Restoration begins on 17th-century Rembrandt painting The Night Watch

Researchers and restorers at Amsterdam's Rijksmuseum launched a months-long project Monday, using high-tech imaging technology to throw new light on Rembrandt van Rijn's 17th-century painting The Night Watch.

The three-million euro ($4.4-million Cdn) effort is expected to take about a year, museum director Taco Dibbits said.

That is due not only to the fame of the painting, which dates from 1642, but also to its size, as the canvas measures 3.63 by 4.37 metres and weighs 337 kilograms.

The painting will remain in its usual spot at the end of the Gallery of Honour in the Rijksmuseum, and visitors will be able to watch from behind a glass wall as experts restore it.

Art lovers around the world can follow the project online.

Painted over several years, The Night Watch was commissioned as a group portrait of an Amsterdam city militia and broke new ground by showing its subjects in action rather than as a static portrait.

Experts argue over whether it was intended as a night scene or whether it is simply perceived as such because of Rembrandt's use of shadows pierced by light.

The painting last underwent significant restoration 40 years ago after it was slashed by a knife-wielding man and is starting to show blanching in parts of the canvas.

The painting has undergone many retouches and restorations in the past and some of the later additions are starting to fade.

X-rays, digital images

Before the latest restoration can begin, experts will photograph and scan the painting to evaluate its condition.

They will build up a detailed digital picture by merging 12,000 separate images as well as using X-ray technology to peer through the surface.

On Monday, a macro X-ray fluorescence scanner began taking a series of images, said Petria Noble, head of paintings conservation at the Rijksmuseum.  

"Each type of technique will give us some information that we then need to put together and interpret all the information together and what that means for the painting." Noble said. 

"This is the first time that we can actually make a full body scan and that we can discover which pigments he used not only through making little samples but with scanning the entire surface," Dibbits said.

"We don't know much about how Rembrandt made this painting. And now we hope to discover more and really get a glimpse into the kitchen of the artist." 

More than two million people each year visit the Rijksmuseum, which has the world's largest collection of Rembrandt works. The Golden Age master is known for his innovative use of light and rebellious compositions.

The restoration project comes in a year that marks the 350th anniversary of the artist's death in 1669 and is part of a "Year of Rembrandt" at the museum.