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.”

Ralph Haswell, principal scientist at Shell Global Solutions here, which made its lab facilities and researchers available to the museum, said that at the turn of the 20th century artists had just started buying pigments off the shelf rather than mixing them in the studio. “One of the disadvantages of living in a very changing environment where pigments were very new was that they didn’t always know how things would turn out,” he said. “The chemical industry was growing hugely and they came up with all kinds of colors, but you never knew how long they would remain stable. Some pigments weren’t stable.” That was the case with van Gogh’s violet, used to depict the walls of his room in Arles. Because the red in the purple paint faded prematurely, probably even during van Gogh’s lifetime, it left behind only the blue with which it had been mixed.

That may have been fine with van Gogh, Ms. Bakker said, since the largely self-taught artist didn’t regard any of his work as final. He saw pieces as studies that helped him find his style.