Published: May 15, 2018 By

Catalogue Entry Photograph of a clear glass bowl with a slightly flaring lip, from the side 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: 7.1 cm
Diameter (max.): 9.4 cm
Eastern Mediterranean, 1st century B.C.E. to 1st century C.E.

Description: Everted rim with unworked edge turning in at top. Slight shoulder. Body bulges out in center. Pinched-out ribs extening from just above middle of body to underside of base. Flat bottom. Pale greenish tint. Some iridescence and a great deal of white incrustation. Mold-blown.

Comment: This type of vessel, sometimes known as a zarte Rippenschale, bears some resemblance to Isings Form 17, but without marvered threads. Decorated versions of this type (e.g. Eisen 1927, pl. 37; Megaw 1957, pl. 4f; von Saldern 1980, pl. 2) have similar bodies. Other, simpler examples are Fitzwilliam Museum 1978, nos. 60a and b; Gill 2000, p. 102; and also Avigad 1983, fig. 219, a fragment of a bowl from Jerusalem dating to the early 1st century B.C.E. (or earlier). See, also, Weinberg and Stern 2009 G 213. 


Ribbed bowls belong to Grose's Group C (1). These bowls are differentiated from ther grooved and fluted bowls in Grose's Groups A and B by the flat or slightly concave bottom. Their self-supporting nature meant that they could serve as either luxury or daily use tablewares, while the ribbed sides provided a solid grip. The ribs were likely formed by pinching the glass with a tool while it is still soft enough to shape. Vertical ribs are very common on Roman glass, as it is a simple decorative technique that is quickly and easily accomplished (2). 

Ribbed bowls originated in the Eastern Mediterranean, but they soon spread throughout western Europe in ways that other bowl types did not and they were standard in the entire Roman Empire from the 1st century B.C.E. to the late 1st century C.E. (3).

The pale green tint of this glass bowl comes from a small amount of natural metal in the ingredients. All sand used for making glass has a very small percentage of metals in it. Green glass is caused by one to three percent of iron mixed in with the sand. It is uncertain how much the ancient Roman glassmakers could control the tint of the glass, but they knew which metals caused which colors (4). During the height of the Roman Empire, colorless glass became more and more desirable. The less tinted the glass was with color, the more expensive it was (5).

This bowl was not free-blown or core-formed; it was shaped using a mold, either through by a process called mold-blowing or perhaps by sagging or slumping. Mold-blowing was invented around 25 C.E. (6). Hot, pliable glass is gathered at the end of a pipe by the glass-blower, while another person closes a two-piece mold around the glass that is stuck to the pipe. Then the glass is inflated while trapped within the hollow mold, so that it takes on the pre-determined design and shape. Once the glass has cooled and hardened, the mold is opened up to reveal the finished bowl or bottle. Sagging, on the other hand, involved sagging or slumping a disk of softened glass over a mold. Molds could be made out of fired clay, plaster, wood, or stone. They were very convenient because they were reusable: a glass-blower could produce many glass bowls all with the same shape and design from a single mold. Many Roman glass vases have vertical marks from where the two halves of the mold met (7). 


  1. Gladys D. Weinberg and E. Marianne Stern, Vessel GlassThe Athenian Agora XXXIV (Princeton: The American School of Classical Studies, 2007): 33.
  2. E. Marianne Stern, Roman, Byzantine, and Early Medieval Glass (New York: Hatje Cantz Publishers, 2001): 47.
  3. Weinberg and Stern (2007): 33.
  4. Donald B. Harden, Roman Glass from Karanis (Ann Arbor: University of Michigan Press, 1936): 6-9.
  5. Hugh Tait, ed., Five Thousand Years of Glass (Philadelphia: University of Pennsylvania Press, 1991): 79-82.
  6. Tait 1991: 62.
  7. Stern 2001: 45-48.


  • Avigad, N. Discovering Jerusalem. Nashville: T. Nelson, 1983.
  • Eisen, G. A. Glass: Its Origin, History, Chronology, Technic and Classification to the Sixteenth Century, v. 1. New York: W. E. Rudge, 1927.
  • Gill, D. W.. “Communications and Trade,” in The Atlas of World Archaeology, ed. P. G. Bahn. London: Greenwich Editions, 2000: pp. 102-103.
  • 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.
  • Glass at the Fitzwilliam Museum. Cambridge: Cambridge University Press, 1978.
  • Megaw, A. H. S. “Archaeology in Cyprus,” Archaeological Reports 4 (1957): 43-50. 
  • Weinberg, G. D. and E. M. Stern. Vessel Glass. The Athenian Agora Vol. 34 (Princeton: The American School of Classical Studies at Athens 2009). 
  • von Saldern, A. Ancient and Byzantine Glass from Sardis. Cambridge, MA: Harvard University Press, 1980.