Discoveries of Egyptian blue pigment at the British Museum
Egyptian blue is possibly the earliest artificial pigment ever produced. It first appeared in Egypt and Mesopotamia around 2500 BC and then spread throughout the Mediterranean world where it was widely used until around AD 800. It is a bright blue crystalline material, made by mixing sand, lime and copper or copper ore and heating them to around 850-1000°C.
A technique developed by scientists at the British Museum allows us to discover traces of Egyptian blue on ancient objects that no longer have their original paint finishes intact. To look for traces a red light is shone onto the object. Egyptian blue has a very unusual property that causes it to give off infrared light when red light is shone onto it. This is called luminescence. This luminescence cannot be seen by the naked eye, but can be recorded using a device which is sensitive to infrared light (such as a night vision camera).
Using this technique Egyptian blue has been found on a number of sculptures from the Parthenon, including the messenger goddess Iris from the west pediment. It has also been found on other objects such as the ancient Egyptian wall paintings from the tomb-chapel of Nebamun, and a stone panel from the ancient Middle East.
More about Egyptian Blue at the British Museum
Conservation scientist Giovanni Verri and curator Ian Jenkins talk about the discovery of ancient colour.