Roman bowl
This Roman glass bowl was cast moulded in Alexandria in the early part of the 1st century AD. The bowl has an attractive metallic sheen or iridescence, but it was not like that when it was first made. Over the years water and atmospheric pollution have created many thin layers of glass on the outside. As light penetrates the surface and is reflected from each layer it is split into its component colours to give a rainbow effect. Because the colours come from light, not added pigment, the effect changes as the viewing angle is altered.
