How Was The 3,600-Year-Old Nebra Sky Disc Made? New Clues

Conny Waters - AncientPages.com - The Nebra Sky Disc, a remarkable artifact dating back 3,600 years, stands as one of the most thoroughly studied archaeological objects. Despite extensive research, the exact manufacturing process of this ancient disc remains partially unresolved. Since 2013, it has been included in the UNESCO "Memory of the World" register. Its age, aesthetic appeal, and design continue to captivate both experts and the general public alike.

The Nebra Sky Disc. Credit: Juraj Lipták, State Office for Heritage Management and Archaeology Saxony-Anhalt

The Sky Disc's creation process has been the subject of extensive scientific investigation, especially since its return to Saxony-Anhalt in 2002. Recent metallographic analyses have revealed that the disc was manufactured using a sophisticated hot forging technique rather than being cast directly into its final size. This complex process required approximately ten cycles, each involving heating the metal to around 700°C, followed by forging and annealing to relieve stress in the metal structure.

Despite its seemingly simple appearance, crafting a bronze disc with a diameter of about 31 centimeters and only a few millimeters thick is quite challenging. These findings, published in Scientific Reports, provide significant insights into the materials used and even the original color of this ancient artifact.

The research was conducted by the State Office for Heritage Management and Archaeology Saxony-Anhalt in cooperation with the Otto von Guericke University Magdeburg, Chair of Metallic Materials (Prof. Dr. Thorsten Halle), and the company DeltaSigma Analytics GmbH, Magdeburg. The latest metallographic techniques were used.

A small sample from the outer area of the Sky Disc, initially extracted in 2002 for archaeometallurgical research and later reinserted, was once again temporarily removed for further examination. This analysis employed advanced imaging techniques such as energy-dispersive X-ray spectroscopy and electron backscatter diffraction, alongside microstructural analyses on color-etched surfaces using a light microscope. Hardness measurements were also conducted. These scientific investigations were complemented by experimental tests led by experienced coppersmith Herbert Bauer from Halle (Saale), who crafted a replica from a cast blank.

The metallographic analyses revealed that the Sky Disc was created through a sophisticated hot forging process involving approximately ten cycles. Each cycle included heating to around 700 °C, forging, and annealing to relieve metal stress.

In contrast, H. Bauer's experiments required significantly more forging cycles to replicate the disc than what was necessary for the original artifact. This suggests that the original cast blank was slightly larger and thinner compared to that used in creating the replica.

"That the investigations continue to produce such fundamental new findings more than 20 years after the Sky Disc was secured not only once again demonstrates the extraordinary character of this find of the century, but also how highly developed the art of metal processing was already in the Early Bronze Age," says State archaeologist Prof. Dr. Harald Meller.

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Recent research findings highlight that early Bronze Age craftsmen were exceptional not only in casting but also in advanced bronze processing techniques, such as hot forging. Their expertise and extensive knowledge enabled them to engage in series production of numerous axes while also creating unique artifacts like the Nebra Sky Disc, which remains unparalleled from a modern viewpoint.

"In addition, the Sky Disc shows how important it is to re-examine seemingly well-known finds when new methods become available," says Meller.

The study was published in the journal Scientific Reports 

Written by Conny Waters - AncientPages.com Staff Writer