The Iulia Felix (also spelled Julia Felix) is the name of a small Roman cargo ship wrecked in the Adriatic Sea six miles off the coast of the town of Grado during the last part of the 2nd century or first half of the 3rd century AD. The ship is a well-preserved 'corbita', a merchant ship used by the Roman Empire intended for long distance trading voyages. The Iulia Felix measured between about 15 and 18 meters (50-60 feet) long and 5-6 m (16-20 ft) wide.

Archaeological investigations of the wreck have discovered that about 560 amphorae--storage jars--were within the cargo hold when she went down, containing a variety of oils and spices. Some bronze artifacts were recovered, including the sculpted bronze heads of Greek god Poseidon and the Roman goddess Minerva. Those artifacts date the wreck to the first half of the 3rd century AD. But the most interesting element in the cargo hold, from an archaeological standpoint, was glass.

Iulia Felix and Glass

In the cargo hold of the Iulia Felix was discovered a large wooden barrel, about 1.4 m (4.5 ft) high, filled with nearly 11,000 broken glass vessel fragments, from a wide variety of cups, small jars, trays, goblets, bottles, and plates. It is apparent that the glassware was broken before the ship went down: the glass fragments are believed to have been intended for glass works, perhaps those on the Venetian island of Torcello where they would have been recycled into new glass vessels.

The ability to recycle broken glass--cullet is the glassmakers' term for broken glass intended to be recycled into new glass--was a revolution in the glass industry: and like all innovations it drove a new technology.

The earliest glasses were intensely colored blue-greens and dark yellows and were very attractive: but recycling the broken pieces of mixed colors created an indistinct, downright ugly muddy color.

The most common colors recovered from the Iulia Felix barrel were pale blue-green (6000 sherds, weighing more than 100 kilograms [220 pounds]); clear (about 3000 sherds), and then green. The pale and colorless glasses could be safely recycled. Pale blue and green were the result of iron impurities in the raw materials. Colorless glass was extremely thin, and required expensive decoloring processes to make--the emperor Diocletian set prices for raw glass at the time, ranging from 13 denarii for colored, and 24 for colorless glasses.

Trade Networks

Chemical analysis of the colored glass sherds identified a wide variety of compositions, suggesting that they were made in several different locations throughout the Mediterranean. That suggests that the sherds were collected from the owners, rather than the manufacturers of glass.

Likewise, chemical analysis of the colorless glass recovered from the Iulia Felix indicated that although all the sherds were made from the same technology--soda-lime silica, with natron used as flux--they were produced by at least two and perhaps more workshops.

Researchers Silvestri et al believe these glass fragments were collected at various Roman ports throughout the Mediterranean, and workmen shoveled the shrds into the barrel, which would have been sold at one of the Roman glass workshops, perhaps the Mediterranean port of Aquileia, known to have been an important center of Roman glass making.