VATICAN CITY (RNS) – “The Last Judgment,” Michelangelo’s vast fresco painted into the plaster of the Vatican’s Sistine Chapel is undergoing an extraordinary maintenance process in preparation for Easter, with a team of 20 restorers working in two shifts a day remove a thin milky residue that has built up due to the thousands who come to admire the masterpiece every day.

Barbara Jatta, director of the Vatican Museums, described the coating as “a sort of cataract” to journalists on Saturday (Feb. 28) that flattens the dramatic effect of shadows and light of the roughly 45-by-40-foot fresco.

After it was discovered two years ago, laboratory tests revealed that the coating primarily consisted of calcium lactate, a type of salt formed from the breath of the 17,000 to 20,000 daily visitors to the chapel, where the church’s cardinals convene to elect a pontiff. Seven million people passed through the space last year.

“Calcium lactate comes from respiration, the increase in temperatures, humidity, and also the increase in the number of visitors,” explained Fabrizio Biferali, the curator of 15th–16th Century art at the Vatican Museums.

Michelangelo created the most famous image in the chapel, the Creation of Adam, in which God and the first man extend their fingers toward the other, in 1508, 25 years after the first Mass was said in the completed chapel. In 1533, Pope Clement VII commissioned “The Last Judgment” for the altar wall, though Michelangelo did not begin painting until 1536 under Pope Paul III, who named him “Supreme Architect.” 

The fresco — a form of art in which pigments are applied to wet plaster, rather than painted onto dry walls — fills nearly 2,000 square feet of wall, with a staggering 391 figures tumbling and recoiling from Christ’s Second Coming and final judgment at the end of time.

Using delicate Japanese tissue, the restoration team applies deionized water to the fresco, dissolving and removing the salt deposit within minutes. “This is not a restoration, nor is it a cleaning intervention,” Jatta explained, while adding that the work will allow the colors to return to the vibrancy they had when Michelangelo completed them in 1541.

“Every time we work, we discover new details of his technique — how he reasoned, how he resolved questions of volume and drawing. For us, he is still present,” said Angela Cerreta, vice chief restorer. “As we gradually remove this white veil and see things more clearly, we always notice something new. The emotion continues, every day.”

The project is funded by the Florida Chapter of the Patrons of the Arts in the Vatican Museums, which, along with other chapters contributes to the restorations and upkeep of the museums. Mary Viator, chair of the Florida Chapter, said the group, which has helped financed the restoration of the Pauline Chapel and other parts of the Vatican, was moved to be a part of “The Last Judgment” project because of its religious, artistic and cultural relevance, according to statement by the museums.  

Alberto Albanesi, vice administrative director of the Vatican Museums, did not disclose an official cost for the project, but said that one of the biggest items on the budget goes to the specially designed scaffold, which allows visitors to continue circulating while the fresco is worked on. The scaffold is covered by a curtain showing a high resolution rendition of “The Last Judgment.”

The work, which began in mid-January, is due to finish at the end of March, in time for Pope Leo XIV’s first Holy Week and Easter celebrations as pontiff. The last major restoration of the Sistine Chapel, which included full scale cleaning and conservation, took 14 years, beginning in 1980 and ending in 1994.

With rising temperatures and increasing numbers of visitors every year, Cerreta said, the chapel requires constant monitoring and maintenance to preserve the fresco for future generations. 

“We have been monitoring the environment of the Sistine Chapel since 2009,” Marco Maggi, who heads the Office of the Conservator at the Vatican Museums, adding that the chapel’s strictly monitored climate maintained at 71.6 to 75.2 degrees Fahrenheit and 55% to 60% humidity.

While the frescoes have stood centuries, the numbers of visitors means that the museum has to streamline their path through the chapel to ensure that the room doesn’t become too crowded, putting the art at risk. “The challenge is to find a balance between accessibility and conservation,” Jatta said.