Judgment Day for Michelangelo’s Sistine Chapel Ceiling : Art: Most critics applaud the restoration of his Vatican masterpiece, but a minority terms it a rewriting of art history that is nothing less than a monumental disaster.

Persuaded by spiteful advisers that a headstrong young Florentine sculptor was overdue for comeuppance, Pope Julius II dragooned him into painting the vaulted ceiling of a new chapel at the Vatican.

Michelangelo Buonarroti reluctantly began the gigantic task on May 10, 1508. It was a punishment--and a challenge. Refusing assistance, he worked alone, by lantern light, standing with his head forced back at angles that soon damaged his eyesight.

What would become one of the world’s longest-running and most breathtaking displays of genius debuted on All Saints Day, Nov. 1, 1512. The Book of Genesis, in nine vibrant panels, had sprung to spectacular life across the 68-foot-high ceiling. In 1535, by then in his 60s, Michelangelo reluctantly returned to the Sistine Chapel to paint 391 figures on the wall behind the altar in “The Last Judgment.”

The results are history, and to these paramount works of art the Vatican is adding a codicil, with controversy, this spring.

After five years of painstaking, computer-aided restoration, the Sistine Chapel ceiling is complete and on show to visitors at the Vatican Museum. Expect big crowds: One day last summer, 19,000 visitors jostled to see the chapel even as restorers labored on scaffolds above them.

Now, new scaffolding is up in the chapel where the College of Cardinals elects Popes, and Tuesday restoration begins on the stormy “Last Judgment.”

Restoring the huge work will take about four years. It will be financed, like the rest of an in-stages chapel cleaning that has already consumed a decade, by a Japanese television network, NTV. In all, NTV will pay about $4.2 million in exchange for three years of exclusive pictures of the results after each stage of the cleaning.

To celebrate one of the century’s most ambitious art restorations, the Vatican has mounted an explanatory exhibition, entitled “Michelangelo and the Sistine Chapel: Technique, Restoration and Myth.”

The exhibition includes a selection of Michelangelo’s preparatory drawings for the chapel, a model of his scaffolding and a replica of how a segment of the ceiling looked as he prepared to paint it, with figures deliberately distorted atop so they would look lifelike from below. Videos and photographs explain the cleaning and restorative techniques and graphically describe the difficult art of fresco painting that Michelangelo learned, and mastered, high above the chapel.

His frescoes made Michelangelo a legend in his own time, and part of the exhibition is devoted to paintings and drawings, including works by Raphael, Rubens and Caravaggio, that highlight his impact on contemporary artists.

Located in the Braccio di Carlo Magno off St. Peter’s Square, the exhibition is open daily, except Wednesdays, through July 10. Entrance is 6,000 lire, about $5.

Together with the exhibition, the Vatican sponsored a weeklong, blue-ribbon symposium of about 60 of the world’s leading restorers, conservators and art historians. Their closed-door discussions ranged from how to preserve the restored frescoes to examining plans for the restoration of “The Last Judgment.”

The Vatican’s guests applauded the restoration, but there is a minority view--and thereby hangs the controversy.

Michelangelo’s hard-learned technique on the ceiling was to paint al fresco , which means that a patch of ceiling was freshly plastered for each day’s work. On the damp plaster, Michelangelo sketched his figures and filled them in with many fine coats of paint he had himself prepared. As the plaster, or intonaco , dried, the colors became bonded to it.

This, most experts believe in the wake of the restoration, left a work of great luminosity and bright color. Over the centuries, the original nature of the work was clouded, though, by an accumulation of grime, incense and candle smoke, and daubings and varnishes left by a procession of restorers.

To clean the ceiling, Vatican specialists used an Italian restorers’ standby: a diluted solution of ammonium bicarbonate, sodium bicarbonate, a fungicide and a gelling agent in water. Laid on with a soft brush, it was left in place only three minutes and then carefully sponged away.

From the cleaning emerged the multi-hued, bold, light-celebrating ceiling that greets visitors to the chapel today. Michelangelo’s masterpiece seems to reach down and grab the viewer with the vivacity of its color and the strength of its larger-than-life figures.

It is, most critics are saying with delight, a Michelangelo of a brilliance and clarity never seen before. One early visitor, Pope John Paul II, called the restoration an undertaking of “universal significance and value.”

For a few naysayers, though, the restoration of Michelangelo’s monument displays not Michelangelo at all, but a rewriting of art history that is nothing less than a monumental disaster.

They argue that too-abrasive restoration stripped away not only the dirt, but also much of the painting’s depth by eliminating shadows that Michelangelo created by retouching his work a secco --after the plaster was dry.

Vatican restorers flatly reject the assertion, saying that the artist was prevented from much retouching by the demands of a Pope anxious to show off the chapel. What few areas of overpainting Michelangelo did, the restorers say, were protected during the cleaning and remain as he left them.

“We removed dirt. We didn’t remove Michelangelo,” restoration director Febrizio Mancinelli insists.

The loud conflict of experts has ricocheted through the art world for more than a decade already. And it appears it will intensify now that dark-to-light restoration is about to begin on “The Last Judgment,” which is revered as one of mankind’s crowning artistic achievements.