A group of preservation experts were waxing historic on a celebrated subject Thursday, coating the inside of the Liberty Bell to protect it from environmental pollutants and the fingerprints of tourists who can't resist touching the Colonial-era icon.
A technician applied a new layer of microcrystalline wax to the interior of the 2,080-pound bell, a procedure that is performed once or twice a year.
The outside of the bell has been given a variety of coatings over the decades that seem to protect it well. It's a different situation inside the bell, however, where stagnant air traps airborne contaminants that can erode the pitted cast bronze alloy surface.
Conservators first noticed a white powdery buildup developing inside the bell about 30 years ago and consulted with experts at the Philadelphia Museum of Art, said Park Service staff curator Bob Giannini.
A chemical analysis identified the salt-like substance as ammonium sulfate _ possibly coming from fertilizer being applied to flowers just outside the building or from ammonia-based cleaners that were used on the windows.
Since then, technicians have applied the protective wax to the bottom eight inches of the bell's interior. Each time, the old coating is heated and removed before the new wax layer is applied and buffed, Giannini said.
Before opening hours Thursday morning, technician Jonathan Miller took to the task for about 40 minutes, leaving the bell freshly protected from pollutants and a wayward.
"There was a time when people could touch the bell," Giannini said. "It's not something (visitors) have been allowed to do for a long time, but it happens."
The bell was created to commemorate the 50-year anniversary of William Penn's 1701 Charter of Privileges, Pennsylvania's original constitution. Years later, abolitionists around the nation adopted it as a symbol for the movement to end slavery.
Historians disagree on when it first cracked. It was last rung to celebrate George Washington's birthday in 1846.