X-ray fluorescence (XRF) and fiber optics reflectance spectroscopy (FORS) were instrumental in determining the locations of now-faded smalt. The map at left depicts areas of the painting where smalt is present. Bruegel only used it mixed with other pigments. Blue indicates areas containing (1) smalt and iron oxide. Yellow indicates areas containing (2) smalt, iron oxide, and vermilion. Red indicates areas containing (3) smalt and cochineal.
In the digital simulations below, I rendered each pigment combination slightly differently:
1. Smalt and iron oxide. Since iron oxide pigments can range from yellow to red to brown, we cannot be certain of the intended hue of the iron-containing areas of the painting. Depending on the iron oxide, the resulting color could have leaned toward green, purple, or brown. Visual examination suggests the presence of a red iron oxide, but the chemical alteration of smalt may have caused optical effects in these areas. Still, the digital simulations assume that the iron oxide pigment was fairly red in color. Thus the color of the final mixture would have been blue or reddish blue, depending on the amount of smalt used.
2. Smalt, iron oxide, and vermilion. Keeping in mind the iron oxide issue noted above, these areas were likely reddish blue—a mixture of two reds and blue.
3. Smalt and cochineal. Bruegel applied a translucent red lake, cochineal, over the blue smalt. These areas were probably lavender.
All images © 2019, Detroit Institute of Arts, Conservation Department, all rights reserved
Faded smalt in The Wedding Dance
Published in Bulletin of the Detroit Institute of Arts 93, no. 1 (2019), 136-8