ABSTRACT
Let us start by looking at the famous Lycurgus cup from the Roman era [1]. It is shown in Figure 3.1a. The appearance is green, but if a small lamp is put inside the cup the transmitted light looks red. The more modern vase from Victorian times in Figure 3.1b looks red both in transmission and in reection. Both objects consist of glass to which gold has been added so that nanoparticles have been formed as inclusions. Objects of equal beauty were made at other times, too, and, for example, copper nanoparticles were used to create stunning luster on some Renaissance pottery [2]. This chapter will dwell on the theoretical models for understanding the beautiful colors formed in the glass and why they may look so different, depending on the illumination.
