As they painstakingly scrape grime off a monumental painting by French artist Gustave Courbet, the restorers do a remarkable job of ignoring their unusual surroundings: They're watched by crowds of people, many recording on mobile phones.

Paris' Orsay Museum has thrown open to the public a process that often happens behind closed doors.

The cleaning and repairs to "A Burial at Ornans," one of the museum's signature works that Courbet painted between 1849 and 1850, are taking place in a bespoke enclosure with windows for visitors to peer through.

"A great idea," said Jennifer Dasal, a visiting art historian from North Carolina. "If it’s lasting for a while, people can come back and they can watch the restoration over time."

The restoration is expected to take about a year. The painting hasn't had a major overhaul for about 50 years. Layers of varnish that yellowed over time have dulled Courbet's colors. The weight of the huge work has deformed its frame, and its canvas has stitching, folds and tears that need attention.

The museum also plans free guided tours of their work for those who register on its website, with three time slots every Thursday morning from June 5.