Cast Glass Cup
Period: Graeco-Roman, 1st century B.C.-1st century A.D.
Material: Red opaque glass
Dimensions: Height: 4 cm, diameter: 12.5 cm
Formerly Werner Hartmann Collection, Geneva, 1970s.
Complete but reassembled, small repairs, minor chips. Surface largely covered with a light green patina.
This cup, of red opaque glass, was cast and then carved. It is almost hemispherical and supported by a slightly concave, disk-shaped base. The decoration is limited to horizontal lines in low relief and/or incised while the vessel was placed on the turning wheel of the glass craftsman. Concentric circles appear under the base.
In addition to its perfect shape, this vessel is remarkable for the presence of the green/turquoise patina that almost covers the entire surface and gives it its current appearance recalling metal (bronze in particular) rather than glass. This patina, certainly pleasing to the eye of the modern viewer, results from the contact of the soil with the copper contained in the glass; it is nevertheless misleading, because the vessel was originally bright red, as it can still be seen in the upper part of the bowl, near the lip.
Monochromatic opaque glass vessels were very fashionable between the 1st century B.C. and the 1st century A.D. especially. They come in various colors, including white, blue and green mostly, while red is rarer. The small-sized shapes that were used as drinking cups (cups without handles), or to store and carry perfumes (bottles, unguentaria) were the most popular.
Physically, the opacity of the glass is due to the precipitation of crystalline and colloidal components during the cooling process: the presence of these components changes or completely inhibits the light transmission properties of the glass, which becomes more or less transparent. The opacification may be accidental (glass not enough refined, melting temperature too low to remove the microscopic bubbles caught in the mass: it is often the case for the archaic vessels made of glass paste) or induced by the voluntary addition of chemicals components: this process was used by the craftsmen of the late Hellenistic and Roman period, who enriched the vitrifiable compound with substances containing antimony or tin.
Other related vessels made of red opaque glass:
Catalogue of the Constable-Maxwell Collection of Ancient Glass, The Property of Mr and Mrs Andrew Constable-Maxwell, Sotheby’s Park Bernet, 04.06.79, London, 1979, pp. 28-29, nos. 22-23; p. 31, no. 29.
VON SADLER E. et al., Gläser der Antike, Sammlung Erwin Oppenländer, Mainz/Rhine, 1974, pp. 108 ff, no. 287.