Glass production evolved during the Roman Empire with the introduction of glassblowing, which allowed for a great variety of different shapes and styles to be constructed. The technique allowed for easier manipulation of the glass into more intricate designs allowing the vessels to have an assortment of functions. Glassblowing also allowed for a quicker paced production, the hot glass would be blown into a mould and then removed whilst still hot so that the glass maker could still work on it. Roman glass is formed from sand (quartz) which naturally contains alumina and lime. The lime acted as a stabiliser so that the glass was not porous. Sodium Carbonate, in the form of natron, was also added to lower the melting point. The only surplus components then found are additional elements used to colour the glass. Different minerals were added to create a variety of colours; the green colouring seen in this piece would have been intensified by the addition of copper.
To find out more about Roman glass please see our relevant blog post: Ancient Roman Glass and Collecting Roman Glass.