The architecture carved out of the rock is the trademark of the famous capital of the Nabataeans – but Petra has other special features to offer: Scientists report on the unusually geometrically designed wall paintings in the mysterious rock city. As part of their research project, they gained insights into the painting technique and the materials used and were also able to provide important information for the conservation and restoration of the sensitive art treasures.
They modeled entire mountain walls into facades: In their capital, Petra, in today’s Jordan, the Nabataeans created fascinating monumental buildings and works of art around 2000 years ago. The large rock mausoleums were known for a long time, but then more and more buildings and structures of the ancient city were discovered. Among them are the magnificent villa of ez-Zantur, the Wadi as-Siyyagh cave and finds in al Baida, a suburb of the Nabataean city also known as “Little Petra”. A German research team headed by the Technical University of Cologne is dedicated to researching these ruins. As part of the “Petra Painting Conservation Project”, her focus is on examining the paintings that once adorned the walls and ceilings of these buildings.
Painting of a special kind
“On the Nabatean monuments excavated so far, there are traces of wall paintings that are particularly noticeable due to their geometric shapes and for which precise planning was necessary. Roman or Egyptian wall paintings from this era do not show any comparable geometric design. The gilded decorations on the walls and the filigree stucco work are also unique, ”says Adrian Heritage from TH Köln. “The Nabataeans left hardly any written products. That is why her wall paintings are of immense historical importance for understanding this culture, ”emphasizes Heritage.
To get an insight into how the Nabataeans created these works of art from around the 3rd century BC onwards. Created, Heritage and his colleagues carried out extensive investigations on the wall paintings: “We analyzed the substrate, plaster, paint layer, pigments and the technical aids used. Because the current state of the wall paintings cannot be understood without this knowledge, ”explains Rebecca Tehrani from the TH Köln.
In the case of the villa of ez-Zantur from the 1st century AD, the scientists were able to show that the Nabatean artists first applied several layers of lime plaster and then made their paintings on the dried plaster. So it was the so-called Secco technology, explain the researchers. The investigations showed that drawings, compasses and scratches were used to construct the geometric shapes. As for the materials used, it became clear that the Nabataeans used a whole range of different pigments for the colored effects: chalk, red ocher, iron oxide, cinnabar, the mineral “Egyptian blue”, green earth or carbon.
Murals in danger
In this context, the researchers uncovered problematic consequences of the excavations: it can lead to falsified pigment changes. A comparison of photos taken shortly after the excavation of the ez-Zantur villa with current photos shows that what was once a light red layer of paint now appears gray-greenish. “We assume that the organic components in the paint have faded due to the influence of UV radiation and that the lead-containing pigments reacted chemically due to the changed climatic conditions after the excavation,” explains Tehrani.
As the team reports, the ancient structures are also threatened by other factors. Above all, so-called salt efflorescence occurs in several places – minerals that penetrate the walls and can break off the layers of paint. By means of climate monitoring as part of the project, the team was able to detect strong fluctuations in temperature and humidity between day and night, which favor the formation of efflorescence. “Animals also have access to some objects. In Wadi as-Siyyagh, bees inhabit and undermine the plaster, and in ez-Zantur, bird droppings are found on the painting surfaces. Reliable grilles on windows and doors could reduce these problems, ”says Heritage.
As the TH Köln finally reports, the team has already put its results and experiences to good use: The experts organized a multidisciplinary workshop with around 20 local specialists from the fields of archeology, conservation and tourism management. The participants learned, among other things, the documentation and analysis techniques used by the scientists. In addition, TH Köln advised the Petra New Museum on how to deal with the wall painting and stucco fragments exhibited there. All of this should serve the goal of preserving Petra’s unique art treasures and making them accessible.
Source: Technical University of Cologne