Blue Egyptian, yellow ocher and red: the Domus Aurea reveals the nature of its colors

Egyptian blue, yellow ocher and red: the House of gold reveals the nature of its colors. During recent archaeological investigations, two tanks in use during the building site phases were identified and to turn off the lime and to keep and work the colored pigments to be used in parietal decorations. Among the pigments found and subjected to microscopic analysis and spectroscopic To identify the chemical and mineralogical composition stands out the presence of yellow ocher inside an amphora, of jars containing pigments with tones of red, Like Realgar and the red earth, and above all of an exceptional ingot of the precious Egyptian blue ready to be ground.

The rarity of the discovery is due to the considerable size of the ingot (a height of 15 cm and a weight of 2.4 kg), given that the pigment is usually found only powder or in the form of small spheres, as evidenced by the discoveries made especially in Pompeii.

Egyptian blue is a pigment that does not exist in naturebut it is artificially produced by cooking, at a very high temperature, a mixture of silica, limestone rocks, minerals containing copper and sodium carbonate (the procedure for its preparation is described by Vitruvius in the ‘de architecture’). Known and used at least from the middle of the third millennium in Egypt and Mesopotamia, it then spread in the ancient Mediterranean.

In the Roman world it was used in pictorial decorations alone or associated with other pigments to create specific chromatic varieties and refined brightness effects. For example, it was used to make a colder shade for the complexion of the figures, to create the chiaroscuro in the drapery of the clothes Or, again, to give shine to the eyes. One of the major production and export centers was Alexandria of Egypt: recent discoveries have however identified others in Italic territory, such as Cuma, Literno and Pozzuoli. TO Pompeiion the other hand, the testimonies are essentially linked to the processing and use of the pigment in luxury contexts.

The discovery in Rome, in the imperial field, of such a conspicuous nucleus of Blue Egyptian once again confirms the refinement and the very high specialization of the workers who operated in the decorations of the palacewith the use of refined and expensive pigments. The study of the contexts and materials of this sector of the Domus Aurea, still in progress, could add an important contribution to the knowledge of the use of the pigment also in the Renaissance, as in the triumph of Galatea di Raffaello.

“The charm transmitted by the depth of the blue of this pigment is incredible – comments Alfonsina Russo, director of the Archaeological Park of the Colosseum – The Domus Aurea once again excites and returns the brilliance of the colors used by painters who skillfully decorated the rooms of this precious e refined imperial palace “.