Definition
Egyptian blue is a synthetic blue pigment made up of a mixture of silica, lime, copper, and alkali. Its color is due to a calcium-copper tetrasilicate CaCuSi4O10 of exactly the same composition as the naturally occurring mineral cuprorivaite. It occurs in Egypt during the 3rd millennium BC and is the first synthetic pigment to have been produced there, continuing in use until the end of the Greco-Roman period (332 BC–395 AD). The term for it in the Egyptian language is hsbd-iryt, which means artificial lapis lazuli (hsbd). It was used in antiquity (1) as a blue pigment to color a variety of different mediums such as stone, wood, plaster, papyrus, and canvas; and (2) in the production of numerous types of objects, including cylinder seals, beads, scarabs, inlays, pots and statuettes. It is also sometimes referred to in Egyptological literature as blue frit. Some have argued that this is an erroneous term that should be reserved for use to describe the initial phase of glass or glaze production while others argue that Egyptian blue is a frit in both the fine and coarse form since it is a product of solid state reaction. Its characteristic blue color, resulting from one of its main components—copper—ranges from a light to a dark hue, depending on differential processing and composition. Apart from Egypt, it has also been found in the Near East, the Eastern Mediterranean and at the limits of the Roman Empire. Although undoubtedly an Egyptian invention, it is unclear as to whether its existence elsewhere was a result of parallel inventions or whether its technology had spread to these areas.
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