Gold thickness causes problems
One of the challenges in solving the mystery was the varying thickness of the gold. Where the gold on the bracteates is thin due to stamp pressure and engravings, the scans have produced what is called CT artifacts, which are visual discrepancies between the real bracteate and the resulting CT image.
“In hospitals, artifacts occur when, for example, you’re performing a CT scan on 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,” explains Carsten Gundlach, Senior Executive Research Officer at DTU Physics.
He used the data from the hundreds of 360-degree scans of each bracteate for calculations for the spatial 3D images. Carsten Gundlach says that this method has resulted in fairly accurate 3D reconstructions of the bracteates in their folded condition. Nevertheless, the artifacts still caused trouble for Gundlach’s DTU Compute colleague, Hans Martin Kjer, who tried to digitally unfold the bracteates.
“We’ve tried to unfold one of the smaller bracteates called X17, but it’s difficult for us to define the edge 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 surfaces from each other. Ultimately, it makes it very difficult to produce a perfect unfolding where you can see all the details,” says Hans Martin Kjer.
However, the two researchers refused to give up. Through conversations with the archaeologists, they have gained an idea of which motifs are of special interest in a historical context. The focus of the project has therefore shifted from unfolding the entire bracteate to unfolding the individual parts that can give archaeologists new knowledge about Denmark in the 5th and 6th century.
'Treasure may have changed owners
Archaeologist Mads Ravn says that Denmark at the time of bracteates can best be described as what the Romans called ‘wild Germania’. Here, autocratic clan leaders ruled marked territories according to the same rules now used by biker gangs or the Mafia.
“The more wars they won, the stronger clan leaders they became. And the more gold and riches they could get for their followers, the more followers they got,” says Mads Ravn.
Judging by the size of the treasure from Vindelev, he believes that its owner must have been a very powerful, but previously unknown, clan leader. This gives the site around Vindelev, located 8km east of Jelling, the cradle of Denmark, a new and significant status as a centre of power. At the same time, the treasure from Vindelev bears a close resemblance to other gold treasures found near the town of Gudme on Funen, which is considered to have been Denmark’s most important centre of power from the 3rd to the 6th century. This leads archaeologists to believe that some of the bracteates from Vindelev may have been made by a blacksmith in Gudme. If that is the case, the gold must have changed owners at some point.
The theory is therefore that there was a close connection—perhaps an alliance—between the clan leaders of the two centres of power. “It’s possible that the gold was handed over as a gift in connection with weddings between daughters and sons from each clan,” says Mads Ravn.
In order to confirm this theory, Mads Ravn is particularly interested in seeing the motifs on the largest of the gold bracteates, which seems to have a folded twin motif in the middle. The stamps around the motif can also tell the researchers something about the origin of the bracteate and how old it is. If they turn out to bear the same stamps as the ones found in Gudme, then they were made by the same goldsmith, and the archaeologists can continue working with the theory of the close connection between Vindelev and Gudme.
“It’s a bit like a court case where the more circumstantial evidence we find, the stronger the case will be. We can’t exactly ask the witnesses who were there at the time. We rely on circumstantial evidence, and this is where DTU can help,” explains Mads Ravn.
“Research never ends”
In the digital treasure hunt for answers, DTU’s researchers have come closer to finding the evidence than before. They have succeeded in unfolding a small area with fewer folds on one of the smaller bracteates called X19.
“It’s a significantly better result than when we tried unfolding the entire bracteate. With this method, we can optimize the individual areas,” says Carsten Gundlach. However, while he still believes that the results can be improved, he thinks that the method has potential worth pursuing.
“The method opens up the possibility of piecing together the individual parts after they’ve been unfolded,” he says.