3D scans will ‘uncover secrets of Iron Age gold treasure’
Researchers are creating scans of crumpled Iron Age treasures — including the world’s largest gold “bracteate” — in order to digitally straighten them out and reveal their secrets.
Found in a field near the town of Vindelev, Denmark in 2021, the golden trove includes a total of 16 bracteates (medallion-like necklaces) and four Roman medallions.
Archaeologists believe the treasure, which totals 794 grams of gold, was likely buried back in the 6th century, and would have been owned by a powerful but unknown clan leader.
The bracteates sport intricate motifs and runic inscriptions, but many of them have been folded so extensively — some seemingly by hand, others likely by damage from a modern plough — that these designs can no longer be seen.
And unfolding them manually is too risky, researchers explained, because the bracteates might break. Fortunately, modern technology has the answer.
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Researchers are scanning crumpled Iron Age treasures in order to digitally straighten them out (Image: Conservation Centre Vejle)
Found near the town of Vindelev, the golden trove includes 16 bracteates and four Roman medallions (Image: Conservation Centre Vejle)
Archaeologist Dr Mads Ravn is the head of research at the Vejle Museums. He said: “Sometimes technology can open doors that we can’t.
“In this case, we want to get a better look at the inscriptions and images on the bracteates so we can learn more about the nobleman who owned the treasure.
“What was his position? What was his domain?
“If we succeed, we will gain a better understanding of the structure of society in the 5th and 6th century.”
The imaging technique the team is using is CT scanning — the same modality used in hospitals (Image: Mikal Schlosser / Technical University of Denmark )
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Pictured: Dr Carsten Gundlach shows off a scanned bracteat to a colleague (Image: Mikal Schlosser / Technical University of Denmark )
The imaging technique the team is using is CT scanning — the same modality used in hospitals to create detailed, three-dimensional X-ray images of people’s internal anatomy.
CT scans work by “slicing” objects into a series of cross-sections. The largest bracteate, they explained, ended up being represented by 9,600 individual images.
One of the biggest challenges the researchers faced came from how the thickness of the gold varies — creating artefacts in the resulting images.
Dr Carsten Gundlach is a senior executive research officer at the Technical University of Denmark (DTU). He said: “In hospitals artefacts occur when, for example, you’re performing a CT scan of a patient with surgical screws in their leg.
“The screws will create lines in the image, and the same thing has happened in this project.
“Our images are full of lines that wouldn’t be there if the bracteates had had the same thickness everywhere.”
Pictured: in this 3D reconstruction of the bracteate X17, the CT artifacts appear as white lines (Image: Technical University of Denmark )
Pictured: a 3D reconstruction of the folded bracteate X19. The red suface can be seen unfolded below (Image: Technical University of Denmark )
Pictured: the unfolded red region of bracteate X19 as shown in the previous image (Image: Technical University of Denmark)
Gundlach had to use hundreds of 3D scans of each bracteate to produce accurate reconstructions of the artefacts in just their real-world, folded conditions.
The next challenge — for DTU computer scientist Dr Hans Martin Kjer — came in unfolding these reconstructions to reveal the text and images on the treasures.
Kjer said: “We’ve tried to unfold one of the smaller bracteates called X17, but it’s difficult for us to define the edges of the bracteate and the exact line between two surfaces.
“When the gold has many tight folds, it makes it difficult for us to separate the surface from each other. Ultimately, it makes it very difficult to produce a perfect unfolding where you can see all the details.”
The team had better luck unfolding a small area, with fewer fold, on one of the smaller bracteates, one designated X19.
Gundlach said: “It’s a significantly better result than when we tried unfolding the entire bracteate. With this method, we can optimise the individual areas.
“The method opens up the possibility of piecing together the individual parts after they’ve been unfolded.”
The researchers are now trying to focus on the motifs that they expect to have the most historical interest — that might shine a light on Denmark in the 5th and 6th centuries.
The next step, the team said, is to digitally unfold the twin motif and the stamps on the world’s largest bracteate.
Ravn believes that the treasure may have originated in Gudme — 65 miles to the southeast of Vindelev, and Denmark’s main centre of power from the 3rd to 6th centuries — from where similar gold artefacts have also been unearthed.
If this is the case, the gold must have changed owners at some point, being passed from one clan leader to another, perhaps as a result of an alliance between the two powers.
Being able to see the motif of the largest bracteate and the stamps around its edges would allow a comparison with the finds from Gudme, to put Ravn’s hypothesis to the test.
Kjer concluded: “There are still many challenges to solve. Of course, it’s annoying that you can’t just finish things up and move on.
“But you can always do more. Research never ends!”
