Published: May 15, 2018 By

Catalogue Entry Photograph of a dark glass bowl, from a slightly raised angle against a neutral gray background.

From the Catalogue of Ancient Glass in the University of Colorado Museum

Gift of H. Medill Sarkisian and Justine Sarkisian Rodriguez (1979)
Transferred to CU Art Museum (2008)
Height: 3.8 cm
Diameter (max.): 10.2 cm
Roman, 1st century C.E.

Classification: Isings Form 3a; Harden Fabric 2 or 3

Description: Unworked lip on shallow bowl with somewhat sagged profile. 21 pillar-molded ribs descend from pronounced shoulder to flat base of vessel. Much iridescence and flaking, to the extent that the original color is not discernable (at present it is several shades of brown). Sagged (i.e., heated on a dome-shaped mold).

Comment: The weathering of this bowl has been extensive and it has been abused in other ways, as indicated by a patch of glue-like substance on side. Nevertheless, the shape and what remains of the original coloring suggests this bowl may be mosaic (cf. Eisen 1927, pl. 32; von Saldern 1968, no. 12). Other examples of this shape are Hayes 1975, no. 50 and Grose 1989, no. 232.


The shape of this bowl was not determined by free-blowing, mold-blowing, or core-forming. It was made through a process called "sagging" or "slumping". This shaping technique involves taking a flat disk or sheet of pliable glass and placing it on top of a solid mold to form the shape and design on the interior of the vessel. Then the glass is worked as it lays "slumped" or "sagged" over the dome-shaped mold to create a design on the exterior of the vessel. This process means that this bowl was worked while upside down (1). 

This bowl may have been made of mosaic glass, which is made from many small pieces of glass fused together in a kiln. The glass bits are laid side by side in a disk shape on a paddle, which is slid into a hot kiln. When the disk comes out of the kiln hot and pliable, the glass is all pressed together to form one circular sheet of glass. Then the flat glass is sagged to the bowl mold (2).


  1. Robert J. Charleston, Masterpieces of Glass: A World History from the Corning Museum of Glass (New York: Harry N. Abrams, Inc., 1980): 39-40.
  2. Hugh Tait, ed. Five Thousand Years of Glass (Philadelphia: University of Pennsylvania Press, 1991): 218-221.


  • Eisen, G. A. Glass: Its Origin, History, Chronology, Technic and Classification to the Sixteenth Century, v. 1. New York: W. E. Rudge, 1927.
  • Grose, D. F. Early Ancient Glass: Core-Formed, Rod-Formed, and Cast Vessels and Objects from the Late Bronze Age to the Early Roman Empire, 1600 B.C. to A.D. 50. New York: Hudson Hills Press, 1989.
  • Hayes, J. W. Roman and Pre-Roman Glass in the Royal Ontario Museum. Toronto: 1975.
  • von Saldern, A. Ancient Glass in the Museum of Fine Arts Boston. Greenwich, CT: New York Graphic Society, 1968.