X-Ray Fluorescence (XRF) analysis is a technique which can be used to determine the composition of an artifact. This can give clues to the technology of construction, period, culture and use of an object. In certain artifacts XRF can show that an item may be constructed over a comparatively long period of time.
One such item is a mirror from the collection. Copper was the main metal used in ancient Egypt, and a relationship between the composition of the metal and it's age can be established. In the case of the ancient Egyptians the composition of the copper, and it's alloys, developed as the available smelting technology advanced. The earliest copper finds are dated at approximately 5000 BC and contain a high level of impurity. By the time of the 1st Dynasty c.3000 BC arsenic was alloyed with the copper to improve the metal. This development of the alloys advanced through bronze, a copper-tin alloy, to brass which only became available during the Roman period (30 BC).
The mirror was examined using XRF. It was thought to date from the New Kingdom (1550 to 1069 BC), but the analysis showed that the composition of the mirror varied. The main oval and an attached figure were made of bronze, but horns on the mirror were made of brass. These horns must therefore date from the Roman period. It is possible that the brass horns were later additions to a much older mirror.
The bronze oval and figure also showed different compositions. The oval contained little lead, whereas the figure had a high lead content. This is explained by the method of construction. A higher lead content would make the metal more fluid, and easier to pour into a mould. A harder metal, with less lead, was used for the oval section which would make it easier to beat into shape then polish.
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