Mark Rothko, Untitled (White, Blacks, Grays on Maroon), 1963, Kunsthaus Zürich, 1971. As displayed in the exhibition gallery in the Chipperfield building

Dusty surface, apparently altered colours

Rothko’s technique of applying paint layer upon layer and allowing the layers to blend into each other created the unmistakeable, lustrous surfaces that fascinate viewers to this day. However, the predominantly matt and very dark colour fields are extremely sensitive to mechanical effects of all kinds. The smallest scratch and the slightest touch are enough to cause shininess. The formation of craquelure accelerated by vibration during transport also severely impairs the painting’s visual impact. To avoid jeopardizing the Rothko’s exceptionally good state of preservation, it has therefore travelled only three times in the last 30 years. Moreover, the Kunsthaus’s conservators were so respectful of the painting’s sensitive surface that it was not dusted during weekly gallery maintenance in the museum, and this has led to the accumulation of a clearly visible layer of surface dust.

Team discussions during pigment analysis
Non-destructive pigment analysis using a micro-XRF spectrometer
Non-destructive pigment analysis using a micro-XRF spectrometer
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Cleaning tests using a brush and black pigments
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Cleaning tests on fragile specimens under the microscope
Mobile compressor with micro-dosing device and airbrush developed in-house
Cleaning the surface of the Rothko using an airbrush
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During cleaning work on the painting
During cleaning work on the painting
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Left side with cleaned surface

Finding a way to clean the surface

Thanks to support from the Bank of America Art Conservation Project, the conservators were able to spend time concentrating on the extremely delicate task of cleaning the painting’s surface and preparing it for its new presentation in the extension. The aim was to conduct research into suitable cleaning techniques and carry out series of experiments (see images in the slider) to find the best method of cleaning the surface of ‘White, Blacks, Grays on Maroon’. Useful suggestions came in particular from discussions on technical matters with other conservators in Europe and the US who had valuable experience of cleaning the surface of Rothko paintings in their own museums and collections. These discussions made it very clear that respect for the sensitive surfaces was entirely justified, and that the planned cleaning should be carried out only using dry techniques and with minimum contact.

« Gaining maximum knowledge about a work always involves conducting technological research. » — Kerstin Mürer, Head of Conservation
« Technical discussions with colleagues made it very clear that great respect for the sensitive surfaces was entirely justified. » — Tobias Haupt, Conservator

Various series of experiments were conducted which ultimately led to the development and refinement of a cleaning method involving a soft brush – recommended by Markus Gross, Chief Conservator at the Fondation Beyeler – complemented by a controlled jet of air. The stream of air emerging from a flat spray nozzle caused a small cushion of air to form between the ends of the brush hairs and the painting’s sensitive surface, so that the hairs barely touched it (see video). This combination allowed the dust adhering to the surface to be removed almost without contact, avoiding friction and therefore shininess, and restoring the lustrous surface effect and dark depth.

Where is the ‘maroon’?

The restoration also set out to explain why the painting’s title includes the word ‘maroon’ although there is no visible ‘chestnut brown’ in the overwhelmingly black colour palette. Given its almost unbroken history of being exhibited at the Kunsthaus Zürich, it was suspected that the colours may have been altered by exposure to the lighting.

The detailed, non-destructive pigment analyses using micro-X-ray fluorescence spectrometry (micro-XRF) conducted in early summer this year in collaboration with the Swiss Institute for Art Research (SIK-ISEA) and the Swiss National Museum revealed clear indications that light-sensitive red pigments had been used. Mixing of red and blue could therefore easily have led to a type of brown. However, research in the literature and discussions with art historians indicated that Rothko probably used ‘maroon’ as a generic term for a wide variety of hues, and in this case did not therefore necessarily mean a shade of brown.

The results of the analyses, especially given the evidence concerning Rothko’s use of the term ‘maroon’, are therefore not sufficiently unambiguous to prove that the colour has changed from an original brown to the current black as a result of excessive light exposure.

Restorers: Tobias Haupt / Laura Ledwina
Project period: March – October 2021

The conservation project was made possible thanks to support from the Bank of America Art Conservation Project.