DICHROISM OF LYCURGUS CUP

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) .

4. LYCURGUS CUP
LYCURGUS CUP

5. LYCURGUS CUP
LYCURGUS CUP

6. LYCURGUS CUP

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.