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Prehistoric skeleton buried adorned with copper alloy goods.

Experimental Color Chart Reveals the Original Beauty of Prehistoric Copper Goods

An international team of Serbian and UK researchers claim to have developed a Cu-As-Sn (Copper-Arsenic-Tin) color ternary diagram, which will help scientists to uncover the original colors of ancient artifacts now patinated through age and exposure.

Evolutionary Copper-Arsenic-Tin Color Ternary Diagram Developed

Despite various studies of ancient gold metallurgy being fully supported by modern research in color characteristics of gold alloys, the color properties of major prehistoric copper alloys, such as arsenical copper and tin bronzes, have remained vastly understudied as they are not easily accessible to the western scholarship. That is about to change, however. As Phys Org reports , a new study conducted by an international team of Serbian and UK researchers and published in the Journal of Archaeological Science, suggests that it has developed a Cu-As-Sn (Copper-Arsenic-Tin) color ternary diagram that promises to uncover the original colors of archaeological artifacts now patinated through age and exposure.

64 metal samples using variable copper-tin-arsenic compositions created to use in the study

64 metal samples using variable copper-tin-arsenic compositions created to use in the study 
(Image: M. Radivojevic)

The Importance of Color in the Progress of Metal-Making Technologies

The motive behind this study was the discovery of the world's earliest tin bronze artifacts four years ago in Serbia. Since then, there has been an endless debate regarding the importance of color in the evolution of metal-making technologies.

“Given the acknowledged importance of aesthetics in ancient metallurgy, we decided to experimentally replicate the most common prehistoric alloys, made of binary and ternary combinations of copper, arsenic and tin and produce a color chart that comes the closest to showing the true 'bling' of such artifacts in the past. We were inspired by modern jewelry making where similar color charts are used to explore properties of gold-copper-silver alloys,” Dr Miljana Radivojevic, lead author and researcher at the McDonald Institute for Archaeological Research, University of Cambridge, said as Phys Org reports .

Professor Zeljko Kamberovic, leader of the Serbian team from the University of Belgrade Faculty of Technology and Metallurgy, focused on the laboratory’s impressive facilities, which allowed the experimental casting of 64 binary and ternary alloys in this study, "Our laboratory is one of the few in Europe to hold a license to experiment with arsenic, which is why we were approached to develop the study and produce 64 metal samples of variable copper-tin-arsenic compositions," he added.

Prehistoric hoard including copper and bronze good as well as pottery.

Prehistoric hoard including copper and bronze good as well as pottery. ( CC BY-SA 2.0 )

The “Exotic” Golden Hue of the Balkans

As an initial case study, the researchers plotted the composition of the world's earliest tin bronze artifacts. Dr. Radivojevic explained the significance of the “exotic” golden hue from the Balkans, "The copper-tin-arsenic ternary color charts enabled us to re-evaluate the claim that early tin bronzes in the Balkans had a distinctive golden hue,” she said as Phys Org reports and added, “It is now highly likely that the production of this new alloy in the Balkans at the same time as gold could have been dictated by the demand for the 'exotic' golden hue, or its closest imitation.”

On the other hand, Professor Martinón-Torres from the UCL Institute of Archaeology, where chemical and colorimetric analyses for this study were conducted, overlooks the local character of this research and suggests that the study’s finds have a way more ecumenical importance, “This research, although driven by the case study in the Balkans, yielded a valuable representation of color of the most commonly produced prehistoric alloys worldwide. We now have the means to bring the original shine to the items that have lost their original aesthetic appeal during several millennia of deposition below ground,” he noted via Phys Org.

Ultimately, Dr. Radivojevic predicts that these color charts will be globally used in teaching or museum exhibits and will help students and museum visitors from all over the world to envisage how most of the ancient metal artifacts really looked a few thousand years ago.

Top image: Prehistoric skeleton buried adorned with copper alloy goods. (Image: E. Pernicka)

By Theodoros Karasavvas

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