The Hidden Story of Smalt in Rembrandt's Homer

Between 2012 and 2018, researchers worked on a project called REVISRembrandt, which focused on Rembrandt's late painting technique (1651-1669). One interesting fact about his late paintings is his extensive use of smalt, a blue cobalt glass pigment that he often mixed with other colors. Over time, many of these smalt-containing paints have changed color, which led researchers to question what the paintings originally looked like and why Rembrandt used smalt. "Homer" (1663) by Rembrandt, located in the Mauritshuis in The Hague, was studied using a combination of techniques such as macroscopic X-ray fluorescence imaging (MA-XRF) with computational analysis and SEM-EDX analysis of paint cross-sections. These methods provided new insights into the distribution and composition of smalt paints in the artwork.

Researchers also recreated paint mixtures to see how different amounts of smalt affected the overall color, drying time, translucency, and texture of the paint. They found that in high smalt concentrations or when mixed with more transparent pigments, the paint became cooler and darker. Adding opaque pigments reduced the translucency of the smalt. Another surprising discovery was that smalt-containing paints dried five times faster than those without. The texture of the paint was also significantly influenced by the addition of smalt, creating a more textured surface with clear brushstrokes. Optical coherence tomography (OCT) was used to reveal differences in translucency and texture between the different paint reconstructions. In conclusion, smalt played a crucial role in Rembrandt's late paintings, not for its blue color, but for adding volume and texture, deepening colors, and speeding up drying time.

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