If only Vincent van Gogh (1853−1890) had been able to afford canvas, the world would have many more of the master’s paintings. But as scholars have long known, van Gogh re-used his canvasses, especially when he wasn’t happy with a painting, creating a new work on top of an old one. These hidden compositions have mostly eluded art historians because current museum-based imaging tools cannot properly visualize them.

But European researchers now say they have a way to reveal the covered-over paintings in unprecedented detail, finding the van Goghsunder the Van Goghs. In the first use of the technology, they report in the online issue of Analytical Chemistry, they have discovered a woman’s head hidden under van Gogh’s "Patch of Grass."

Since scholars estimate that one-third of van Gogh’s paintings were covered over, the technology—called synchrotron radiation-based X-ray fluorescence mapping—could reveal a whole new world of the master’s works that have remained invisible to earlier techniques, notably X-ray radiation transmission radiography. XRR mostly picks up heavy metals in paint pigments, such as lead in lead white or mercury in vermillion. Since van Gogh’s “do overs” usually started with a primer coat of lead white to cover up the original image, XRR often produces few recognizable details. Under"Patch of Grass," for instance, XRR revealed the vague outlines of a head, but no facial characteristics, making the person portrayed unidentifiable.

Scientists led by Joris Dik of Delft University of Technology in The Netherlands thought they could do better. They transported Patch of Grass to the synchrotron light source at the HASYLAB, part of the particle physics lab DESY in Hamburg, Germany. After bombarding the painting with the radiation, they write, “we succeeded in visualizing the hidden face with unprecedented detail."

The technique picked up and identified mercury and antimony in the red (vermillion) and light (Naples yellow) pigments, respectively, letting the scientists see the flesh tones, the brushstrokes and all the facial details—eyes, nose, mouth, and chin. They could even see “the reddish intensity of the flesh tones of the lips, cheek, and forehead,” they report:

“The hidden painting dovetails with an extensive series of heads from the artist’s period in Nuenen (The Netherlands). Between October 1884 and May 1885 he painted the heads of peasant models in the dark settings of their huts, in the neighborhood of the village of Nuenen. . . . The present head must belong to a smaller group of studies that Vincent gave to his brother Theo in Paris, as mentioned in his letters (Some of the heads I promised you are finished, but they are not quite dry yet; I should like to hear whether those rolled-up things arrived safely). After 2 1/2 years, Vincent went to join Theo in Paris and may very well have found the woman’s head hopelessly old-fashioned by then. This, together with his uncomfortable financial situation, can explain the presence of a colorful, Parisian style floral painting on top of a dark and sombre head of a provincial Dutch woman.”

Here she is: