The imperial crown was created thanks to medieval high-tech

Ugly, but important: This is probably the most concise, but nonetheless accurate verdict on the imperial crown. It was the central symbol of the Holy Roman Empire, which from the late 15th century still bore the addition of "German Nation" in its name. An unknown visitor to the treasury in the Vienna Hofburg coined this formula about the insignia. It sums up the discrepancy between the somewhat disappointing aesthetic quality of the piece of jewelry and its enormous importance for half a millennium of Central European history.

Because the imperial crown symbolized the dignity of the rightful German king and candidate for the imperial title. Not all rulers between the 10th and 16th centuries were crowned in Aachen Cathedral, but at least 30 of 36 kings between Otto I and Ferdinand von Habsburg received their dignity in the former Palatine Chapel of Charlemagne. Many of them probably had the official imperial crown placed on their heads.

In order to uncover as many secrets as possible of this gem, the Kunsthistorisches Museum (KHM) Vienna, to which the Treasury belongs organizationally, started the "Crown" project at the beginning of 2022. The octagonal crown, weighing three and a half kilograms and set with 116 precious stones and around 200 pearls, will be examined more closely than ever before by the end of 2024. This does justice to one of the central tasks of museums, not only to preserve, but also to research, said KHM director Sabine Haag in an interim report at the end of January 2023.

The scientists are hoping for clues as to the exact date of origin, because it makes a difference whether the crown circlet, which consists of eight connected plates, was created in the 10th century for Otto the Great - or around 150 years later for the first Staufer king Konrad II. What is certain is that Charlemagne never wore this crown on his head, even if Albrecht Dürer depicted it differently in his well-known idealized portrait from around 1511.

Natural scientists and art historians are also interested in the production methods. In the first year of the project, around 60,000 photos were taken, enlarged up to 2500 times; In addition, the 172 stones used on the crown circlet, forehead cross and crown bow were examined for the first time using modern methods. So far, there has only been an optical classification of some gemstones, dating back to 1977. Findings include that a red spinel (similar to a ruby) may have been exposed to a temperature of around 1,000 degrees to enhance its chromaticity. At the beginning of the High Middle Ages, this was real high-tech.

If you look closely at the imperial crown, you can see that the unknown mocker in the Viennese treasury was absolutely right: From a purely artistic point of view, the crown is hardly a piece of jewellery. The numerous stones are all too randomly attached to the eight plates, the settings appear rather coarse (to be precise, there are 71 sapphires, 50 garnets, 20 emeralds, 13 amethysts, four chalcedonies, three spinels and eleven differently colored glasses). At least the political program that the crown symbolizes is clear: "Per me Reges regnant" is written on the enamel plaque with Christ in the middle, i.e.: "Through me the kings rule."

Although the crown has always been one of the three most important insignia of the empire, it has been repeatedly damaged in use over the centuries. When someone fell to the ground, for example, stones broke out and had to be replaced, explains project manager Franz Kirchweger: “What we are doing here is basic research in the best sense of the word.”

However, some modern examination methods had to be ruled out from the outset. While computer tomographs are ideal for x-raying mummies, they could be used with the imperial crown: the high radiation energy could change the color of the gemstones. On the other hand, methods such as X-ray fluorescence analysis and Raman spectroscopy (named after the Indian Nobel Prize winner C.V. Raman) have proved useful, in which molecular structure can be determined using lasers.

Classic art historical methods are also used. Around 16,000 relevant entries have already been viewed in international image databases; The imperial crown has been identified on around 550 illustrations to date. Among them are the colored copper engravings of the imperial regalia created in 1751 by the Nuremberg artist Johann Adam Delsenbach on behalf of the magistrate of his hometown. Most of the illustrations, however, are only quite free fantasy creations - hardly any artist came close enough to the crown to document it in detail.

The "Crown" project costs a total of 1.3 million euros, which is paid for by sponsors such as the Ernst von Siemens Art Foundation and the Rudolf August Oetker Foundation. Project partners of the Vienna Museum include the Louvre in Paris, the Prussian Cultural Heritage Foundation in Berlin and various institutes in Belgium, Italy and Germany. This is how the symbol of power has a cross-border effect today.

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