10/11/2013 03:39 EDT | Updated 01/23/2014 06:58 EST

World's most frequently stolen piece of art gets a facelift

Five years ago, Ron Spronk dropped into Saint Bavos Cathedral in the small Flemish town of Ghent.

The canon of the cathedral took him aside. His pride and joy, the Ghent Altarpiece, part of the cathedral for nearly 600 years, was not in good shape. It was warping, the paint was lifting. The priest was not happy.

“It was not just the canon,” says Spronk, a professor of art history at Queen’s University in Kingston, Ont. “The entire town really cares about this painting.

“It really is part of Ghent, part of the community.”

The Ghent Altarpiece has been labeled a Flemish cultural icon. It is venerated by art historians and a mainstay of Belgium’s tourist industry. Visitors climb off tour buses every day and line up for their 10 minutes with a guide in front of the altarpiece.

Painted by Hubert and Jan van Eyck, it was completed in 1432. Art historians consider it one of the first and finest examples of realist painting in northern Europe, but it has had a rocky history. The Ghent Altarpiece has been looted by armies, stolen by thieves and dragged across Europe.

Belgium was in danger of losing it. Experts from all over the world pored over the altarpiece, and the decision was made to undertake a multimillion-Euro facelift.

And Ron Spronk, a man with an international reputation in the technical examination of paintings, became part of the restoration team.

A technical miracle

Comprised of 20 wooden panels 17 feet wide by 15 feet high, the altarpiece is a series of portraits of saints and biblical scenes.

At the time it was completed, it was considered a technical miracle. The realism of the images makes it seem as though Adam is about to step into the world of the viewer; God appears to be staring the viewer right in the eyes.

“Even for us, it is a complete revelation,” says Spronk. “Just imagine how it would have been for the people in the 15th century. They must have been blown away.”

The alterpiece sat quietly amazing people in Saint Bavos Cathedral for a century. Then came the wrath of the Reformation. Newly minted Protestants rioted against the opulence and corruption of the Catholic Church. They built a bonfire of church art that could be seen for 10 miles, but the people of Ghent had hidden the altarpiece safely in the town hall.

Later on, it was looted by Napoleon’s armies and taken to the Louvre in Paris. The new French king gave the altarpiece back, but then the church sold off the side panels to pay for repairs to the roof of the cathedral.

Those side panels, which amount to more than half of the altarpiece, ended up in a museum in Berlin for a century.

Belgium got them back as reparations from Germany at the end of the First World War; the Ghent Altarpiece is specifically included in the Treaty of Versailles.

Germany never got over the loss, and Hitler targeted the altarpiece. The church spirited all 20 panels away through France en route to the Vatican. But the government of Vichy France gave up the hiding place and the Ghent altarpiece joined thousands of pieces of art hidden by the Nazis down in the salt mines in Austria.

It was recovered by the American army in 1945 and helicoptered back to Belgium.

Ravaged by history

The altarpiece was battered but had survived the ravages of history. Ironically, it was the attention of well-meaning caregivers 25 years ago that nearly destroyed it completely.

In the interest of security, it had been placed behind thick bulletproof glass in the cathedral. Spronk calls it a bunker; others call it “the aquarium.” At any rate, the condensation caused the wood to warp and the paint to lift.

Major restoration work was essential. But Ghent’s sense of attachment to the altarpiece was so strong that it had to be kept in public view even while it was being restored.

In the dead of night, under police protection, the first few panels were moved from the cathedral to the Museum of Fine Arts in Ghent. The canon watched them go.

“He was crying,” says Bart de Volder, the on-site coordinator of conservation.

Now, De Volder and the seven other restorers work behind a glass wall in the museum, where the public can watch them as they wipe away centuries of grime and coats of varnish and touch up the spots that previous restorations have destroyed.

“Art historians used to keep everything to themselves. Here, we decided to open it all up,” says de Volder.

But despite these efforts, it’s likely no one will ever see the Ghent altarpiece in its entirety again. Back in 1934, two of the panels were stolen. Only one was recovered.

“Up to this point, police are still looking for it,” says de Volder.

While there is currently a copy in place of the missing panel, Spronk says that “every year, there are rumours that the original is going to resurface, and that creates a real buzz.”