On the basis of chemical evidence accumulated over the last century, it has been generally assumed that all opaque red glass manufactured prior to the 17th century A.D. was opacified and colored by copper in its metallic or cuprous state. However, a recent study has revealed that red faience manufactured in the second and first mellennia B.C. owes its color to iron free of manganese and copper. Re-examination of published data and new analyses presented here show that between the 15th and 1st centuries B.C. the steady rise in the lead content of red glass was accompanied by a significant increase in iron content. Among recently analyzed fifth century A.D. opaque glasses from Syria and translucent red glasses from Axum, Ethiopia, were red tesserae exhibiting such an excess of iron over copper or containing so little of the latter as to suggest that by the middle of the millennium red glass was being made in a manner analogous to that of red faience; in an oxidizing atmosphere, with iron instead of reduced copper serving as the principal pigment. Contributor note: The instrumentation and techniques used are described in Kaczmarczyk and Hedges, 1983: 10-19 and Lahanier, 1977.