Unguentaria were small perfume or cosmetics bottles made of blown glass. They were extremely popular throughout the Roman Empire, since they contained perfume and oil, considered precious at the time and often used both in private life and public ceremonies. This type of vessels was probably used in funerary and burial rituals, hence their frequent occurrence in archaeological excavations of ancient cemeteries. The iridescence on Roman glass was unintentional, a result of chemical processes after the vessel was buried. Originally, much of Roman glass vessels were modelled in bluish-green translucent colour, which resulted from the iron oxide present in the silica or the sand. However other metal oxides were added to the glass to give it different bright colours; in the case of this beautiful example, cobalt would have been added to the glass to create an intense royal blue colouration.
To discover more about the types and uses of unguentaria, please visit our relevant blog post: Roman Glass: Unguentaria and Cosmetics.