Ancient glass-making stretches from the mid-2nd Millennium BC in Mesopotamia, and was quickly prominent in Egypt. Due to the costliness of early techniques, glass was considered a luxury product and reserved for use by the elites: King Tutankhamun’s gold mask was inlaid was a variety of colourful glass beads. The invention of glass-blowing in the mid-1st Century BC revolutionised the industry. In the Roman period, glass became an affordable and essential household commodity, and experimentation in colour, size and style exploded. The delicate ribbing seen on this piece would have been achieved by blowing the glass into a specialised mould.
Made up from a majority of silica, different coloured glass can be achieved through the addition of metal and minerals. For instance, cobalt-based compounds yield blue glass; copper alloys yield green glass; calcium antimonate produces an opaque white colour, and lead antimonate gives an opaque yellow colour. The most commonly found blue-green hue is a result of the presence of iron oxide impurities in the sand used in the production of natural Roman glass. The exquisite iridescence on archaeological glass is a result of the chemical weathering of its surface by slightly acidic water presented in the soil in which it is buried. This serendipitous embellishment attests to the life story of the object.
To find out more about Roman glass, please see our relevant blog posts: Ancient Glass and Collecting Ancient Glass
