A picture lives by companionship, expanding and quickening in the eyes of the sensitive observer. It dies by the same token. It is therefore a risky act to send it out into the world. How often it must be impaired by the eyes of the unfeeling and the cruelty of the impotent who would extend their infliction universally.
Mark Rothko, 19471
On the 7 October 2012 Mark Rothko’s Black on Maroon 1958 (Tate T01170), one of the Seagram Murals, was tagged with a highly fluid, heavily coloured black ink (figs.1 and 2). Tate’s nine Seagram Murals have iconic status within the collection and although only one of them was targeted, their interrelatedness meant that the vandalism was particularly devastating. The visible damage was significant and as the painting was delicate, degraded and unprotected by glazing or a coherent varnish layer, the attack presented a serious conservation challenge. In the days following the incident, much discussion ensued as to the most appropriate method for reversing the damage. The treatment team began with a review of existing research on Rothko’s paintings, which was then combined with new investigations into the effect of the graffiti on the painting’s surface. Little was known about the ink, its properties and most importantly its reversibility, and so research into the characteristics and solubility of the ink was also undertaken. The testing and application of potential solvent systems could not be carried out on such a delicate painting, hence it was decided that a testing surface – a ‘representative sample’ – would have to be devised. The test sample had to behave in a manner similar to the painting and so needed to comprise a similar stratigraphy and materials. To achieve this, an in-depth study of Rothko’s working practice, his materials and techniques was carried out.
Rothko’s working methods
Little is known of Rothko’s technique and he preferred it that way. He exalted in the idea of secrecy and silence. As he himself put it, ‘some artists want to tell all like at a confessional. I as a craftsman prefer to tell little’.2 Elizabeth Jones, a conservator who helped Rothko install his Harvard Murals in 1964, remembered that attempts to ask him about his technique or materials were swiftly dismissed as too ‘professional’ an enquiry.3
Rothko was concerned with the permanence of his paintings. Roy Edwards, his assistant when working on the Harvard Murals, remarked in 1971 that ‘He was always reading these books on how to make paintings more permanent. Very concerned with that’.4 However, as has also been well documented, Rothko was experimental and innovative with his materials, making choices that were on occasion at odds with his concerns for longevity.5 He chose light fugitive materials, either consciously or by necessity, if they suited his desired aesthetic effect.6 Although clear evidence of the artist’s hand in the making of a painting was essential to Rothko, he sought to enigmatise his processes. Most likely, he wished for the viewer to be unencumbered with contemplating all too obvious remnants of his technique, but rather to be transported beyond their physical making.7
Technical research can be viewed as an exposure of an artist’s materials and practice, sometimes against their express will. Hence the value of revealing a once guarded process should be carefully weighed against the benefits it can bring to any necessary conservation treatment and subsequent dissemination of this information.
Mock-ups and reproductions as tools for evaluating conservation treatments
Mock-ups and reproductions are occasionally used as conservation tools to understand the structure of complex artworks, the materials involved in their construction, and the techniques employed by the artist. They can also provide useful test surfaces for conservation treatments. Modern and contemporary paintings can have vulnerable surfaces that do not lend themselves to discrete testing. These ‘ersatz’ tools allow for testing comprehensive and sometimes unorthodox processes on what are often equally unorthodox original materials, thereby limiting the probability of damaging the original object. Good examples of cases in which ‘ersatz’ tools have facilitated successful treatments and have added to scholarship on an artist’s techniques are Christa Haiml’s investigation of reversible methods for the re-integration of losses to the matt and textured surface of Yves Klein’s Blue Monochrome in the Menil Collection, Houston, and Glenn Alan Gates’s reproductions of paintings by Morris Louis for the evaluation of stain removal techniques.8 Therefore a key initiative in the treatment plan was to create a sample using materials and techniques representative of Rothko’s painting in order to better understand the original and to provide an appropriate surface for testing ink removal systems.
Making the representative sample
The primary aim of the conservation treatment was to remove black ink graffiti from the bottom right corner of the canvas while minimising as much risk to the painting as possible. The treatment team initially considered producing a mock-up that would ideally look, as well as behave like the painting. However, it was quickly established that it was not possible to mimic Rothko’s idiomatic practice and technical prowess. In addition, we could not source historically accurate, original materials. Instead we decided to make a sample that ‘represented’ the knowledge available of the materials and techniques of Black on Maroon (fig.3). In particular, we relied on technical and scientific research that had been carried out in preparation for the 2008 Rothko exhibition at Tate Modern.9 The 2008 campaign was the culmination of previous attempts to examine and analyse the Seagram Murals and resulted in a useful understanding of the layer structure of the paintings and the identification of the majority of the materials Rothko used, including animal glue, egg, dammar, oil-modified alkyd resin and possibly modified phenol formaldehyde resin. However, these analyses ultimately yielded uncertain results, due to the fact that Rothko painted in very thin layers using a variety of paint media. The analysis of multifarious materials can prove challenging as it is difficult to isolate particular materials within the range of results. Nonetheless, the 2008 exhibition catalogue contains a table summarising the analytical results into the materials present in each of the Seagram Murals, including a list of pigments and media found in Black on Maroon.10 However, the exact layering of these materials, the comparative thickness of the graffiti ink and whether or not the degree to which it had penetrated the paint layers also needed to be established.
Previous minute paint cross-sections taken from the painting had yielded confusing results partly due to the extremely friable nature of the paint layers, but also because of the tendency for samples to fragment upon extraction. Further difficulties arose from the fact that the paint layers were applied very thinly and using a wet on wet technique. It was therefore decided to take a slightly larger cross-section sample, which did not fragment and allowed a better understanding of the ink-affected area (fig.4). This new section revealed more accurate information about the layer structure, enabling us to proceed with the fabrication of a test painting with a more reliable stratigraphic as well as material approximation of the original work. Based on all previous analyses and new technical, scientific and visual information, a design for the representative sample was schematised as shown in fig.3. On the right-hand side, the first layer is shown partially exposed, followed by a sequenced system of layers representing those of Black on Maroon, building up from the pigmented size layer (right) to the final resin glaze (left).
Following Rothko’s preferred choice of painting support, a heavy-weight cotton duck ‘awning-type’ canvas was acquired and attached to a wooden strainer (there seemed to be no benefit in replicating and applying Rothko’s ‘sprung’ wooden stretcher as found on Black on Maroon).11 Taking care to match the colour and consistency of the ‘ground layer’ of the painting, a size mixture consisting of rabbit skin glue, synthetic ultramarine and lithol red was prepared. This was heated to a consistency described by Rothko’s assistant Dan Rice: ‘like water this stuff’.12 The ground was brushed on with large decorators’ brushes, in imitation of Rothko’s technique.13 This layer saturated the cotton canvas as a translucent stain, satisfactorily matching that on the painting, albeit in a much more intense hue. The original lithol red pigment has undergone photochemical ageing and possibly deterioration caused by interactions between the lithol red pigment and other materials within the paint system.14 The maroon ‘field’ was the next layer to be added. Analysis and visual observation suggested that this layer comprised two separate applications of the same paint (see fig.4). The components of the field had been identified in 2008: the medium containing possible phenol formaldehyde and oil-modified alkyd resins, and the pigments including a combination of French ultramarine, barytes, kaolin, iron oxide, cadmium red, bone black and lithol red.15
While oil-based alkyd decorative paints were commonly used in the 1950s, phenol formaldehyde is a more unusual binder to find in fine art painting. Phenolic-based decorative paints were available from the early 1930s and by the 1950s they were being used as a medium for off-set printing inks and in ‘quick-dry’ gloss and flat decorative paints.16 Elizabeth Jones recalled that ‘when he [Rothko] ran out of paint he went downstairs to Woolworth’s and bought more … he didn’t know what kind it was’.17 It is possible that Rothko would have been attracted to a commercial product claiming to be a rapid drying paint as this would have facilitated the fast build-up of paint layers. Perhaps it permitted him a more expressive and gestural approach than most other available media. However, we cannot be sure how Rothko came to add this material into his painting (further technical investigations of the media of Black on Maroon are underway), which is one of the reasons why we could not produce an ‘historically accurate’ reproduction of the painting.
In an effort to recreate paint with as similar materials and properties to the original as possible, a supplier of modified phenol formaldehyde resin was located. This resin is used in printing applications and dissolves slowly in Shellsol T (Shellsol T being similar to artists’ turpentine – the most likely diluent used by Rothko). The oil-modified alkyd medium was purchased from Kremer Pigmente in Germany. According to the 2008 analysis phenol formaldehyde was found to be present in ‘abundant quantity’, and so the ratio of media chosen was two parts modified phenol formaldehyde in Shellsol T to one part oil-modified alkyd (used as supplied). In combination they produced a viscous, yellow medium and direct experience of dissolving these materials suggests that it is very unlikely that Rothko made up this paint medium himself. The subsequently admixed pigments were balanced to colour-match the ‘field’ colour of the painting and further dilution with Shellsol T was made where necessary. One application was brushed on top of the ground layer of the sample, again with five-inch decorators’ brushes. After drying for twenty-four hours, a second layer was added. An attempt was made to mimic Rothko’s technique when applying the ‘field’ layers, following Dan Rice’s recollection that ‘the physical movement was very active and very graphic’.18 The resulting ‘field’ paint film of the representative sample was glossier and a deeper red colour than that of the painting, but had a consistency and layer thickness close to the original.
In previous visual examinations a dammar glaze had been identified between the maroon field and a thin layer of orange paint, which may have been applied to seal the underlying ‘field’ paint. Consequently a film of dammar resin was next applied to the representative sample. In addition, a heretofore undocumented orange paint layer was also noted at the feathered edges of the black form; although this had not been seen on previous cross-sections of the painting, it was visually quite evident. At the time of construction, however, neither the orange pigment nor its medium had been identified. Therefore this layer was simulated using cadmium orange pigment in the same modified phenol formaldehyde/alkyd oil medium.
The black paint of the ‘figure’ was the final paint layer to be applied, again a mixture of phenol formaldehyde/oil-modified alkyd medium and kaolin, barytes, bone black as well as iron oxide and earth pigments. This combination of pigments was added to the medium and both body and colour were once again matched to the ‘figure’ paint on Black on Maroon.
Finally, the two uppermost glazes, the first consisting of whole egg and the second of dammar, were applied. The order of application of these glazes was based on careful visual examination of the painting, particularly in ultraviolet light. It appears that in most areas the dammar glaze extends over the egg glaze, as revealed by the differently fluorescing colours present in fig.4.
After completion, the sample was cut into sections to fit into Tate’s accelerated ageing chambers. Two samples containing all of the applied layers and two samples containing mostly the field and ground layers were installed. Each sample was subjected to a combination of light ageing for the equivalent of fifty years in museum display conditions, with added thermal ageing at 30°C and relative humidity cycling from 55–85% over a twenty-four hour period. The aged samples were then tagged with the same graffiti ink used by the vandal. At this stage the preparation of the test samples was completed (fig.5). A cross-section of the aged sample, containing all layers of paint, which had then been tagged (fig.6), can be compared with the cross-section from the painting (fig.4). Note the similar micro-cracks in the graffiti ink and underlying paint film.
The constituents and solubility of the ink
Designing an appropriate ink removal strategy necessarily began with an investigation of the ink. The product used to deface the painting was Molotow Coversall Cocktail ink, described by the manufacturer as visco-plastic, alcohol-based, 100% buff-resistant, ultraviolet light resistant, quick drying, permanent and weatherproof.19 The colour is listed as ‘signal black’ and the colourant is described as ‘nitrogen synthetic bitumen’ and was applied using a marker that facilitated rapid application, producing vertical drips in addition to the inscribed letters (see fig.2).
Analysis of this unusual, proprietary ink material is ongoing. However, it appears to be based on an aromatic hydrocarbon resin, with a high proportion of black dye colourant and polar solvents identified as a 2:1 mixture of ethanol and 1-methoxy-2-propanol (propylene glycol mono methyl ether) with other solvents (e.g. methanol, 2-butanone and ethyl acetate) present in trace (>1%) amounts.20
The areas covered by