Lasers vs. grime: Park service says treatment wiped out Jefferson Memorial’s black film

A close-up view showing the dome of the Jefferson Memorial before and after the laser-abatement treatment. The dome has been plagued by the grimy, black coating known as a biofilm for the past several years. (Courtesy National Park Service)
A close-up view showing the dome of the Jefferson Memorial before and after the laser-abatement treatment. The dome has been plagued by the grimy, black coating known as a biofilm for the past several years. (Courtesy National Park Service) (Courtesy National Park Service)
A worker uses the laser-abatement treatment to clean the Jefferson Memorial's biofilm. (Courtesy National Park Service)
A worker uses the laser-abatement treatment to clean the Jefferson Memorial’s biofilm. (Courtesy National Park Service) (Courtesy National Park Service)
Photos provided by the National Park Service show the effect of the laser-ablation treatment on the dome of the Jefferson Memorial. The uncleaned portion of the dome, covered in the film, is at the bottom of the photo. (Courtesy National Park Service)
Photos provided by the National Park Service show the effect of the laser-ablation treatment on the dome of the Jefferson Memorial. The uncleaned portion of the dome, covered in the film, is at the bottom of the photo. (Courtesy National Park Service) (Courtesy National Park Service)
A view of the biofilm on the exterior of the Jefferson Memorial. (Courtesy National Park Service)
A view of the biofilm on the exterior of the Jefferson Memorial. (Courtesy National Park Service) (Courtesy National Park Service)
This photo shows the black growth that began coating the sides of the Jefferson Memorial more than a decade ago. The biofilm - a combination of bacteria, fungi and algae, has spread more rapidly in recent years and this week the National Park Service applied various chemical agents to a section of the marble to see if any would remove the film. (WTOP/Nick Iannelli)
This photo shows the black growth that began coating the sides of the Jefferson Memorial more than a decade ago. The biofilm — a combination of bacteria, fungi and algae — has spread more rapidly in recent years. (WTOP/Nick Iannelli) (WTOP/Nick Iannelli)
A biofilm has blackened sections of the roof line of the Jefferson Memorial. The National Park Service describes the film as a combination of bacteria, fungi and algae growing on the marble of the landmark.  (WTOP/Nick Iannelli)
A biofilm has blackened sections of the roof line of the Jefferson Memorial. The National Park Service describes the film as a combination of bacteria, fungi and algae growing on the marble of the landmark. (WTOP/Nick Iannelli) (WTOP/Nick Iannelli)
The National Park Service has posted this sign outside the Jefferson Memorial last August explaining to the public that a microbial substance is growing on the 73-year-old landmark, turning the marble black. (WTOP/Nick Iannelli)
The National Park Service has posted this sign outside the Jefferson Memorial last August explaining to the public that a microbial substance is growing on the 73-year-old landmark, turning the marble black. (WTOP/Nick Iannelli) (WTOP/Nick Iannelli)
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A close-up view showing the dome of the Jefferson Memorial before and after the laser-abatement treatment. The dome has been plagued by the grimy, black coating known as a biofilm for the past several years. (Courtesy National Park Service)
A worker uses the laser-abatement treatment to clean the Jefferson Memorial's biofilm. (Courtesy National Park Service)
Photos provided by the National Park Service show the effect of the laser-ablation treatment on the dome of the Jefferson Memorial. The uncleaned portion of the dome, covered in the film, is at the bottom of the photo. (Courtesy National Park Service)
A view of the biofilm on the exterior of the Jefferson Memorial. (Courtesy National Park Service)
This photo shows the black growth that began coating the sides of the Jefferson Memorial more than a decade ago. The biofilm - a combination of bacteria, fungi and algae, has spread more rapidly in recent years and this week the National Park Service applied various chemical agents to a section of the marble to see if any would remove the film. (WTOP/Nick Iannelli)
A biofilm has blackened sections of the roof line of the Jefferson Memorial. The National Park Service describes the film as a combination of bacteria, fungi and algae growing on the marble of the landmark.  (WTOP/Nick Iannelli)
The National Park Service has posted this sign outside the Jefferson Memorial last August explaining to the public that a microbial substance is growing on the 73-year-old landmark, turning the marble black. (WTOP/Nick Iannelli)

WASHINGTON — A high-tech method using lasers to clean a grimy black coating on the Jefferson Memorial’s dome has proved so successful, officials now want to give the rest of the monument a laser scrub-down, the National Park Service said Tuesday,

The park service partnered with the Chicago-based conservation firm Conservation of Sculpture and Objects Studio last month for a four-week trial run of the laser-ablation treatment.

Park service officials are “very satisfied” with the laser treatment’s performance during the testing, architectural conservator Justine Bello said in a statement.

“The level of clean that was achieved exceeded our expectations,” she said in the statement. “We were able to clean the stone in a safe manner that protected both this cultural resource and the surrounding natural environment as well.”

The laser treatment eradicated the unsightly black coating on about 1,000 square feet of the 10,682 square feet that make up the memorial’s dome, the park service said.

“When the scaffolding is down, it will be very noticeable,” National Park Service spokesman Mike Litterst told WTOP. “If you think of the dome as sort of a pie, there’s going to be a slice out of that darkened area that will be back to the brilliant white that we were used to so many years ago.”

The black coating — known as a biofilm — is made up of a colony of microscopic organisms that sticks to stone surfaces and has been slowly overtaking the monument for the past several years.

Last year, park service officials began searching for a cleaning solution that would be able to remove the biofilm without damaging the monument’s historic marble or using harsh chemicals that would harm the surrounding environment.

“It’s very strong, it’s very difficult to get rid of,” Litterst said. “And the treatment of biofilm on historic structures is still sort of in its infancy, so we were sort of experimenting and trying to find the best possible way to go about and treat this problem.”

The park service aims to use the laser treatment to remove the rest of the biofilm from the memorial next year alongside a related project to rehabilitate the memorial’s roofs. But that depends on whether the park service gets the full funding for the project officials have requested.

WTOP’s Megan Cloherty contributed to this report.


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