Washington, Oct. 3 (ANI): The age-old mystery about why ultramarine blue colour fades may have been solved, with scientists at New York University and Pratt Institute having found that upon colour degradation, the framework of this colour breaks apart, and releases the colour-forming molecules.

For their study, Alexej Jerschow, an assistant professor of chemistry at NYU, Eleonora Del Federico, an associate professor of chemistry at Pratt Institute, and their co-workers examined ultramarine pigments obtained from the semi-precious stone lapis lazuli, one of the most valued pigments by European painters since the late 13th century.

They say that the intense blue colour is formed by small molecules made up from sulfur trapped in the framework of these pigments, which is made up of aluminium and silicon atoms.

The researchers measured the nuclear magnetic resonance (NMR) signals of the aluminium and silicon atoms in the framework to determine the concentration of these colour-forming molecules, and analysed fresco samples stored under accelerated degradation conditions.

They found that the ultramarine pigment framework structures break apart and set free the colour-forming molecules.

Jerschow says that by understanding the process by which ultramarine blue fades will help them conduct further researches to identify proper art conservation techniques.

Apart from the scientific interest in this work, these activities have created an exciting opportunity for both science and arts students to transcend discipline boundaries, said Jerschow.

These unique investigations promise to have tremendous impact on our understanding and prevention of the chemical processes that underlie the slow-often irreversible-decay of our cultural heirlooms, he added. (ANI)