In recent years, X-ray imaging has revealed overpainted underdrawings, details and drafts in works by such luminaries as Vermeer, Artemisia Gentileschi, Edgar Degas, René Magritte, Pablo Picasso and Rembrandt.

Now, a 16th-century religious painting is set to join the ranks of these multi-layered masterpieces: Per a press release, art conservators from England’s Northumbria University recently discovered a hidden nativity scene while conducting an X-ray scan of a damaged canvas depicting Saint John the Baptist’s beheading.

The nativity scene before (left) and after (right) conservators added markings revealing the painting's one-time appearance. (Northumbria University/Bowes Museum)

The long-forgotten artwork shows the baby Jesus lying in a manger, surrounded by a halo-crowned angel, one of the three wise men, and a figure who may be a shepherd, according to Metro’s Harrison Jones. The outline of a building believed to be a stable can be seen in the background.

“It really is quite unusual to find paintings hidden in this way,” says Nicky Grimaldi, a conservation expert who helped identify the painted-over scene, in the statement.

Grimaldi and her colleagues initially assessed the canvas—acquired by John and Joséphine Bowes, founders of the local Bowes Museum, during the 19th century—to determine how much damage it had sustained since its creation some 400 years ago.

Little is known about the painting’s past, but the press release states it was crafted in the late medieval style and probably belonged to a larger altarpiece. Like other works from the period, the canvas, which finds the Christian saint clasping his hands (presumably in a prayer seeking salvation prior to execution), is mounted on a large wooden panel. It has suffered significant paint loss over the centuries, particularly at the spots where the backing’s oak, pine or chestnut planks are joined together.

To begin the conservation process, the team carried out an X-ray analysis of the beheading scene.

“That,” says Grimaldi, “was when we realized there was more to the painting than we originally thought.”

Baby Jesus before (left) and after (right) conservators added markings revealing the painting's one-time appearance. (Northumbria University/Bowes Museum)

As the Northumbria conservator explains, gold leaf used to accentuate the infant Christ’s halo is visible in X-ray views of the underlying nativity scene. Lines copied onto the canvas from a preparatory drawing, or cartoon, also appear, darkened with a type of lead paint visible on X-ray.

The team’s findings add to, rather than elucidate, the mysteries surrounding the canvas. Experts are unsure when the nativity was painted or why it was subsequently covered up, and the name of the artist—or artists—who created the scenes may never be known.

Still, additional assessment conducted by Grimaldi and forensic scientist Michelle Carlin may offer some of the answers to these questions, or at least provide more insights on the work’s age, background and history. Moving forward, the researchers plan on conducting a chemical analysis of the paint used in the scenes, drawing on tools including a scanning electron microscope, energy-dispersive X-ray spectroscopy and infrared reflectography.

A figure believed to be one of the three wise men before (left) and after (right) conservators added markings revealing the painting's one-time appearance. (Northumbria University/Bowes Museum)

Jon Old, a conservator who cleaned the canvas several years ago, tells the Guardian’s Amy Walker he noticed markings indicative of a hidden underpainting when removing varnish from the John the Baptist scene.

“I thought it would be a fun thing for the students to look into so we donated it to the university,” says Old. “It’s quite a rare find. I only found out a month ago about the nativity scene, but it’s really quite fascinating.”