Specialists are using lasers to clean up the black biofilm on the Jefferson Memorial dome.
The biofilm was first noticed in 2006.
“Biofilm is a microbial community of algae, fungi and bacterial growth,” National Park Service historical architect Audrey Tepper said.
In recent years, various removal methods were tested, and lasers were chosen as the best option.
“These are not lasers from ‘Star Wars,’” Tepper said. “These are lasers that are designed for architectural surfaces.”
The laser work is done inside protective tents.
“The laser is very laborious; it’s very precise,” Tepper said.
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Arlington Cemetery, the Lincoln Memorial and some of the Smithsonian buildings have it, too.
“Actually, it’s a fairly common phenomenon, and you will see biofilms in different forms throughout Washington, D.C.,” Tepper said.
It’s worse at the Jefferson Memorial because the bacteria thrives in sunlight and moisture.
“This is just such an exposed location,” Tepper said.
Removing the biofilm is only part of the $8 million, 15-month renovation. Repairs are being made inside as well, including fixing the roof to the portico, which has been deteriorating due to water damage.
The memorial remains open to tourists during the project.