"Mysterious Color-Changing Roman Glass: The Lycurgus Cup"

In the British Museum, there is the Lycurgus Cup - an ancient Roman glass vessel with a decorative pattern, dating back to the 4th century. It is capable of changing color depending on the lighting: if lit from behind, the vessel turns red, if lit from the front, it turns green. This effect is due to the presence of gold and silver nanoparticles in the glass, and scientists are unsure how the ancient craftsmen were able to achieve such an object. It is possible that in one of the workshops, there was an accidental "contamination" of the glass with gold and silver dust, and the glassmakers, most likely, did not control the technological process and did not understand the reasons for the color change.