The industry was divided into two categories: glass听尘补办颈苍驳听and glass听working (1).听 workshops, which have been found through the Roman Empire, as well as in the city of Rome itself, were usually situated near places where the raw materials were available. The materials needed to make glass include sand, nitrate, and lots of heat. To fuse the ingredients together, a kiln must be heated up to a temperature of 1100 degrees Fahrenheit. This was accomplished with large amounts of wood for burning听and a strong breeze to provide enough oxygen for the fire (2).
Early on, glassmakers knew with the addition of metallic oxides and the 听depended upon the qualities and quantities of added materials. Popular for glass were various shades of blue, created by adding cobalt oxide and copper oxide. A small amount of iron caused glass to turn green, while manganese could have created yellowish or purple glass. If a glassmaker desired colorless glass, she or he could add a neutralizing agent (3).
Melted together, the ingredients听created molten glass. This substance, too liquid to work with, would be cooled until it hardened into a solid (4). The raw, unshaped glass chunks would be given to glassworkers in separate workshops. The glassworkers would need to remelt the glass in order to make it pliable enough for shaping. A kiln only needed to reach 750 degrees Fahrenheit in order to heat glass enough for it听to become workable听and that temperature could be accomplished in a simple shielded hearth or (5).听
Once the glass was plastic enough for working, there were a few methods available for shaping or working glass vessels. Among the earliest methods in Italy produced听听through a laborious and time-consuming process. Other methods were quicker and more cost-effective, including听,听,听, and听.听
Objects in the University of Colorado Museum's collection of Roman glass include representatives of several different听kinds of glass manufacture. A 6th to 4th century B.C.E. amphoriskos, for example, was core-formed and a 1st century C.E. pillar-molded bowl was sagged or slumped. A 1st century C.E. flask (pictured at right) was free-blown and a 1st century B.C.E. or 1st century C.E. ribbed cup was mold-blown.
Footnotes
- "It is important to realize that there is a distinct difference between the knowledge of how to make glass and how to work it." Quote from Robert J. Charleston,听Masterpieces of Glass: A world history from the Corning Museum of Glass听(New York: Harry N. Abrams, Inc. 1980): 12.
- Stuart J. Fleming,听Roman Glass: Reflections of Everyday Life听(Pennsylvania: University of Pennsylvania Museum, 1997): 10-11.
- Donald B. Harden,听Roman Glass from Karanis听(Ann Arbor: University of Michigan Press, 1936): 6-9.
- E. Marianne Stern,听Roman Mold-Blown Glass听(Toledo, Ohio: Toledo Museum of Art, 1995): 42.
- Fleming 1997: 10-11.