Until about 50 B.C. glass objects could only be made slowly due to the limited techniques available. One bottle could take several days to make via casting or cutting techniques. Core-formed objects may have taken 45 minutes to create. Glass furnace technology was such that only small amounts of glass could be made at one time. Because it was difficult and time-consuming to make, glass was a luxury item as rare as gold or precious %%stones%%.
That situation quickly changed with the discovery of glassblowing in about 50 B.C. Romans, probably in Phoenicia (now the region of modern Lebanon), discovered that an object could be formed by gathering molten glass on the end of a pipe and inflating it. The glass could then be shaped into nearly any form with simple tools (watch: Glass Blowing). By about 50 A.D., glassblowers knew how to blow glass into hollow molds to form even more innovative shapes (watch: Mold Blowing).
In addition to the advancement of glassblowing, glassworkers also had the benefit of new glass furnace technology. One known excavated tank furnace could %%melt%% up to 40 tons of glass at one time! Compare this with the size of the glass ingots coming from Egyptian furnaces beforehand, which were only a few pounds.
As with earlier methods of glassmaking in Egypt, Mesopotamia, and Greece, the Roman glassmaker and the glassworker were working in two separate trades. Glassmakers would %%melt%% the glass, allow it to harden and cool in the origination tank, and then break it into chunks to ship to glassworkers. These glassworkers would then remelt the chunks at a lower temperature and fashion glass objects.
For the first time, because of the abundance of material and the new technique of glassblowing, a glassworker could produce dozens of objects per day.
Another advantage the Roman glassblower enjoyed was the potential market of the seemingly endless Roman Empire, including modern-day Europe, North Africa, and the eastern Mediterranean. Blown glass was now quickly made, affordable, and easily attainable.
However, not all glass was common and inexpensive. Luxury glasses were produced throughout the history of Rome’s dominance. Cameo glass is an example of early Roman luxury glass. Glass cameos became popular shortly after the Roman discovery of glassblowing, when glassblowers learned how to encase a glass bubble of one color with one or more layers of contrasting color(s). The resulting "blank" could then be worked by a glasscutter by carving through each succeeding layer(s) to create relief decoration (watch: Cameo Glass). The Morgan Cup at the Corning Museum of Glass (52.1.93) is one of the few pieces of Roman cameo glass to survive fully intact. However, the most famous masterpiece of ancient Roman cameo glass is the Portland Vase, now in the British Museum, which 19th-century glassworkers were challenged to reproduce (92.2.7 and 92.2.16).
Cage cups are examples of late Roman luxury glass. These cups look as if they have been composed of openwork “cages” that have been attached to interior vessel walls. However, the cups are each cut from a single thick-walled piece of glass. The cage and wall elements were not assembled by fusing, since this would leave a visible joint. To make one cage cup, it would take a glasscutter hundreds of hours, thus making these cups luxury items (89.2.22). Cage cups were used for drinking and for lighting. The Museum’s hanging cage cup lamp (87.1.1) would have held olive oil and a burning wick.
The inventions of the blowpipe and tank furnace changed glass history forever by making glass common and affordable. The skill of the glassworkers put Roman luxury glass among the greatest masterpieces in the history of art.