Impressionist paintings are known for their vibrant colors and unique brushwork, but over time, these colors can begin to fade. One noticeable issue is the loss of bright yellow hues in paintings from the late 19th and early 20th centuries. Some of the iconic paintings, such as Edward Munch’s “The Scream” and Henri Matisse’s “The Joy of Life,” are now showing signs of discoloration. The culprit behind this color change is the chemical compound cadmium sulfide, which was commonly used by many European artists during this period.
Researchers at Duke University have developed a new laser microscopy technique to detect the early signs of pigment decay in paintings. This non-invasive method allows conservators to identify color changes before they become visible to the naked eye. By using ultra-fast pulses of light, the researchers can create 3D maps of the pigments and monitor their degradation at a microscopic scale. In a recent study published in the Journal of Physics: Photonics, the researchers applied this technique to samples of cadmium yellow paint.
In the lab, the researchers subjected samples of cadmium yellow paint to an artificial aging process to simulate the effects of light and humidity on the pigments. Through pump-probe microscopy, they were able to track the degradation progress on a microscopic scale. The results showed that even before the color changes were visible, clear signs of decay were already present in the data. Moisture triggered the transformation of cadmium sulfide into cadmium sulfate, resulting in a whitish or dull cast on the paint.
While the primary focus of the research is on art conservation, the implications of this study extend beyond the preservation of paintings. By studying the degradation of cadmium yellow in century-old paintings, researchers can gain insights into modern materials that are vulnerable to similar environmental elements. For example, cadmium sulfide is used in solar cells, and understanding how it degrades over time can lead to improvements in the durability of these technologies.
Although the current technique is not easily replicable outside of a laboratory setting, the researchers are working on developing a more portable version that can be used by conservators in museums. This new tool could help identify color changes in paintings early on and allow for interventions to slow down or stop the deterioration process. While irreversible color loss cannot be undone, early detection can help preserve the integrity of these works of art for future generations.