The Lycurgus Cup
Posted: Sat Sep 05, 2020 1:18 am
The Lycurgus Cup is also a very rare example of a Roman caged cup, or diatretum. The glass has been painstakingly cut and ground back to leave only a decorative "cage" on the surface with extreme undercutting. Instead of the more common abstract, geometric design, the Lysurgus Cup contains beautifully detailed human figures. It shows the mythical King Lycurgus, who attempted to kill Ambrosia, a follower of the god Dionysus (Bacchus). She was transformed into a vine that twined around the enraged king, killing him. Dionysus and two followers are shown taunting the king. Such figures on a caged cup are otherwise unknown.
http://www.grandvoyageitaly.com/history ... ges-colors
Cage cups were clearly very difficult to make, and no doubt very expensive, but this particular specimen stands apart because it exhibits a strange optical phenomenon that had stumped experts for decades. Under normal lighting, the glass appears jade green, but when lit from behind, it turns ruby red. Initially, experts weren’t sure whether the cup was made of glass, or was a gemstone. It wasn’t until 1990, that researchers figured out how the color changers were brought about.
https://www.amusingplanet.com/2016/12/l ... roman.html