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Over the last two years, the Alte Nationalgalerie has restored two of its greatest pieces of German Romantic art, Caspar David Friedrich's Monk by the Sea and The Abbey in the Oakwood. You took samples from these pictures before the work began and examined them in the Rathgen-Forschungslabor (Rathgen Research Laboratory). Does the appeal of your work lie in the fact that you get to analyze art at such a detailed level – to get to the very bottom of it, so to speak?

Reiche: Yes, there's really nothing like it. Art is fascinating and work in the laboratory is extremely varied! The analytical methods we use allow us to examine objects ranging from prehistoric artifacts to modern art. And when the secrets of their beauty are revealed to us, it is really very moving.

Can you tell us in practical terms how that actually works? Do you go to the pictures, or do they come to you?

Usually we get a phone call or an e-mail. Then we discuss the matter and develop a strategy. If we know that we don't have to take a sample, we can take portable devices to the collections and examine the works there. That equipment includes things such as portable spectrometers that use either X-ray fluorescence or Raman spectrometry. The alternative approach is to take minute samples and bring them back to the lab – so small you can't see them with the naked eye. That's what we did with the Friedrich paintings. We then analyze each sample, moving from the least destructive method to the most destructive. Some analysis techniques leave the sample completely intact. We use those first, of course. Techniques that require the sample to be dissolved – or to lose its integrity in other ways – are reserved until the end. An example of this would be the use of chromatography or mass spectrometry when examining binding agents. The complexity of the strategy we take depends on the complexity of the questions we are trying to answer. We then compile a report, which helps the restorers, curators, or archaeologists decide how to proceed.

Tell us about working with the Caspar David Friedrich pictures.

Everyone knows that these paintings are no longer in their original condition. Our techniques allow us to analyze a picture layer by layer, to deduce the various stages of its development, and to identify the pigments and materials that have caused changes in the aesthetic impression it creates. We see whether blues have grayed over time or why other nuances of color have suddenly faded. In the case of Caspar David Friedrich, the layers of the pictures were examined on site at the Alte Nationalgalerie. In the process, we discovered not only very, very fine layers of paint, and techniques that had not been tested by scientists for centuries, but also a layer containing egg white. Together with the curators and restorers, whose expert knowledge concerning the circumstances of painting's creation is invaluable, we concluded that this layer was probably applied as a temporary protective varnish, allowing the picture to be sold without delay. So the picture was still quite fresh – the paint barely dry, so to speak – when it was taken away.

What does the Rathgen-Forschungslabor do apart from this kind of analysis?

We work on preventive conservation, in other words conservation aimed at preventing deterioration. This includes keeping climatic conditions in the exhibition rooms as constant as possible, and limiting exposure to light and other damaging influences so that the works are not harmed. Of course we also examine deterioration processes, as Friedrich Rathgen, the founder of the laboratory, did back in the nineteenth century.
We are also active in conservation science. Here we work closely with the restorers since we are not in the business of restoration ourselves.

The fourth pillar of our work is art technology, which examines suspected forgeries, among other things. We can determine precisely whether techniques have been used that did not exist when the picture is said to have been created. We can also tell whether pigments have been used that could not possibly date from that time.

We do archaeometric analysis as well, which is very closely tied to archaeological research. This includes dating, determining origin, and analyzing materials and isotopes. Material analyses are interesting, because they frequently allow us to draw inferences about social, political, or economic developments. An example from our current work is the Iron-Age coral decoration that we're analyzing together with the universities of Mainz and Paris. Corals lose their red color over time and become almost unrecognizable. Raman spectroscopy, however, allows us to identify red coral in such cases. This is extremely important, as red coral was a valuable import in the Iron Age. If we can prove that it is red coral on the decorations of these Celtic princes' graves in Southern Germany, we’ll be able to develop a better understanding of the network of trade routes to the Mediterranean area.

One of the Laboratory's main fields of work is the analysis of trace elements. Currently, however, we can offer this service only in cooperation with other museums and institutes.

So you have to cooperate with other organizations?

Yes, networking is becoming more and more important. We are now in the process of developing a European research initiative and already have 27 partner organizations. From the British Museum to the Louvre and the Prado – from Rome to Krakow – the list includes universities, museums, and research institutes. We keep each other up to date on the latest scientific findings and work together to develop new strategies for analyzing art and artifacts.

The interview was conducted by Birgit Jöbstl and Ingolf Kern.

Links for Additional Information

• Impressions of the restoration work in the Blog of the Staatlichen Museen zu Berlin (22.01.2016) (in German)
• News: "Wieder da: Caspar David Friedrichs 'Mönch‘ und die 'Abtei‘“ (in German) (21.01.2016)
• Additional information on the project
• Press kit of the Staatliche Museen zu Berlin (in German)
• Preservation and conservation of collections at the Rathgen-Forschungslabor
• Rathgen-Forschungslabor of the Staatliche Museen zu Berlin
• Alte Nationalgalerie of the Staatliche Museen zu Berlin