New study reveals manufacturing secrets of the ancient Nebra Sky Disc

A new study unveiled groundbreaking insights into the techniques used to craft the ancient Nebra Sky Disk, a 3,600-year-old artifact considered one of the most significant archaeological finds in Germany. The research, published in the scientific journal Scientific Reports, utilized modern metallographic analyses to reveal that the disk was produced using an elaborate warm forging process.

The research team conducted microstructural analyses on color-etched surfaces using light microscopy, as well as advanced methods such as energy-dispersive X-ray spectroscopy and electron backscatter diffraction. Archaeologie Online reports that these investigations focused on how the finished bronze disk was made from a cast piece, shedding light on techniques that had not been completely clarified until now.

The findings demonstrate that Early Bronze Age craftsmen were not only outstanding casters but also mastered complex bronze processing techniques at the highest level. The Nebra Sky Disk was manufactured using a complex hot forging process, involving approximately ten cycles of heating to nearly 700 degrees Celsius, followed by helical hammer forging. In each cycle, the bronze was heated, hammered into the desired shape, and annealed to relieve structural stresses in the metal.

According to Archaeologie Online, the latest investigation results clarify that Early Bronze Age craftsmen were not only outstanding casters but also mastered the further processing of bronze artifacts, such as warm forging at the highest level.

The research was conducted in cooperation between the State Office for Heritage Conservation and Archaeology Saxony-Anhalt, the Otto von Guericke University Magdeburg's Chair of Metallic Materials, and the company Delta Sigma Analytics in Magdeburg. Der Standard - Archäologie highlighted the collaborative effort that brought together experts to delve deeper into ancient manufacturing techniques.

To validate their findings, researchers created replicas of the Nebra Sky Disk. One of these was crafted by coppersmith Herbert Bauer from a cast blank to test the production method. In his experiments, Bauer had to carry out significantly more forging cycles to produce the copy than could be proven for the original disk, according to Phys.org.

Hardness measurements were conducted on both the original Nebra Sky Disk and the replicas. Phys.org reports that the mechanical properties of the samples were measured by micro hardness testing, accompanied by parallel experimental tests. The experiments revealed that the hardness of the Nebra Sky Disk matched that of the replica at a specific stage, confirming the effectiveness of the ancient techniques.

"That the investigations yielded such fundamentally new insights even more than 20 years after the recovery of the Nebra Sky Disk testifies not only once again to the extraordinary character of this century find but also to how advanced the art of metal processing was already in the Early Bronze Age," said Prof. Dr. Harald Meller, who led the research team.

The Nebra Sky Disk, adorned with gold inlays representing celestial phenomena such as the sun, moon, and stars, has long been considered the world's oldest known depiction of astronomical phenomena. Deutsche Welle notes that the disk is a unique artifact of international standing, providing a key to understanding distant worlds.

Since its police seizure and return to Saxony-Anhalt in 2002, the Nebra Sky Disk has been the subject of intensive scientific investigations. Earlier studies had provided insights into the raw materials and original coloration of the disk. Stern.de reported that the copper of the disk comes from the Alps, and the gold used for the inlays originates from the British Isles, specifically Cornwall.

This article was written in collaboration with generative AI company Alchemiq