Introduction

The term ‘vitreous’ literally means a material with a glassy state. Thus a consideration of the full range of ancient vitreous materials should include faience, Egyptian blue, glazed steatite, glass, glaze, and enamel. A vitreous layer may have been formed adventitiously in a high-temperature environment in which plant ash and silica combined, such as during metal smelting. However, this is not considered here. The chronological sequence in which vitreous materials appeared was the following: the earliest faience appeared c. 4500 BC at about the same time as glazed steatite. The first glass appears to have been made c. 2500 BC and the first glazed pottery and enameled metal some 1000 years later. The first appearance of all of these vitreous materials seems to have occurred in the Middle East or in an adjacent area. Since the bulk of ancient vitreous materials are glass and pottery glazes, most discussion here will be focused on these categories.

Faience, a material consisting of a core of silica held together with a vitreous phase, has much in common with the earliest glass. Both materials were produced with silica, plant ash, and a colorant. However, the earliest glass was formed by a complete fusion of plant ash and silica so that there are no discernible separate phases. Colorants were added to produce one of the more distinctive visual characteristics of vitreous materials. Initially, low-level glass production occurred for the production of decorative trinkets like beads; 1000 years later (by 1500 BC) the first (core-formed) vessels were made as part of an elite production sphere associated with Bronze Age Royal palaces. The description of glass production in cuneiform texts indicates that ritual played an important part. Hellenistic cast glass vessels were mass produced, and soon after glass-blowing was invented (c. 50 BC) mass-produced glass vessels become available to many more people in the Roman world. The first sets of mold-blown glass vessels were produced. Glass windows were first made in the first century AD, with arguably the largest-scale production in the high medieval period in the West. The period saw an increase in the volume of trade in finished vessels and scrap glass (cullet). In China, jade was used instead of glass in many contexts. Nevertheless, there is evidence for innovation in Chinese glass production from c. 800 BC with diagnostically different raw materials being used from those in the West. In the Far East, glazed pottery production reached a high level of sophistication well before this occurred in the West (Figures 1 and 2) (see Ceramics and Pottery).