By using an electron microscope and X-ray fluorescence spectrometry, which reveals the parts of pigments without taking invasive samples, researchers found that early on van Gogh used perspective frames as a guide and drew on the canvas to correctly render proportions and depth of field in his landscapes. Later, as he gained mastery, he abandoned these grids. Like many artists, he reworked certain paintings repeatedly to perfect his desired effect. The most important insight was into his palette, said Nienke Bakker, curator of the show.

“We now know much more about the pigments van Gogh used and how they might’ve changed color over time,” Ms. Bakker said. “That’s crucial to our understanding of his works, and to know better how to treat them. The colors are still very vibrant, but they would have been even brighter — especially the reds. Some of the reds were much brighter or have completely disappeared since he painted them.”