MYSTERY SOLVED: JACKSON POLLOCK USED MANGANESE BLUE IN FAMOUS 1948 PAINTING | MOMA and SOLOMON LAB

Scientists discover and characterize previously unidentified pigment in the artist's palette

Jackson Pollock’s famous painting Number 1A, 1948 looms large, both physically (it measures 172.7 by 264.2 cm) and in the history of modern art. But the blue pigment that Pollock used in the painting had been something of a mystery, until now.

Researchers led by Abed Haddad, a conservation scientist at the Museum of Modern Art (MoMA) in New York City, and Edward I. Solomon, an inorganic chemist at Stanford University, have definitively identified manganese blue as the pigment in the painting. The scientists also analyzed the chemical to figure out what underlying phenomena give the pigment its blue hue (Proc. Natl. Acad. Sci. U.S.A. 2025, DOI: 10.1073/pnas.2513166122).

About a decade ago, conservation scientists at MoMA used macro-X-ray fluorescence mapping to study the pigments in Number 1A, 1948. That study identified the pigments in the red and yellow paints and detected the key elements of manganese blue—manganese, barium, and sulfur. But the scientists couldn’t say for sure that manganese blue was the pigment used. That’s because the elements detected can also come from salts and fillers used in paints. Also, the technique that the scientists used isn’t great at identifying organic pigments that could instead have been responsible for the blue color.

Enter Haddad, an expert in Raman spectroscopy—a technique that identifies chemical structures using the scattering of laser light. Haddad took a microsample of the blue paint from the back of the canvas of Number 1A, 1948, and “through Raman spectroscopy, I was able to pinpoint that it is in fact manganese blue,” he says.

To better understand what gives the pigment its blue color, Haddad reached out to Dean Lahana, who had been an undergraduate at the City College of New York when Haddad was doing his doctoral studies there. Lahana, who had moved to Stanford for graduate school, told Haddad that he didn't specialize in the kind of work Haddad was looking for but that it would be a great project for his roommate, Alexander J. Heyer, a graduate student in Solomon’s lab.

Solomon is well known for using spectroscopic methods to probe metalloenzymes and, more recently, heterogeneous catalysts. Solomon and Heyer used a combination of resonance Raman spectroscopy (a souped-up form of Raman spectroscopy), magnetic circular dichroism, and density functional theory calculations to probe the pigment.

Chemically speaking, manganese blue is made of manganate(VI) centers scattered throughout a barium sulfate lattice. The researchers found that the blue color arises from electrons bouncing from the oxide ligands to the manganese metal ion in two ways, which cause two absorption bands to arise—one in the green part of the spectrum and one in the purple. The trough between them is the blue color seen in manganese blue.

Heyer notes that stabilizing the oxo ligands on the manganate could shift those two bands, thereby changing the color. “You could potentially dope metal ions into different lattices to fine-tune color to get very specific pigments,” he says.

But it’s unlikely that manganese blue will ever be manufactured again. The pigment was discontinued in the 1990s because of environmental and health concerns over the way it’s made. Nevertheless, the new study will help art conservation scientists identify the pigment in other works. “The extent to which it landed in the artists’ palette we don't quite know yet,” Haddad says.

Heyer says that “this study is unique in how it blends two areas that don’t always overlap.” Not only does the study identify a pigment that’s important for art conservation, he says, it also provides a thorough physical inorganic chemistry analysis on the nature of the pigment’s color.

Karen Trentelman, head of technical studies at the Getty Conservation Institute, who was not involved in the work, says in an email that the paper provides “a lovely example of the synergy between the artistic process and the molecular processes responsible for color.” She says she is always on the lookout for “the opportunity to take what may at first appear to be a routine analytical finding into a deeper understanding of an underlying chemical or physical process. It all stems from being curious.”