Whatever your take on modern art, it is hard to dispute the fact that all of its many well-known artists were original in their outlook, techniques, and artwork, none more so than one Paul Jackson Pollock (1912–1956).
Pollock is famed for his "drip painting" technique, which produced such artworks as "Number 19" from 1948, which sold at Christie's for a purported $58,363,750. Closer to our hearts as chemists, of course, is the 1947 painting "Alchemy", which has its home in the Peggy Guggenheim Collection, Venice, and is one of his earliest drip, or poured, paintings.
With this and other paintings, Pollock changed our perception of what being an artist means. He threw away the easel and brushes and instead used his whole being to pour emotion onto a canvas lying on the floor or propped against a wall, but only after long deliberation of its blankness. He poured and dripped streams of commercial paint onto the canvas from a can using a stick, and according to Guggenheim's Lucy Flint, "Pollock made obsolete the conventions and tools of traditional easel painting."
Of course, his technique was revolutionary, but he still used paint and it is the nature and composition of those paints that interests both heritage scientists and analytical chemists, who might reveal the hidden details of his art through their investigations. The latent data of a classic Pollock like "Alchemy" might then be used to provide the art world with the details of his process. Crucially for the possibility of future generations of lovers and critics of this art form, it could also inform conservation.
Costanza Miliani of the CNR Institute of Molecular Science and Technologies (ISTM) and the SMAArt, Centro di Eccellenza, Università di Perugia, Italy, and colleagues used recent advances in non-invasive and mobile spectroscopic methods based on point analysis and hyper(multi)-spectral imaging. They employed these methods to take a close look at "Alchemy" without the harmful effects of other analytical techniques that require a scraped or cut sample, for instance.
The researchers describe the painting as one of the most "materico" of Pollock's works, an Italian word meaning that the painting has a certain three-dimensionality to it rather than simply being a conventional, flat, 2D, artwork.They explain how Pollock built up layers of color on top of a previously dried layer. This means that each deposit is to an extent separated from the underlying layers, forming a complex stratigraphy with some intersection between colors. They also point out that Pollock's "palette" was extensive, comprising white to yellow, red, green, violet, blue, black, and silver.
In their investigation, the team combined point analysis with visible-near-infrared (Vis-NIR) multispectral imaging to peel back the layers of Pollock's abstract expressionism, figuratively speaking. "The molecular identification of pigments, colorants, and extenders contained in fifteen different paints has been achieved combining key spectral markers from elemental, electronic, and vibrational spectroscopies," the team reports. They add that for colors exhibiting similar hues but different chemical compositions, they used a mapping technique to compare the pigments with a false-color rendering. The team also used X-ray fluorescence (XRF) and Raman spectroscopy in their non-invasive study.
The main conclusions arising from the spectral lines point to the evolution of Pollock's drip and pouring technique. The team was able to identify the specific traditional oil-based paints and oil-modified alkyd media (synthetic polyester resins derived from alcohols and acids). In addition, point analysis by reflection Fourier-transform infrared spectroscopy (FTIR) scattered throughout the painting allowed them to map the traditional and new binding media among painted, squeezed, and dripped paints.
The team's techniques reveal Pollock's basic white pigment to be lead carbonate (lead white). However, the data also suggest the presence of titanium- and zinc oxide-based white pigments in other parts of the painting. The anhydrous form of calcium sulfate was also found to be present. The yellow paint, applied last, turned out to be cadmium and zinc sulfides. The UV-Vis-NIR reflection and emission properties suggest that the thick orange in the painting is due to a mixed cadmium sulfide-selenide pigment.
As to the red pigments, they are transparent to the X-ray study, but FTIR revealed an organic component: the azo β-naphthol pigment toluidine red. There is a tentative suggestion of a red anthraquinone-based compound present, too. Iron and manganese are present in the deeper reds and the violets of "Alchemy". Viridian is found in the greens, although the organic phthalocyanine green is also present. The related phthalocyanine blue is the main blue, although ultramarine blue was also found, apparently overlying a lead white base. Finally, the XRF data point to the blacks and silvers as being purely carbon black and aluminum, respectively.
"Alchemy" is an intricate and three-dimensional network of colors, the team concludes, and it was a near impossible task to establish the precise order of pigment application. Nevertheless, the team's non-invasive multi-technique method has revealed many details that would have remained hidden without their approach. The tool, they suggest, can acquire much information about a complex painting's chemistry and the palette used to create it.
"The work demonstrated that it is possible to get valuable information on the Pollock painting materials using non-invasive spectroscopic methods, Miliani told ChemViews Magazine. "This paved the way to study other Pollock's paintings to define how during the evolution of his technique the painter changed paint materials (pigments and binding media). The interest is in tracking the Pollock's technical "decisions" in the years around 1947, at the beginning of the drip period."
John Delaney is Senior Imaging Scientist at the National Gallery of Art, Washington DC, USA. He suggests that the work of the group in Perugia nicely demonstrates the progress made in the non-invasive analysis of complex works of art, such as Pollock's paintings. "Their findings help to extend the knowledge of the materials Pollock used while he was evolving his working method," he told ChemViews Magazine.
Delaney explained, "Prior work includes the identification and mapping of pigments in Pollock's earlier 1943 painting 'Mural', which was completed while the painting was at the Getty Center in 2012 to 2014. The findings in the Perugia work are relevant to our own recent analysis and mapping of the paint binders and pigments used in Pollock's 1950 drip painting entitled 'Number 1', here in the collection of the National Gallery of Art."
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