"We really have to get this sorted out when you think about the important cultural heritage that has the potential to be damaged," Mass said last week.
Mass, also an adjunct assistant professor of art conservation at the University of Delaware, was speaking not just about the Matisse, which was completed in 1906 and titled Le bonheur de vivre in the original French. Various forms of deterioration have been reported in numerous works from the late 19th and early 20th centuries by such luminaries as Monet, van Gogh, Picasso, and Seurat, as some of the bold new pigments they used have turned out to be unstable.
These pigments, developed during the Industrial Revolution, provided the artists with some of the striking colors that defined their work. Especially important were new forms of yellow, made with cadmium and chromium, said Francesca Casadio, senior conservation scientist at the Art Institute of Chicago.
Whereas the Old Masters were limited to ochers and golds, the new generation of painters wielded yellows that ranged from light primrose greens to warm orangey hues.
"Everything they were doing was about light, and painting outside in the light and being able to capture these colors in the light," Casadio said.
Casadio was not involved with the Matisse study but said she was familiar with it, characterizing it as an extremely complicated bit of detective work.
Mass enlisted the help of Rutgers, Cornell, and Stanford Universities and the University of Delaware. She was joined in her efforts by Barnes scholars Barbara Buckley and Margaret Little.
Mass said the Matisse analysis, funded by the Mellon Foundation, was not conducted because of the impending move of the Barnes collection to Philadelphia. But she said the timing was good because the findings would help the museum arrange proper light and humidity settings for The Joy of Life, which is to have its own special gallery.
The painting is now hung in a stairwell leading to the second floor of the Barnes Foundation's current gallery in Merion, but it is not on public view. The stairwell and second floor were closed in January so conservators could begin preparing for the move.
The first floor of the gallery in Merion remains open until early July. After that, the next time the public can see the collection is May 2012, when the new gallery opens on the Benjamin Franklin Parkway.
The scientific analysis of the Matisse began with a handheld device that measures X-ray fluorescence - a standard technique that provided a quick reading of where cadmium- and chromium-based pigments were located in the painting.
The team then moved on to a tongue-twisting array of more high-tech tools to identify and quantify specific chemical compounds. Among the techniques: infrared spectroscopy, X-ray absorption near-edge spectroscopy and X-ray photoelectron spectroscopy.
The last of those, done at Rutgers with equipment the size of several refrigerators lined in a row, allowed the team to see how the paint surface had changed composition after exposure to light and oxygen, Mass said.
The researchers aimed a narrow X-ray beam at a flake of paint that had been removed from an inconspicuous spot in the painting - a sample smaller than a period on this page.
The X-ray beam caused the flake to emit electrons of various kinetic energies, which the scholars measured to determine the compounds present, said Rutgers physicists Robert Bartynski and Sylvie Rangan.
But the process reveals the composition of only the merest surface of a substance, so Mass had to turn the paint flake sideways to measure how its profile changed between the outermost, exposed layer and the part that had been near the canvas.
For example, one of the yellows Matisse used was made from cadmium sulfide but has gradually converted to cadmium sulfate and cadmium carbonate, which are more whitish in color, Mass said.
"We can actually see the cadmium carbonate growing in at the surface," Mass said. "The amount of cadmium sulfide, which is yellow, is getting smaller and smaller over time."
During the 19th century, the quality of cadmium yellow varied from batch to batch because of imperfect manufacturing processes at the time, she said. A smaller, postcard-size version of The Joy of Life, also owned by the Barnes, contains the same pigment but shows no signs of degradation, Mass said.
Elsewhere in the big version of the painting, different shades of yellow have either darkened or begun to flake off - processes the team is still studying. The Barnes already has used a polymer solution to adhere the flaking paint back in place, Mass said, praising the museum for its efforts since the problems were first identified in the 1990s.
Much of the painting's color scheme remains unchanged, including a chromium-based lemon yellow near a circle of dancers.
Once the painting is in its own gallery in Philadelphia, the museum may use lights of a specific wavelength to minimize further oxidation, she said.
In the future, some chemical treatments might be considered to reverse the color changes, but that would be considered an invasive treatment and would be undertaken only with extreme care, she said.
It is of the utmost cultural importance to maintain the work for posterity, she said, and not just for everyday museumgoers. In recent years, she said, even some art scholars have been led astray in their written commentaries, failing to realize that some of the bold, original colors have been lost.
"I think Matisse is not getting a fair deal at the moment," Mass said. "What art historians are looking at is not his original vision."
Contact staff writer Tom Avril at 215-854-2430 or firstname.lastname@example.org.