2. a short lived technology developed in fourth century A.D.
by Roman glass workers
extraordinary in several respects
firstly in the method of fabrication and the exceptional
workmanship involved
secondly in terms of the unusual optical effects displayed
by the glass - Dichroism
The Lycurgus Cup is one of a class of roman vessels known
as cage cups or diatreta
The open work decoration of the Lycurgus cup comprises a
mythological frieze depicting the legend of King Lycurgus .
3. The cup appears red in transmitted light (light source within
cup) and green in reflected light (light source outside) .
7. .Constituent Lycurgus cup Modern glass
Silicon dioxide 73% 70%
Sodium oxide 14% 15%
Calcium oxide 7% 10%
8. The experiments confirmed that the dichroism was linked to
presence of minute amounts of gold [about 40ppm] and silver
[about 300ppm] in the glass .
Minute microscopic crystals /Colloidal systems of Au and Ag can
give rise to light scattering phenomena that results in dichroic
effects.
The gold component being mainly responsible for the reddish
transmission and silver for greenish reflection .
The colours produces depend upon the precise colloidal
concentration , particle diameter , proportions and oxidation
states of certain elements , time and temperature of heating and
probably the atmosphere during heating.
