Vitrum Flexile, or flexible glass. Although lost in legend, three different authors provided an account of a glass that could be dented and then repaired in Rome’s first century. According to the Corning Museum of Glass, Petronius (who died in 63 A.D.) told of a drinking vessel presented to Emperor Tiberius (reign 14-37 A.D.). The vessel was thrown to the ground, and though dented, the glassmaker was able to remove the dent with a hammer.
Pliny told a similar story in his encyclopedia, completed around 78 A.D., although his story goes on to say that the glassmaker's workshop was destroyed so that the value of copper, silver and gold would not be affected by the vitrum flexile.
Dio Cassius provides the third story, in which an architect, who fell out of favor with Tiberius, provided the aforementioned demonstration of denting a glass vessel, then repairing it with his hands.
Unfortunately, no other accounts of vitrum flexile exist beyond these stories. As polymer scientists, we naturally assume that the vitrum flexile was not glass, but rather an early form of plastic, given its mechanical behavior and appearance. Perhaps it was formed of a natural resin, or from a crude polymerization. Ethylene gas was known to be in the Mediterranean around this time (the suspected source of the Oracle of Delphi’s visions). Did a resourceful Greek manage to perform some early free radical polymerization?