This talk was a good example of collaborative art historical and material science research. Two of the three authors, Kaslyne O’Connor and Ariel Pate, discussed a study that revolved around two gum-platinum prints by Edward Steichen from his 1904 “Moonrise” series in the collection of the Art Institute of Chicago that had titles and dates under question. Each print had been referred to by different names (“Midnight Lake George” and “Moonlight Lake George“), and varied in tonality and surface sheen (you will notice that the prints have the same titles and dates on the Art Institute of Chicago website). Furthermore, the image in one of the prints is flipped horizontally.
A letter from Steichen to Stieglitz talks about “Midnight Lake George” being a platinum print followed by blue print, then greenish gum varnish. This letter is a valuable piece of information, along with X-Ray Fluorescence and Fourier Transform Infrared Spectroscopy that gave characteristic signals for Prussian blue, platinum (“Midnight…” had more), palladium, mercury (traces in “Midnight…” only), chromium, iron (“Moonlight…” had more), and lead for both prints. Still to be determined is the distribution of Prussian blue throughout the print, which would suggest the cyanotype process vs. a Prussian blue watercolor wash over the entire surface of the print. Clip marks at the print edges did displace the gum layer, thus revealing a blue layer below, which could be a hint that the cyanotype process was used. Examination of “Midnight…” under ultraviolet light exhibited a green fluorescents characteristic of linseed oil.
A Camera Works supplement from 1906 refers to “Moonlight…”. A 1910 Albright Art Gallery catalog for the “International Exhibition of Pictorial Photography” refers to “Moonlight…” having been made using a platinum gum process “peculiarly [Steichen’s] own”. Ultimately, a timeline was proposed by the authors using the information gathered from this research, which supports the 1904 (“Midnight…”) and 1909 (“Moonlight…”) printing dates for each. More apt titles were also proposed–”Road to the Valley, Moonrise” for “Midnight…” and “Road to the Valley, Moonrise Lake George” for “Moonlight”. Something that was noted that I found to be particularly interesting was that Steichen became less “poetic” in his later years, and retitled many of his prints.
Also to note, this project was born out of a previous project to create the website The Alfred Stieglitz Collection, a rich resource recommended to visit.
The presenter, Linda Stiber Morenus, began her discussion of these complex prints with a description of the printing process. Chiaroscuro woodcuts were intended to emulate chiaroscuro drawings, which were comprised of black chalk shadows and white chalk highlights on colored paper. Color oil-based printing inks were first used to print 14th-century textiles, being used on paper by the mid 15th-century. The chiaroscuro woodblock prints required two to five separate woodblocks, inked with different shades lighter and darker than the midtone colored paper.
In order to better characterize the media, Morenus collaborated with art historian Takahata, and conservation scientists Eng and Rimbaldi from the Los Angeles County Museum of Art (LACMA). In addition to prints at LACMA, the team studied prints from the British Museum and Library of Congress. Out of over 2000 surveyed woodcuts, 72 were studied in depth, with X-ray Fluorescence (XRF), Fiber Optic Reflectance Spectroscopy (FORS), and Raman spectroscopy. Inorganic compounds were indicated by XRF analysis. FORS was especially helpful for detection of indigo. Raman spectroscopy provided additional information about organic colorants.
Renaissance artists’ manuals, such as Cennino Cennini’s Libro dell’Arte guided the research by providing information on the most likely colorants for printing inks. Inorganic pigments included lamp black, lead white, ochres, vermillion, verdigris, and orpiment. Organic pigments included indigo and a variety of lake pigments.
After providing background information, the presenter began to focus on deterioration and conservation of the chiaroscuro prints. The prints from the Niccolo Vicentino workshop had a high lead content. The inks typically had a low vehicle-to-pigment ratio, tending to turn gray around the edges, due to the presence of lead sulphide. Verdigris corrosion was also a common problem, as found on “Christ Healing the Paralytic Man” by Giuseppe Niccolo Vicentino, as well as 13 other prints from the same workshop. Typical copper-induced paper degradation included yellow-brown halos around inked areas and cracks in the paper.
Fading and discoloration were major problems for the organic colorants, such as indigo and the yellow lakes. Morenus compared copies of Ugo da Carpi’s “Sybil Reading a Book” in the British Museum and the Library of Congress, finding clear evidence that the indigo in the British copy had faded. The British Museum had confirmed the presence of indigo through Raman spectroscopy. At least 8 of the prints were found through XRF to have high levels of calcium in the same areas where indigo had been identified, suggesting the presence of chalk-based lakes. Organic greens had shifted to blue or brown where organic yellows had faded or become discolored.
The presenter concluded with suggestions and caveats for conservation treatment. First, she advised conservators to exercise caution in aqueous treatment, in order the preserve the topography of the prints. The woodblock creates a relief impression in the paper, and the layering of the inks adds another level of texture that might be altered by humidification, flattening, washing, or lining treatments. The low binder content also makes the inks more vulnerable to saponification and loss during alkaline water washing. Morenus warned that the hydrogen peroxide color reversion treatment for darkened lead white would be particularly risky, because the white lead sulphate end product has a lower refractive index than basic lead carbonate original pigment. This means that treated lead white becomes more translucent, and the lower “hiding power” shifts the tonal balance of the print to appear darker overall.
For exhibit recommendations, Morenus suggested that we should always expect to find fugitive organic colorants in chiaroscuro prints, so exhibit rotations should be planned accordingly. Maximum exhibit conditions should be 5 foot-candles (50 lux) of visible light for 12 weeks of exposure, no more often than every three years. She also indicated that overmatting should be avoided to reduce the risk of differential discoloration.
During the Question and Answer period, Morenus clarified the color order used in printing. Some prints were inked from dark to light, but most were printed with the lightest color first.
I thoroughly enjoyed learning about these beautiful prints, but I think that the discussion of the lead white conversion treatment-induced refractive index shift was the most important “take-away” from the presentation.
NYC’s Museum of Modern Art owns sixteen Piet Mondrian oil paintings, the most comprehensive collection in North America. From this starting point, conservator Cynthia Albertson and research scientist Ana Martins embarked on an impressive project, both in breadth and in consequence—an in-depth technical examination across all sixteen Mondrians. All examined paintings are fully documented, and the primary preservation goal is returning the artwork to the artist’s intended state. Paint instability in the artist’s later paintings will also be treated with insight from the technical examination.
The initial scope of the project focused on nondestructive analysis of MoMA’s sixteen oil paintings. As more questions arose, other collections and museum conservators were called upon to provide information on their Mondrians. Over 200 other paintings were consulted over the course of the project. Of special importance to the conservators were untreated Mondrians, as they could help answer questions about the artist’s original varnish choices and artist-modified frames. Mondrian’s technique of reworking areas of his own paintings was also under scrutiny, as it called into question whether newer paint on a canvas was his, or a restorer’s overpaint. Fortunately, the MoMA research team had a variety of technology at their disposal: X-Radiography, Reflectance Transformation Imaging, and X-ray Fluorescence (XRF) spectroscopy and XRF mapping were all tools referenced in the presentation.
The lecture discussed three paintings to provide an example of how preservation issues were addressed and how the research process revealed information on unstable paint layers in later Mondrian paintings. The paintings were Tableau no. 2 / Composition no. V (1914), Composition with Color Planes 5 (1917), and Composition C (1920), but for demonstration’s sake only the analysis of the earliest painting will be used as an example here.
Tableau no. 2 / Composition no. V (1914) was on a stretcher that was too thick, wax-lined, covered in a thick, glossy varnish, and had corrosion products along the tacking edges. Research identified the corrosion as accretions from a gold frame that the artist added for an exhibition. The painting has some obviously reworked areas, distinguished by dramatic variations in texture, and a painted-over signature; these changes are visible in the technical analysis. The same research that identified the source of the corrosion also explained that Mondrian reworked and resigned the painting for the exhibition. XRF mapping of the pigments, fillers, and additives provided an early baseline of materials to compare later works to, as the paint here did not exhibit the cracking of later examples. Ultimately, the restorer’s varnish was removed to return the paint surface to its intended matte appearance, and the wax lining was mechanically separated from the canvas with a specially produced Teflon spatula. Composition no. V (1914) was then strip-lined, and re-stretched to a more appropriate-width stretcher.
It is possible to create a timeline of Mondrian’s working methods with information gleaned from the technical examination of all three paintings. His technique had evolved from an overall matte surface, to variations in varnish glossiness between painted areas. XRF analysis demonstrated a shift in his palette, with the addition of vermillion, cobalt, and cadmium red in his later works. XRF also revealed that the artist used registration lines of zinc and lead whites mixed together and used on their own. Knowing the chemical composition of Mondrian’s paint is vital to understanding the nature of the cracking media and identifying techniques to preserve it.
The underpinning of all this research is documentation. This means both accounting for un-documented or poorly documented past restorations, as well as elaborating upon existing references. Many of the MoMA paintings had minimal photographic documentation, which hinders the ability of conservators to identify changes to the work over time. The wealth of information gathered by the conservation and research team remains within the museum’s internal database, but there are plans to expand access to the project’s data. Having already worked in collaboration with many Dutch museums for access to their Mondrian collections, it’s clear to the MoMA team how a compiled database of all their research and documentation would be groundbreaking for the conservation and art history fields.