The audience watches as conservators carefully restore a Rembrandt masterpiece to its former glory

Visitors to the Rijksmuseum in Amsterdam looking at one of Rembrandt’s most known paintings, The Night Watchchange before their eyes. Behind a glass barrier, conservators remove the painting’s old varnish as it hangs on the gallery wall – the first step in the masterpiece’s restoration.

The 12.5 by 15 foot Rembrandt painting is being restored as part of Operation Night Watchthe Rijksmuseum’s ongoing study of the 17th-century Dutch masterpiece. During the five-year research phase of the project, experts re-stretched the canvas and examined the physical components of the painting, discovering arsenic sulfide pigments behind the golden glow and lead in the base layer. The second phase of Operation Night Watch began this month when eight conservators began removing it varnish—clear, protective layers often applied to paintings.

“The paint that is on it now The Night Watch is discolored, yellowed and poorly saturated, which really affects the legibility of the paint surface,” says restorer Ige Verslype in one video from the Rijksmuseum. “To treat this we need to remove the old paint. And you also see many old, discolored retouches on the paint surface. They are often applied very broadly and cover the original paint. So we want to remove them and apply new, fine retouches.”

The Night Watch has undergone several repaints: one in 1975, after a man cut the artwork with a bread knife; one in 1981; and one in 1990, after another man sprayed the painting with acid, reports Agence France-Presse (AFP).

“Former restoration projects went very quickly,” said the director of the Rijksmuseum Taco Dibbits tells AFP. The current restoration involves the application of a new layer of varnish, bringing the painting “as close as possible to its former glory,” he adds.

Completed in 1642, The Night Watch shows a group of citizens guards—The 17th-century local police force of Amsterdam. Rembrandt painted The Night Watch at the height of his career, and it is known for the artist’s masterful treatment of light and shadow.

Conservators are cleaning The Night Watch by applying small pieces of tissue, each lightly soaked in solvent, to the surface of the painting, Verslype says. “This removes most of the old paint.” Then, using cotton swabs, they remove the remaining remnants of older varnish.

“I think the most exciting and perhaps the scariest thing is that people are looking over our shoulders,” says the curator Esther van Duijn tells AFP. “But once you start working, you often forget that.”

Where the varnish has been removed, the painting looks matte and “very grayish,” says Verslype. As Dibbits says in a statement“It will be a truly unique experience for the visiting public to be able to follow the process so closely.” He tells AFP: “You will be able to see it The Night Watchin a sense naked, without make-up.”

For a conservator, removing the varnish from a painting is “an absolute privilege”. Paula Dredgea conservationist at the University of Melbournetells the WashingtonPost‘s Kelsey Ables. It is “a moment of contact with the artist’s creation that very few people experience.”

Dredge adds that the restoration is a “process of discovery,” in which “we may find more of Rembrandt.” She praised the museum’s decision to open the operation to visitors.

“Collections in public institutions belong to the people, and they have the right to know what is being done to them,” she says.