V Volt

ZERO foundation: Please introduce yourselves briefly. What does your work entail? And how would you define your collaboration?

Nicole Reds and Martina Kerkhoff: The preservation of art and cultural heritage for future generations is the main focus of our work as conservators. We work on this together in the Restaurierungsatelier (restoration studio) Kerkhoff + Vogel in Bochum, which was founded in 2010 by Martina Kerkhoff and Diana Vogel.

In addition to conserving and restoring paintings, sculptures, and contemporary art, our areas of responsibility also include carrying out art-technological investigations, supervising exhibitions and the transportation of art, as well as looking after art storage facilities and collections.

In order to preserve the authenticity of the works of art as far as possible when restoring them, restoration concepts are developed that always take into account the existing basic principles of restoration ethics. These include, for example, making interventions that are only minimally invasive and ensuring that the measures implemented are as reversible as possible. The basis for this is careful analysis and the consideration of various options. These can be highly complex, especially in the case of contemporary kinetic works of art, as often it is not only the preservation of the original substance that is relevant. Other factors, such as functionality or the original artistic intention, may also be decisive in preserving the significance of the work.

Zf: You recently completed an important restoration project for the new presentation of the Kunsthalle Recklinghausen’s collection, which included two ZERO works: Hommage à Broadway by Günther Uecker (1965), and Lichtdynamo by Heinz Mack, of 1963. How did that come about?

NR, MK: Our regular clients also include some of the Ruhr art museums, including the Kunsthalle Recklinghausen. Upon joining the museum in 2021, one of the first things the new director, Nico Anklam, did was to arrange a joint inspection of the external storage facility, which revealed that there were a number of kinetic artworks not suitable for exhibition and in need of restoration. These included the works you mentioned. We then examined them more closely and analyzed their state of preservation. On this basis, we developed concepts for their restoration with the goal of restoring the works to a condition in which they could be exhibited.

Zf: What are the special features of these two ZERO works?

NR, MK: Both Hommage à Broadway and Lichtdynamo (Light Dynamo) are box objects with rotating disks inside. What the two works have in common is that the motion of the disk is an integral part of their identity. It is the rotation of the disk that makes possible the optical effects that the artist intended.

In Heinz Mack’s Lichtdynamo, the rotating disk has a structure of vertical lamellae covered in silver, using various materials. The box itself is covered by a pane of corrugated glass. When the disk rotates, the lamellae and the glass in front of it create interference, that is, an optical overlay. This results in flowing movements and an impression of water or liquid glass. It also looks as though the structures are moving in different directions, although the disk is actually rotating in one direction.

The object Hommage à Broadway by Günther Uecker contains a wooden rotating disk covered with canvas, which is studded with numerous nails and painted off-white. It is illuminated from the side so that the nails appear in a strong ray of light. The rotation of the disk produces a constant interplay of light and shadow and a complex, changing kinetic structure.

The visual movement in both objects is powered by an electric motor attached to the back. Unlike Mack’s Lichtreliefs (Light Reliefs), which reflect light from outside, Uecker’s light-kinetic nail object contains several internal sources of light. Through the inclusion of light sources, Uecker precisely defined the status of light in the work and designed it to be largely independent of external conditions. In order to enable the authentic experience of the artwork, it was therefore especially important for us to retain the originally intended lighting in its restoration.

Zf: What challenges arose during restoration of the kinetic ZERO works?

NR, MK: When they were brought to the restoration studio, both objects were in an unstable condition and no longer intact, which was why they were examined and measures undertaken for their conservation. None of the electrical elements worked; neither the motors nor the light sources they contained. In addition, there was a great deal of other damage, such as deposits of dirt, mold infestation, damage to the objects’ boxes, elements that had become detached, and corroded metal parts.

There was some evidence that the electrical system had been altered in the past, when the positions of the lamps in the corners of the box had been changed. However, it was not documented why or when this had taken place, or who did it. In order to be able to decide whether the existing construction was worth preserving or whether reconstruction to an earlier state would enable a more authentic reception of the work, the urgent question was whether Günther Uecker himself had carried out the alteration, or whether it had been authorized by him or not. We thought that this was conceivable in principle, as it was part of his artistic practice to put together and arrange the kinetic light objects variably in different exhibitions, together with Heinz Mack and Otto Piene, depending on the space. Marcel Hardung, the artist’s son, told us that technical elements of the works were actually changed in the process.

Another issue arose from the fact that new, commercially available light bulbs were screwed into the sockets. This fits in with the fact that light bulbs in exhibited works of art are often replaced when they no longer function. If this is not documented, information about which light sources were originally used is lost. However, this information is highly relevant for the appearance of the work, because there can be major visual differences between different light sources—for example, in terms of brightness, light color, beam angle, and many other specific parameters.

Another challenge was that an old sodium vapor lamp[i] was installed in the object’s box, which in the past had been operated via an outdated intermediate high-voltage transformer. Its operation would have posed a considerable safety risk, both for the artwork, as such lamps become extremely hot, and for exhibition visitors, as it contains mercury, which is toxic to the respiratory tract, and the risk of the bulb shattering is quite high. Therefore, the question arose as to how we should deal with the safety concerns and whether, from a purely technical point of view, it would even be possible to operate a sodium vapor lamp inside the work.

Zf: How important for the restoration process is background information and in-depth research in archives?

NR, MK: In addition to the art-technological examination of the objects, in-depth research is often essential for developing an appropriate restoration concept. Particularly with regard to the issues described above, we needed to gain a deeper insight into the original presentation and exhibition history of the work. Tapping into archives can make an important contribution here. Archives can provide a great deal of information, not only about the artists, their intentions, and when the works were created. They can also contain documentation of previous restoration measures or technical documents that provide information about the original materials and techniques used.

Information attached to the objects themselves—for example, exhibition stickers—can also lead to valuable information if investigated.

[i] Unlike fluorescent lamps, sodium vapor lamps do not require fluorescent luminescent material; instead, the gas discharge of sodium vapor produces visible light. Sodium vapor lamps are characterized by the intense brightness of their high-contrast yellow-orange light and are mainly used for outdoor lighting today.

Furthermore, the practice of involving the artists themselves in the decision-making process, where possible, has now become established. Also, interviewing people from the artistic environment, or contemporary witnesses, represents a possibility to obtain particularly valuable background information. Günter Thorn, for example, shared with us his knowledge about the special spotlights that Günther Uecker originally used as light sources inside the box, and also put us in contact with the artist’s son, which was most fruitful. Together with Hans Ulrich Faust (who died in 2023), he also carried out the necessary reconstruction of the electrical installation of Uecker’s light box.

Zf: ZERO art in particular works with light—including electric light sources. To what extent is the topic of sustainability relevant for you in your work or is it not possible to restore works from the nineteen-fifties and nineteen-sixties sustainably?

NR, MK: We always attach great importance to minimizing the ecological footprint of restoration by pursuing a sustainable approach. For light-kinetic ZERO artworks, for example, this can mean using LED light sources, which have lower energy consumption, generate less heat, and have a longer lifespan than older technologies. A decision such as this must be carefully weighed up, since, from the perspective of conservation ethics, the repair of technical devices or light sources is usually prioritized over replacing them. In addition, it is not always possible to simulate the lighting effect intended by the artist using LED technology. For example, the original halogen spotlights in Uecker’s light box are no longer produced today, but fortunately the lighting effect was satisfactorily recreated using LED versions, as Marcel Hardung and Günter Thorn confirmed in a direct comparison of the two light sources on site. However, there was no adequate LED replacement for the defective sodium vapor lamp, which was ultimately not put back into operation for the time being because of the hazardous substance, mercury, that it contains. The complexity of the processes when making such decisions and the possibilities and challenges that can arise when restoring light installations by the ZERO artists are elucidated in the 2018 publication Light On/Off: Restaging ZERO.[i]

[i] See Caianiello 2018 (see note 1).

Another way to reduce the energy consumption of electrically powered artworks is to put restrictions on operating them during an exhibition. To this end, recommendations can be developed and implemented using timers, motion sensors, or floor switches. At the same time, such measures reduce wear and tear on the electrical components, including the light sources, and therefore have a positive effect on the preservation of the artworks.

Zf: Dear Nicole Reds, dear Martina Kerkhoff—thank you very much indeed for these valuable insights!

This text has been translated from German into English by Gloria Custance.