Lycurgus Cup Changes Colour by Tiny Nanoparticles

Lycurgus Cup glows red behind.

The Lycurgus Cup is a 4th-century Roman glass cage cup.

Dichroic glass has tiny gold and silver nanoparticles inside.

Particles about 70 nanometers across make the cup’s colour shift.

The silver-gold alloy scatters blue light, making red glow.

The cup’s glass behind figures is hollowed for even colour.

King Lycurgus is trapped by a vine in the cup’s design.

Dionysus and followers taunt Lycurgus in the glass artwork.

The cup likely came from Alexandria or Rome, 290-325 AD.

The Lycurgus Cup measures 16.5 centimeters tall.

The glass was cut back to create a delicate cage of figures.

The Lycurgus Cup is the only complete Roman dichroic cage cup.

The cup was used at Bacchic feasts to show its colour change.

Gold and silver were likely added accidentally in the workshop.

The Lycurgus Cup shows red when light shines through it.