Researchers Find Why Ultramarine Blue Fades 2 October 2006

Researchers find why ultramarine blue fades 2 October 2006

The 20-year restoration of Michelangelo's frescoes color is formed by small molecules made up from on the ceiling of the Sistine Chapel has left visitors sulfur trapped within this framework. The in awe of the work's original majesty--notably the researchers found that upon color degradation the brilliance of the blue that graces the Last framework breaks apart and releases the color- Judgment's sky. Recent investigations into this forming molecules. shade of blue--ultramarine blue--have brought to light the pigment's tendency to fade. Is it possible The research team reached this conclusion by that the longevity of such a masterpiece as the measuring the nuclear magnetic resonance (NMR) Last Judgment could be in peril? signals of the aluminum and silicon atoms in the framework. This method is akin to magnetic Researchers at New York University and Pratt resonance imaging, but is used by chemists to Institute now have the answer to why it fades, understand the structure and geometry of which gives the art world direction on how to molecules and materials. This procedure allowed protect the works of past and future masters. the researchers to determine the concentration of these color-forming molecules. Similar analysis of The natural ultramarine pigment, obtained from the fresco samples stored under accelerated semi-precious stone lapis lazuli, has been one of degradation conditions revealed that the the most valued pigments by European painters ultramarine pigment framework structures break since the late 13th century. Before the 19th apart and set free the color-forming molecules. century, the only known source of lapis lazuli was Understanding the process by which ultramarine in the quarries of Badakhshan (northeastern blue fades will allow further research to identify Afghanistan), a site visited and described by Marco proper art conservation techniques. Polo. He wrote: "There is a mountain in that region where the finest azure [lapis lazuli] in the world is "Apart from the scientific interest in this work, these found. It appears in veins like silver streaks." Lapis activities have created an exciting opportunity for lazuli provided not only a vibrant blue color both science and arts students to transcend unmatched by any other pigment available at the discipline boundaries," said Jerschow. "These time, but it added a divine nature to the artwork in unique investigations promise to have tremendous which it was used. Since it was valued more highly impact on our understanding and prevention of the than gold, its use typically conveyed the high chemical processes that underlie the slow--often status of a work's commissioner. Ultramarine was irreversible--decay of our cultural heirlooms." the pigment often reserved to paint the mantel of the Virgin Mary. The research on ultramarine pigments is part of a larger collaborative initiative among the NYU Instances of fading of ultramarine pigments are Chemistry Department, Pratt Institute, and the known, but the mechanism of color alteration of the Metropolitan Museum of Arts' associate research pigments is not understood--a process that served scientist Dr. Silvia Centeno. The research team is as the focal point of the researchers' study. In their currently also investigating the origin of lead-white work, Alexej Jerschow, an assistant professor of flaking in illuminated manuscripts and lead-soap chemistry at NYU, Eleonora Del Federico, an formation in traditional oil paintings. associate professor of chemistry at Pratt Institute, and their co-workers examined ultramarine An important aspect of this work is related to pigments, which are made up from frameworks of bringing the experimental techniques right into aluminum and silicon atoms. The intense blue museums, a revolutionary step that will allow

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researchers to analyze delicate material onsite so as to maximize conservation while protecting unique works of art.

Source: New York University

APA citation: Researchers find why ultramarine blue fades (2006, October 2) retrieved 25 September 2021 from https://phys.org/news/2006-10-ultramarine-blue.html

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