Roman Glass
Read this article about the history and evolution of Roman glass production. The manufacture of glassware was known throughout the ancient world, but Roman artisans produced glass on an unprecedented scale. During the first century BCE, the invention of glassblowing allowed artisans to quickly create glass products in a wide range of shapes, bringing cheap glass to mass markets.
Production
Composition
Roman glass production relied on the application of heat to fuse two primary ingredients: silica and soda. Technical studies of archaeological glasses divide the ingredients of glass as formers, fluxes, stabilisers, as well as possible opacifiers or colourants.
- Former: The major component of the glass is silica, which during the Roman period was sand (quartz), which contains some alumina (typically 2.5%) and nearly 8% lime. Alumina contents vary, peaking around 3% in glasses from the western Empire, and remaining notably lower in glasses from the Middle East.
- Flux: This ingredient was used to lower the melting point of the silica to form glass. Analysis of Roman glass has shown that soda (sodium carbonate) was used exclusively in glass production. During this period, the primary source of soda was natron, a naturally occurring salt found in dry lake beds. The main source of natron during the Roman period was Wadi El Natrun, Egypt, although there may have been a source in Italy.
- Stabiliser: Glasses formed of silica and soda are naturally soluble, and require the addition of a stabiliser such as lime or magnesia. Lime was the primary stabiliser in use during the Roman period, entering the glass through calcareous particles in the beach sand, rather than as a separate component.
Roman glass has also been shown to contain around 1% to 2% chlorine, in contrast to later glasses. This is thought to have originated either in the addition of salt (NaCl) to reduce the melting temperature and viscosity of the glass, or as a contaminant in the natron.