from an as yet unidentified region. The comparison indicate that at least in the early 1st millennium BC, the knowledge of glassmaking probably extended well beyond the boundaries of Mesopotamia and Egypt.