VATICAN CITY (AP).- An ambitious project to clean the statue-topped colonnade that cradles St. Peter's Square is likely to last at least three more years, the director of the Vatican restoration says.

The work on Gian Lorenzo Bernini's columns began in 2009, after some two years of preliminary studies, and it is proceeding in sections so the square can still be used for Vatican events, including papal appearances.

Guy Devreux, who directs the Vatican's workshop for marble and limestone structures, spoke to The Associated Press during a tour that included a close-up look from atop scaffolding.

He said the work, which also involves cleaning two fountains and Egyptian obelisk, is arranged so the square is always accessible to tourists who flock year-round and especially as Easter approaches.

The tradition of outdoor papal audiences, like the crowded one Benedict XVI led in the square on Wednesday, continues without interruption.

Being restored are 140 statues and 284 columns. Bernini's colonnade is a double one, with an inner row and outer row, with each one consisting of two side-by-side columns.

The first task was removing any fragment that seemed at risk of detaching, Devreux said.

Restorer Alessio Tagnani said the work involves first removing any algae, lichen and moss that has formed on the stone over time.

Cleaning can involve mechanical methods, such as a hammer and a scalpel, abrasive-acting micro-sanders, or the gentle application of chemicals with a compress.

"For a restorer in a laboratory like mine in the Vatican Museums, this is a master's work," Devreux said. "Not just because it is monumental but because it was created by Bernini itself."

He estimated it will take at least three more years to complete the project, and he compared it to another project at the Vatican.

"You could say it is like our Sistine Chapel," the hall frescoed by Michelangelo that is part of the Museums tour and the gathering place to elect popes, he said.

Restoration in the 1980s and 1990s of the Sistine Chapel, including its fabled frescoed ceiling, took decades and was heavily criticized by some who were startled by the vivid hues that emerged from under five centuries of grime, dust and candle smoke.

Pope Alexander VII gave the colonnade commission to Bernini, master of Baroque architecture in Rome in the 17th century who also did the canopy sculpture over the main altar in St. Peter's Basilica.

The colonnade's construction helped provide employment for many people as Rome was emerging from a plague epidemic, Devreux said. "For this reason, he wanted to fix up the square, giving work to many people who in that period were jobless."


Copyright 2012 The Associated Press.