Coatings Xperience Rothko Restoration: Advancing the Science of Art Conservation

rt conservation scientists and art conservators Developing solvent solutions often possess similar skill sets that include an extensive understanding of analytical “DCM, as part of Dow, is well-positioned to provide methodsA and physical characterization techniques, knowl- support to the art conservation community because the edge of the chemistry of numerous types of art media, company has, in addition to extensive knowledge regard- extreme patience, and a real passion for art. However, how ing acrylic coatings technology, significant expertise with they attain these skills and their backgrounds can vary. In solvent and cleaner chemistries through its industrial the United States, the title “conservation scientist” is not solvents and cleaners businesses. We are leveraging defined by a formal university or licensing regimen; most that combined knowledge and applying it to specific chal- scientists hold degrees in chemistry or related fields. On lenges in the art conservation field,” says Keefe. the other hand, the terminal degree for art conservators is For example, using Dow’s high throughput technol- a Master of Science in art conservation. A recent collabora- ogy, she has developed a robotic system for more rapid tion brought these two disciplines together for the benefit analysis of the cleaning solutions she develops. After of art lovers everywhere. careful consideration of the physical properties of the A once-declared art major turned coatings scientist, cotton swabs typically used by conservators, Keefe used Dr. Melinda Keefe, with support from her employer Dow, a rigid foam and cotton batting to mimic the swabs, and has been fortunate to combine those two interests via attached this device to a robot that then cleaned arti- an ongoing collaboration between Dow Coating Materials ficially soiled dried acrylic paint films. A high-resolution (DCM), the Tate Modern art museum in London, and the imaging system provided detailed data that she used to Getty Conservation Institute. The collaboration is focused determine the “percent clean” value for each sample, on improving wet cleaning systems for the conservation which in turn enabled comparison of multiple samples. of modern acrylic paintings and other unvarnished works Importantly, the results using the robot have been com- of art. This collaboration provides opportunities for Keefe pared to the results obtained at Tate for more traditional to present new solutions to conservators for evaluation. manual cleaning of artificially soiled acrylic paint films More recently, she and colleagues Felipe Donate, of Dow’s with good agreement, according to Keefe. “With this Oxygenated Solvents business, and Chris Tucker, of Dow’s system, we are able to explore many different possible core R&D business, were able to provide support to the aqueous and aliphatic hydrocarbon-based systems, art conservation team at Tate Modern when they faced the including a broad range of surfactants, solvents, micro- challenge of restoring the Mark Rothko painting Black on emulsions, etc., that might have potential for use in the Maroon (1958), which was damaged by graffiti in 2012. restoration of acrylic paintings,” she observes. Promising cleaning solutions are sent to Tate’s senior conservation scientist, Dr. Bronwyn Ormsby, for systematic evaluation. Those that the Tate staff find in- teresting are then shared with attendees at workshops

Photo showing graffiti-damaged Rothko painting.

The painting is returned to its display space at Tate Modern following the successful collaborative conservation effort. July 2014 20 COATINGSTECH Rothko Restoration: Advancing the Science of Art Conservation

for art conservators hosted by the Getty Conservation Institute, where the conser- vators use them in hands-on sessions. The feedback from these workshops is then used to improve the systems at Dow.

“This development cycle is ongoing Tate Modern art museum and leads to continuous advances in cleaning technology for use in art con- servation,” Keefe asserts. “Specifically, solvent-based proprietary graffiti product research and testing, ink removal, and our goal is to develop a range of effective that is designed to stain. In addition, surface reintegration. cleaning solutions, because every con- Ormsby notes that Rothko's paintings are The R&D stage involved testing of servation project has unique challenges difficult to conserve due to his choice artificially aged painted samples prepared and no one cleaning system will be appli- of painting materials and technique. In using information about the materials and cable for all of them. Conservators need this case, that involved sophisticated structure Rothko used in Black on Maroon. a ‘toolbox’ of different cleaning solutions tonal variation and subtle surface effects Samples of the ink were also analyzed that have a range of performance char- created by multiple thin applications of at Tate and by external collaborators and acteristics,” she adds. This work, along paints and coatings of different media contracted scientists. For example, the ink with other emerging scientific research, (both natural and synthetic polymers) solvent content was determined by gas is adding to that toolbox. and pigment mixtures, some of which chromatography with a flame ionization are light-fugitive and several of which are An advantage of working for Dow is detector, and the polymeric and colorant soluble in the same range of solvents as that Keefe has access to the company’s constituents were characterized and prop- the graffiti ink. Furthermore, the effects proprietary solvent database and soft- erties explored via an extensive suite of of natural aging, particularly of the local- ware program (CHEMCOMPSM Solvent techniques and found to be based on a ized dammar resin and egg glazes thinly Property Modeling Service) designed to modified polyaromatic hydrocarbon resin applied over black paint, contributed to determine solvent candidates for a given of low molecular weight. “The main aim the complexity of the treatment. These material. The database contains many was to explore the solubility of the ink so glazes did block penetration of the ink hundreds of solvents, along with their that an appropriate, low-risk solvent sys- into the black paint; however, with no physical properties information, and tem could be designed to remove the ink glaze over the porous maroon paint with uses the Hansen Solubility Parameter from the painting,” Ormsby says. its network of fine micro-cracks, the flow (HSP) of the material to be dissolved as of the graffiti ink through the painting Additional analyses and examina- the key input. In fact, Keefe used this structure was facilitated. tions focused on the painting surface and database and software program to help interactions between the paint and the generate a potential list of solvents for “The overall complexity of the graffiti ink. The Dow scientists determined cleaning the damaged Rothko painting. chemistry, physical properties, and the HSP of the ink and generated a list appearance of the painting; the of potential solvents using the company’s differences in graffiti ink thickness and proprietary database and software, con- The challenge of penetration; and the fact that this unique sidering the ink properties and the prop- Black on Maroon (1958) problem had never been encountered erties of an aged alkyd as a surrogate for before necessitated a most thorough, the actual painting. Keefe and Donate Mark Rothko's painting Untitled, ethically sound, collaborative, and first eliminated solvents with undesirable Black on Maroon (1958, Tate T01170) responsible approach,” Ormsby observes. health, safety, and environmental profiles, was extensively damaged by black ink in To manage the restoration project, and then investigated the remaining October 2012, with a total of 45 marks/ a Treatment Team and Rothko Project leading candidates by applying the sol- letters applied to the painting surface Advisory Group were established and vents to an acrylic-primed canvas. They over a large area of the lower right cor- operated in tandem to ensure that the ultimately provided the Tate staff a list of ner. The challenges for the conservation approach, research, support, ethical 16 solvents, solvent blends, and micro- treatment were both complex and nu- considerations, and conservation treat- emulsions, including ethyl lactate, several merous, according to Ormsby. ment were explored and carried out glycol ethers and glycols, n- and iso-butyl The ink was a fast-drying, highly col- to the highest possible standards. The alcohol, and dimethyl sulfoxide. “The in- ored, “permanent,” highly penetrating, stages of the project included initial formation provided by Dow saved valuable

July 2014 COATINGSTECH 21 Extensive analysis of Black on Maroon itself was also necessary. Analysis of the interactions between the painting and the applied graffiti ink was achieved through examination of the painting under light microscopes, in ultraviolet light, and with high-resolution digital micro- scopes. Samples of paint in the ink-affected area were also taken (with permission), mounted, and investigated as cross-sections using light microscopy, UV microscopy, scanning electron microscopy, Fourier transform infra- red imaging, and other mass spectrometry techniques. Canvas samples were also extensively analyzed. “This extensive analytical effort was necessarily collaborative, as it is rare that any one museum labora- tory can offer all of these techniques,” Ormsby com- ments. The analytical team consisted of scientists from Tate; the National Gallery of Art, Washington D.C.; Jaap Boon Enterprises, Amsterdam; HIROX, France; The Yale Center for British Art, New Haven; and the University of Delaware, Delaware. The ink removal phase lasted approximately seven months. The process involved application of the solvent blend (with occasional amendments) using a small brush, swelling of the ink for a few seconds, and then careful blotting of the softened ink with a highly absor- Dr. Melinda Keefe alongside the restored Black on Maroon. bent tissue. “Each letter was removed slowly and me- ticulously, working on an area of approximately 4 mm2 time at this early stage of the project and was very useful at any one time and evaluating the results in-situ with in guiding the ink removal process,” notes Ormsby. various forms of microscopy,” Ormsby says. The list of 16 solvents was ultimately expanded to The final stage of the process involved the reintegra- approximately 80 options/permutations, and solvent tion of the surface, or the retouching phase. Here, re- gelling options, suction techniques, solvent application versible materials were used to recreate the lost glazes methods, and the use of various tissues for the removal and to disguise remnants of the ink left in the paint. of the softened ink were also evaluated over a four- These materials included water-based watercolors and month period. “Solvents were assessed for their speed water-resoluble acrylic media with the addition of stable of ink removal, evaporation rate (which affects working pigments and minerals, such as mica, to amend gloss time), toxicity, clearance, blanching effect, tendency and mimic the velvet-like surface of the painting. The to bleed or spread beyond boundaries, and the most aim of the treatment, according to Ormsby, was to elimi- vital aspect—their effect on the underlying paint layers,” nate all visual evidence of the damage in gallery condi- Ormsby explains. tions and to return the work back into the display space at Tate Modern. This was achieved on May 13, 2014. The solvents were systematically tested on ink applied to a white acrylic primed canvas (where it was easy to see the effects), the aged representative The importance of sample, and an archival primed canvas kindly provided collaboration by the Rothko family, who were very supportive of the project throughout, according to Ormsby. Finally, a Apart from enabling the return of the painting to Tate group of six solvents was chosen to evaluate on the Modern, one of the highlights of this project for Ormsby painting, and ultimately a blend of benzyl alcohol and was witnessing the collaborative effort of many people ethyl lactate was selected that offered a slow swelling and institutions in support of this unique conservation action facilitating a controllable ink removal process treatment—including within Tate, within the project advi- with minimal impact on the underlying paint films. sory committee, within the international art and heritage “Fortunately, the aromatic hydrocarbon-based ink was science communities, and beyond into the coatings different enough from the painting to be slowly dis- industry. “Every small and large contribution proved vital solved while minimizing the risk to the underlying paint- to the success of the project, which has also allowed us ing materials which (at least) include egg, dammar, the rare opportunity to educate the world about the vital oil, alkyd resin, animal glue, and a range of pigments,” behind-the-scenes work of dedicated museum profes- Ormsby adds. sionals,” she asserts. CT

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